阅读说明：本技术 一种高电磁兼容和可靠性的逆变空气等离子切割机 (Inverter air plasma cutting machine with high electromagnetic compatibility and reliability ) 是由 蔡献 魏继昆 蔡庆乐 陈法庆 朱宣辉 朱宣东 于 2020-06-03 设计创作，主要内容包括：本发明涉及一种高电磁兼容和可靠性的逆变空气等离子切割机,切割机电路板包括大控制板、主控制小板和高频控制板；大控制板上安装的零部件包括主控制小板和高频控制板；主控制小板通过连接件直接焊装在大控制板上；高频控制板通过插头及其控制线与大控制板部分的电路进行连接；整个控制电路主要由输入滤波电路、上电缓冲电路、逆变主电路、输出滤波电路、开关电源电路、IGBT驱动电路、电流检测和整流变换电路、热保护检测和控制电路、电流给定电路、电磁阀控制电路、引弧控制电路、输出特性控制电路、电流显示电路、高频切断控制电路组成；本发明采用控制硬件和软件抗干扰措施,较好解决了切割机高电磁兼容性和可靠性的问题。(The invention relates to an inversion air plasma cutting machine with high electromagnetic compatibility and reliability.A circuit board of the cutting machine comprises a large control board, a main control small board and a high-frequency control board; the parts arranged on the large control panel comprise a main control small plate and a high-frequency control panel; the main control small plate is directly welded on the large control plate through a connecting piece; the high-frequency control board is connected with a circuit of the large control board part through a plug and a control line thereof; the whole control circuit mainly comprises an input filter circuit, an upper electricity buffer circuit, an inverter main circuit, an output filter circuit, a switching power supply circuit, an IGBT drive circuit, a current detection and rectification conversion circuit, a thermal protection detection and control circuit, a current setting circuit, an electromagnetic valve control circuit, an arc striking control circuit, an output characteristic control circuit, a current display circuit and a high-frequency cut-off control circuit; the invention adopts the anti-interference measures of control hardware and software, and better solves the problems of high electromagnetic compatibility and reliability of the cutting machine.)

1. The utility model provides an contravariant air plasma cutting machine of high electromagnetic compatibility and reliability which characterized in that: comprises a shell part of the cutting machine and an internal circuit part, a metal plate and an output connecting plate, wherein the metal plate comprises a handle or a combined handle, a shell bottom plate, a front panel, a rear panel and a control panel; the internal circuit part mainly comprises an input filter circuit, an upper electricity buffer circuit, an inverter main circuit, an output filter circuit, a switching power supply circuit, an IGBT drive circuit, a current detection and rectification conversion circuit, a thermal protection detection and control circuit, a current setting circuit, an electromagnetic valve control circuit, an arc striking control circuit, an output characteristic control circuit, a current display circuit and a high-frequency cut-off control circuit; the circuits are arranged on three circuit boards inside the cutting machine, wherein the three circuit boards are respectively a large control board, a main control small board and a high-frequency control board; the parts arranged on the large control panel comprise a main control small plate and a high-frequency control panel; the large control panel also comprises an inversion main transformer, an IGBT pipe group I, IGBT radiator I, CBB capacitor, an IGBT radiator II, a driving transformer, an electrolytic capacitor, a common mode inductor, a switching power supply transformer, an IGBT pipe group II, a rectifier, a current transformer, an overheat protector, a main control small plate, a high-frequency control panel, a rectifier tube I, an output filter reactor, a rectifier tube radiator I, a rectifier tube radiator II and a rectifier tube I; the main control platelet comprises a PWM pulse width modulation integrated circuit chip, an operational amplifier, a resistor, a capacitor, a diode and a voltage regulator tube; the high-frequency control board comprises a high-voltage boosting transformer, a spark amplifier, a high-voltage ceramic chip capacitor, a relay, a resistor, a capacitor, a diode and a plug connector or a socket; the main control small plate is directly welded on the large control plate through a connecting piece; the high-frequency control board is connected with a circuit of the large control board part through a plug and a control line thereof; the large control board is vertically installed on the bottom board of the casing, and the small control board circuit is mainly an output characteristic control circuit.

2. The inverter air plasma cutter with high electromagnetic compatibility and reliability as claimed in claim 1, wherein: the input filter circuit consists of two common-mode inductors, a resistor and a plurality of capacitors, wherein the capacitor 7C7 is connected in parallel at two ends of the rear stage of the power switch S1 of the cutting machine, the rear stage of the capacitor is connected with the common-mode inductor 7MT1, the rear stage of the common-mode inductor 7MT1 is connected with the resistor 7R1 and the capacitor 7C5 in parallel, one end of the common-mode inductor 7MT1 is connected with the capacitor 7C3, the other end of the common-mode inductor 7MT1 is connected with the capacitor 7C4, and the other ends of the capacitor 7C3 and the capacitor 7C4 are connected to the ground end; the rear stage of the common mode inductor 7MT1 is connected with the common mode inductor 7MT2, the rear stage of the common mode inductor 7MT2 is connected with the capacitor 7C6 and the input end of the rectifier BD1 in parallel.

3. The inverter air plasma cutter with high electromagnetic compatibility and reliability as claimed in claim 1, wherein: the output filter circuit part comprises a filter inductor LX, a plurality of resistors, a plurality of filter capacitors, a voltage dependent resistor 9VR2, a voltage dependent resistor 9VR3 and a plurality of diodes; the resistor 9R1 is connected in series with the filter capacitor 9C1, and then connected in parallel with both ends of the output rectifying fast recovery diode 9D1, similarly, the resistor 9R2 is connected in series with the filter capacitor 9C2, and then connected in parallel with both ends of the output rectifying fast recovery diode D6; the resistor 9R3 is connected in series with the filter capacitor 9C3 and then connected in parallel with two ends of the output rectifying fast recovery diode 9D 3; the resistor 9R4 is connected in series with the filter capacitor 9C4 and then connected in parallel at two ends of the output rectifying fast recovery diode D8; the four diodes form a full-wave rectification circuit, and the input end of the full-wave rectification circuit is connected in parallel with the two ends of the secondary output winding of the inverter main transformer T11; the resistor 9R5 is connected in parallel with the two output ends of the full-wave rectifying circuit; the negative end of the full-wave rectification circuit is connected with a filter inductor LX, and a series circuit consisting of a resistor 9R6, a capacitor 9C5, a plug 9CN1, a diode 9Z1, a diode 9Z2, a diode 9Z3 and a diode 9VR2 is connected between the other end of the filter inductor LX and the output positive polarity end of the full-wave rectification circuit in parallel; the series circuit is characterized in that three positive polarity diodes 9Z1, 9Z2 and 9Z3 are connected in series, the anode end of the diode 9Z1 is connected with the positive output polarity end of the full-wave rectification circuit, the cathode of the diode 9Z3 is connected with the diode 9VR2, and the diode 9VR2 is connected with the LX filter inductor and one end of the output high-frequency coupling transformer T2; the other end of the output high-frequency coupling transformer T2 is connected with a negative output end; the output positive polarity end of the full-wave rectification circuit is also connected to the positive output end, and meanwhile, the output positive polarity end of the full-wave rectification circuit is also connected to one ends of a diode 9VR3 and a filter capacitor 9C6, and the other ends of the diode 9VR3 and the filter capacitor 9C6 are connected to the grounding end of the cutting machine; the primary end of the output high-frequency coupling transformer T2 is connected to the high-frequency arc striking circuit board through a connecting wire.

4. The inverter air plasma cutter with high electromagnetic compatibility and reliability as claimed in claim 1, wherein: the switching power supply circuit part consists of a switching power supply transformer T4, an optical coupler U11, an optical coupler U28, a switching power supply PWM control chip U30, a field effect transistor U29, a plurality of integrated voltage regulators, and resistors, capacitors and voltage regulators around the integrated voltage regulators, the switching power supply circuit comprises an input part and a high-voltage side circuit part, a filter capacitor C59 and a filter capacitor C60 are connected between a direct-current bus voltage +310V and the ground in parallel, the two ends A and B of the direct-current bus voltage +310V are connected between a rack or protective ground, the end A is connected with a capacitor C57 and a capacitor C60, a resistor R76 and a resistor R77, the dotted terminal of a main primary winding of a switching power supply transformer T4 is connected in parallel, the capacitor C57 and the resistor R76 are connected in parallel, the other end of the direct-current bus voltage +310V is connected with the cathode of a diode D30, the anode of the diode D30 and the dotted terminal of a main primary winding of the switching power supply transformer T4 are connected with the D terminal of a U29, and the other end of the resistor R77 is connected with a pin 7 of a switching power supply PWM control chip U30; the capacitor C56 and the resistor R79 are connected in parallel, one end of the capacitor C56 is connected with the end B, which is also the ground end of the input high-voltage part of the switching power supply circuit, and the other end of the capacitor C56 is connected with the pin 7 of the PWM control chip U30 of the switching power supply; the S end of the field-effect tube U29 is connected with a resistor R71 and a resistor R72, the other end of the resistor R71 is connected with the ground end of the input high-voltage part, the other end of the resistor R72 is connected with a pin 3 of a switching power supply PWM control chip U30, and a capacitor C53 is connected in parallel between the pin 3 of the switching power supply PWM control chip U30 and the ground end of the input high-voltage part; a capacitor C54 is connected in parallel between the 4 feet of the switching power supply PWM control chip U30 and the ground end of the input high-voltage part; a capacitor C55 is connected in parallel between the 8 pins of the switching power supply PWM control chip U30 and the ground end of the input high-voltage part; a resistor R73 is connected between the pin 8 and the pin 4 of the switching power supply PWM control chip U30; a pin 5 of the switching power supply PWM control chip U30 is connected with the ground end of the input high-voltage part; a pin 6 of the switching power supply PWM control chip U30 is connected with a resistor R74, and the other end of the resistor R74 is connected with the G end of a field-effect tube U29; a capacitor C51 and a resistor R75 which are connected in parallel are connected between pins 1 and 2 of the switching power supply PWM control chip U30; a pin 2 of a switching power supply PWM control chip U30 is connected with a resistor R69, the other end of a resistor R69 is connected with a resistor R68 and an emitter of an output stage triode in an optocoupler U28, and the other end of a resistor R68 is connected with the ground end of an input high-voltage part; the collector of an output triode in an optocoupler U28 is connected with a pin 7 of a U30 chip and an R70 resistor, the other end of the R70 is connected with the anode of a C52 electrolytic capacitor and the cathode of a D29 diode, the cathode of the electrolytic capacitor C52 is connected with the ground end of an input high-voltage part, the anode of the diode D29 is connected with the synonym end of an auxiliary winding of a switching power supply transformer T4, and the synonym end of the auxiliary winding of the switching power supply transformer T4 is connected with the ground end of the input high-voltage part; in the output part and the low-voltage side circuit part of the switching power supply circuit, the secondary side of the switching power supply transformer T4 has two windings, one is an independent secondary winding, and the other is a secondary winding with a center tap; for the secondary winding with a center tap, two windings of the secondary winding are connected in series in positive polarity, namely the synonym end of one winding is connected with the synonym end of the other winding, which is also called a common connection point, the connection point is also the ground end of a power supply voltage, the connection ground end divides the two windings into an upper winding and a lower winding, the synonym end of the upper winding is connected with the cathode of a diode D27, a capacitor C4 and an electrolytic capacitor C48 are connected in parallel between the anode of a diode D27 and the common connection point or the ground, the anode of the electrolytic capacitor C48 is connected with the ground end, the anode of a diode D27 is connected with the input end of an integrated voltage stabilizer 7915, the ground end of the integrated voltage stabilizer 7915 is connected with the common connection point or the ground, a capacitor C2 and an electrolytic capacitor C7 are connected in parallel between the output-15V of the integrated voltage stabilizer 7915 and the anode of the electrolytic capacitor C7 is connected with the ground end; the unlike end of the lower winding is connected with the anode of a diode U27, a capacitor C12 and an electrolytic capacitor C21 are connected in parallel between the cathode of the diode U27 and a common connection point or the ground, the cathode of the electrolytic capacitor C21 is connected with the ground, the anode of a diode U27 is connected with the input end of an integrated voltage stabilizer 7815, the ground end of the integrated voltage stabilizer 7815 is connected with the common connection point or the ground, a capacitor C30 and an electrolytic capacitor C19 are connected in parallel between the output +15V of the integrated voltage stabilizer 7815 and the ground, and the cathode of the electrolytic capacitor C19 is connected with the ground; the anode of the diode U27 outputs +24V between the ground, and the +24V power supply supplies the cooling Fan Fan and the relay JR1 to work; the anode of the diode U27 is connected with the cathode of a voltage regulator tube Z5, the anode of a voltage regulator tube Z5 is connected with a resistor R67, the other end of the resistor R67 is connected with the anode of an input-stage light-emitting diode in an optocoupler U28, the cathode of the input-stage light-emitting diode in the optocoupler U28 is grounded, and a capacitor C50 is connected between the anode of the input-stage light-emitting diode in the optocoupler U28 and the ground; and for the independent secondary winding and the output power circuit part thereof, the power supply is mainly used for supplying power for the cutting gun switch control circuit.

5. The inverter air plasma cutter with high electromagnetic compatibility and reliability as claimed in claim 1, wherein: the cutting gun switch control circuit part is as follows: one end of a cutting gun switch S is connected with a filter inductor L1, the other end of the cutting gun switch S is connected with a filter inductor L2, the other end of a filter inductor L2 is connected with the cathode of a diode D26, an electrolytic capacitor C18, the anode of an electrolytic capacitor C20, a resistor R18 and a capacitor C11, the anode of a diode D26 is connected with the synonym end of a secondary independent winding of a switching power supply transformer T4, the other end of the filter inductor L1 is connected with a resistor R11, a capacitor C13, the cathode of a diode D3 and the other end of a capacitor C11, the other end of a resistor R11 is connected with the anode of a light emitting diode in an optocoupler U11, and the cathode of the light emitting diode in the optocoupler U11, the other ends of the capacitor C13, the capacitor C18, the resistor R18 and the cathode of the electrolytic capacitor C20 are connected with the synonym end of the secondary independent winding of the switching power supply transformer T4.

6. The inverter air plasma cutter with high electromagnetic compatibility and reliability as claimed in claim 1, wherein: the IGBT driving circuit part is divided into a low-voltage side driving circuit and a high-voltage side driving circuit, 4 IGBTs are arranged in the inverter circuit part, 4 high-voltage side IGBT driving circuits are arranged, and the form of each high-voltage side driving circuit is consistent; the driving transformer T3 has 4 independent secondary windings, and the IGBT driving circuit is divided into a low-voltage side driving circuit and a high-voltage side driving circuit through the driving transformer T3; the cathode of a fast recovery diode D601 of the high-voltage side driving circuit is connected with a resistor R601 and the same-name end of one secondary winding of a driving transformer T3, the anode of the fast recovery diode D601 is connected with a resistor R605, the other end of the resistor R605 is connected with the other end of the resistor R601 and is connected with the G1 grid of an IGBT1, the different-name end of the secondary winding of the driving transformer T3 is connected with the E1 drain of the IGBT1, and a capacitor C601 is connected between the G1 and the E1 poles of the IGBT1 in parallel; similarly, the cathode of the D602 fast recovery diode is connected with the R602 resistor and the synonym terminal of the other secondary winding of the driving transformer T3, the anode of the D602 is connected with the resistor R606, the other end of the resistor R606 is connected with the other end of the resistor R602 and is connected with the G2 gate of the IGBT2, the synonym terminal of the secondary winding of the driving transformer T3 is connected with the E2 drain of the IGBT2, and the capacitor C602 is connected in parallel between the G2 and the E2 poles of the IGBT 2; the cathode of the fast recovery diode D604 is connected with the resistor R604 and the dotted terminal of the other secondary winding of the driving transformer T3, the anode of the fast recovery diode D604 is connected with the resistor R608, the other end of the resistor R608 is connected with the other end of the resistor R604 and is connected with the G3 grid of the IGBT3, the dotted terminal of the secondary winding of the driving transformer T3 is connected with the E3 drain of the IGBT3, and the capacitor C604 is connected between the G3 and the E3 poles of the IGBT3 in parallel; the cathode of the fast recovery diode D603 is connected with the resistor R603 and the synonym end of the other secondary winding of the driving transformer T3, the anode of the fast recovery diode D603 is connected with the resistor R607, the other end of the resistor R607 is connected with the other end of the resistor R603 and is connected with the G4 grid of the IGBT4, the synonym end of the secondary winding of the driving transformer T3 is connected with the E4 drain of the IGBT4, and a capacitor C603 is connected between the G4 and the E4 poles of the IGBT4 in parallel; the IGBT low-voltage side driving circuit consists of a plurality of field effect transistors, a plurality of resistors, a plurality of capacitors, an electrolytic capacitor C45, an electrolytic capacitor C6 and a primary winding of a driving transformer T3; the two ends of an electrolytic capacitor C6 are provided with a +15V power supply, a capacitor C29 is connected in parallel between +15V and the ground, one end of a resistor R58 is connected with +15V, the other end of the resistor R58 is connected with the D ends of a field effect transistor Q6 and a field effect transistor U23, the anode of the capacitor C69, the anode of the electrolytic capacitor C69, the capacitor C69 and the capacitor C69, the other end of the capacitor C69 and the cathode of the electrolytic capacitor C69 are grounded, the other end of the capacitor C69 is connected with the S end of the field effect transistor U69, the D end of the field effect transistor U69 and the capacitor C69 are grounded, the other end of the capacitor C69 and the S end of the field effect transistor Q69 are grounded, the S end of the field effect transistor Q69 and the D end of the capacitor C69 are connected with the S end of the field effect transistor Q69, the other end of the capacitor C69 and the S end of the capacitor C69 are connected with the resistor C8472 and the primary winding of the resistor R69 which are connected in parallel with the driving circuit of the transformer Q69, the other end of the primary winding of the driving transformer T3 is connected with the S end of the field effect transistor U23 and the D end of the field effect transistor U24; the G end of the field-effect tube Q6 is connected with a resistor R62, the G end of the field-effect tube Q8 is connected with a resistor R63, the G end of the field-effect tube U23 is connected with a resistor R60, the G end of the field-effect tube U24 is connected with a resistor R61, the other ends of the resistor R62 and the resistor R63 are connected, and the other ends of the resistor R60 and the resistor R61 are respectively connected with a pulse width signal output end of a PWM chip U2 on the main control platelet.

7. The inverter air plasma cutter with high electromagnetic compatibility and reliability as claimed in claim 1, wherein: the output characteristic control circuit part consists of a PWM chip U2, a plurality of operational amplifiers, a voltage regulator tube Z1, a plurality of diodes, a plurality of resistors and a plurality of capacitors on the periphery of the diodes; the circuit composed of the operational amplifier U1D and the operational amplifier U1C is a synchronous follower, a pin 9 of the operational amplifier U1C is connected with a pin 8 thereof, a pin 10 of the operational amplifier U1C is connected with a pin 8 of the PWM chip U2, a capacitor C7 and a capacitor C8, the other ends of the capacitor C8 and the capacitor C8 are grounded, the pin 8 of the operational amplifier U18 is connected with one end of a series circuit of the capacitor C8, the resistor R8 and the capacitor C8, the other end of the series circuit of the resistor R8 and the capacitor C8 is connected with the other end of the capacitor C8 and the other end of the resistor R8, and is connected to the pin 4 of the PWM chip U8, the resistor R8 and the resistor R8, the other end of the resistor R8 is grounded, the other end of the resistor R8 is connected with the output end of a rectifying bridge of the current detection circuit, and the other end of the resistor R8 is connected with the control terminal of the PWM chip 8, and the other end of the resistor R8 is connected with the ground of the resistor U8 and the control terminal of the resistor U8, the other end of the resistor R9 is connected with + 15V; the 12 pin of the operational amplifier U1D is connected with a resistor R5, a resistor R6 and a capacitor C4, the other ends of the resistor R6 and the capacitor C4 are grounded, the other end of the resistor R5 is connected with the cathode of a diode D3 and the resistor R4, the anode of a diode D3 is grounded, and the other end of the resistor R4 is connected with the output 1 pin of the operational amplifier U1A; the pin 13 of the operational amplifier U1D is connected with the pin 14 thereof, and is simultaneously connected with a resistor R7, the other end of the resistor R7 is connected with a capacitor C5 and a pin 5 of the PWM chip U2, and the other end of the capacitor C5 is grounded; a pin 1 of the PWM chip U2 is connected to a resistor R15, the anode of an electrolytic capacitor C13, a resistor R16, and a collector of an output triode in a U18 optical coupler, the other ends of the resistor R15 and the electrolytic capacitor C13 are grounded, the other end of the resistor R16 is connected to a pin 2 of the PWM chip U2, the anode of an electrolytic capacitor C11, and a pin 5 of the operational amplifier U1B, the other end of the electrolytic capacitor C11 is grounded, a pin 6 of the operational amplifier U1B is connected to a resistor R18, a resistor R19 and a capacitor C12, the other ends of the resistor R12 and the capacitor C12 are grounded, the other end of the resistor R12 is connected to +15V, a pin 7 of the operational amplifier U1 12 is connected to the anode of a diode D12, the cathode of the diode D12 is connected to a resistor R12, the other end of the resistor R12 is connected to a connection end of the capacitor C12, the resistor R12, and a turn-off control end of a pin 16 of the PWM chip U12; the 3 pin of the PWM chip U2 is grounded; the 4 pins of the PWM chip U2 are connected with a capacitor C9, a capacitor C4, a resistor R12, a resistor R10, a resistor R11 and a resistor R14; the pin 6 of the PWM chip U2 is connected with the pin 7 thereof; the 12 pin of the PWM chip U2 is grounded, the 13 pin of the PWM chip U2 is connected with the positive electrode of the electrolytic capacitor C16 and the electrolytic capacitor C17, the resistor R23, the other ends of the capacitor C16 and the electrolytic capacitor C17 are grounded, and the other end of the resistor R23 is connected with the 15 pin of the PWM chip U2U2 by + 15V; the pin 3 of the operational amplifier U1A is grounded, and two diodes D1 and D2 which are connected in an inverted manner are connected in parallel between the pin 2 of the operational amplifier U1A and the pin 3 of the operational amplifier U1A; the 2 pin of the operational amplifier U1A is connected with the anode of a voltage regulator tube Z1 and a resistor R3, the cathode of the voltage regulator tube Z1 is connected with the 1 pin of the operational amplifier U1A, the other end of the resistor R3 is connected with a capacitor C1, the other end of the capacitor C1 is connected with the 1 pin of the operational amplifier U1A, the 1 pin of the operational amplifier U1A is connected with the resistor R4, the resistor R5 and the cathode of a diode D3; the circuit formed by the operational amplifier U1A is a PI operation control circuit, and the circuit formed by the operational amplifier U1B is a voltage comparator.

Technical Field

The invention relates to a structure and a circuit of an inverter air plasma cutting machine with high electromagnetic compatibility and reliability. Belongs to the technical field of inversion air plasma cutting machines.

Technical Field

At present, the market competition of the inverter type air plasma cutting machine products is very strong, and the inverter type air plasma cutting machine not only reflects the advancement and the advantages of the technology, but also depends on the aspects of the functions, the design and the like of the cutting machine to a great extent.

In the markets at home and abroad, the rated current of the small inverter type air plasma cutting machine is usually 20-40A (the load duration rate is 15-100% and the like). Different products have different control circuit principles, circuit board structures and overall structure designs. In addition, there is a large difference in reliability and electromagnetic compatibility of products. Some products have very poor reliability, and almost 100% of repair rate. Some products, though not having such a high rework rate, nearly half of the products fail. For the problem, the user has strong response, the product complaints are many, and the user is difficult to accept. Through market research, the main reasons for such product failure problems are: the control circuit of the cutting machine is unreliable in operation. Due to the fact that the control circuit and the control scheme are not designed reasonably, control failure and faults are serious. For the electromagnetic compatibility of products, most of the products do not satisfy the EMC electromagnetic compatibility certification requirement and obtain the certification certificate, so that the market admission requirement with the electromagnetic compatibility certification in the european union, the united states and the like is difficult to satisfy. Therefore, how to solve the above problems and develop a cutting machine with high electromagnetic compatibility and reliability is a problem that many people in the electric welding machine industry pay attention to together and is also a problem to be solved by the invention. The invention adopts a new technical scheme of anti-interference measures of control, hardware and software, and better solves the problems of high electromagnetic compatibility and reliability of the cutting machine.

The power supply of the cutting machine is single-phase 220-240V, has the function of an air plasma cutting process method, and meets the requirements of product safety, electromagnetic compatibility detection and authentication. The cutting machine circuit board is designed into three parts, including a large control board, a main control small board and a high-frequency control board; the large control panel is provided with a plurality of electronic components and parts, wherein the electronic components and parts comprise an inverter main transformer, an IGBT tube group I, IGBT radiator I, CBB capacitor, an IGBT radiator II, a driving transformer, an electrolytic capacitor, a common mode inductor, a switching power supply transformer, an IGBT tube group II, a rectifier, a current transformer, an overheat protector, a main control panel, a high-frequency control panel, a rectifier tube I, an output filter reactor, a rectifier tube radiator I, a rectifier tube radiator II, a rectifier tube I and other electronic components, and the parts arranged on the large control panel comprise the main control panel and the high-frequency control panel; the main control platelet has many electronic components including PWM pulse width modulation integrated circuit chip, operational amplifier, resistor, capacitor, diode and voltage regulator tube; the high-frequency control panel is also provided with a plurality of electronic components and parts, including a high-voltage step-up transformer, a spark amplifier, a high-voltage ceramic chip capacitor, a relay, a resistor, a capacitor, a diode, a plug connector or a socket; the main control small plate is directly welded on the large control plate through a connecting piece; the high-frequency control board is connected with a circuit of the large control board part through a plug and a control line thereof; the small control panel circuit is mainly an output characteristic control circuit, and the core of the small control panel circuit is a circuit consisting of a UC3846 PWM chip and peripheral devices thereof. The whole control circuit mainly comprises an input filter circuit, an electrifying buffer circuit, an inverter main circuit, an output filter circuit, a switching power supply circuit, an IGBT drive circuit, a current detection and rectification conversion circuit, a thermal protection detection and control circuit, a current setting circuit, an electromagnetic valve control circuit, an arc striking control circuit, an output characteristic control circuit, a current display circuit, a high-frequency cut-off control circuit and the like. From the function of the circuit, the circuit mainly completes the work of input filtering, power-on buffering, rectification, filtering, inversion, output filtering, anti-interference, generation of various direct current working power supplies, PWM pulse width regulation, IGBT tube driving control, negative feedback control of inverter circuit output parameters (current) of the air plasma cutting process method and the like. The invention adopts a new technical scheme of anti-interference measures of control, hardware and software, and better solves the problems of high electromagnetic compatibility and reliability of the cutting machine. Finally, under the action of a control circuit, the air plasma cutting process method is realized, and the requirements of safety performance detection, authentication and the like are met.

The cutting machine has good electromagnetic compatibility, control performance, safety and reliability, so the cutting machine has better market adaptability. The good circuit and the structural design thereof are also the advantages of the invention and are the important guarantee of high efficiency, low cost production, high reliability and advanced manufacturing technology. The circuit principle, the circuit board and the whole structure of the cutting machine are designed with own unique features. The invention is protected by the patent application and aims to protect the circuit and the structural design of the cutting machine.

Disclosure of Invention

The invention relates to an inversion air plasma cutting machine with high electromagnetic compatibility and reliability, wherein a power supply of the cutting machine is single-phase 220-240V, the inversion air plasma cutting machine has the function of an air plasma cutting process method, and meets the requirements of product safety, electromagnetic compatibility detection and authentication.

The invention relates to a shell part of an air plasma cutting machine, which comprises a handle or a combined handle, a shell bottom plate, a front panel, a rear panel, a metal plate of a control panel, an output connecting plate and a shell screw.

The invention relates to a front panel of an air plasma cutting machine, which is provided with parts and components, wherein the parts and components mainly comprise a front panel, a metal plate of a control panel, an output connecting plate, a negative cutting gun gas-electricity integrated joint component connected with a cutting gun, a positive output quick joint component, an aviation socket plastic isolation plate, an aviation socket, a power supply indicator lamp (white), an overheating protection state indicator lamp (yellow), an output current regulation potentiometer and a knob thereof; the positive polarity output quick connector assembly is connected with the workpiece clamp cable and the workpiece; during cutting, the cutting gun gas-electricity integrated joint assembly with the negative polarity is connected with the cutting gun cable. The power indicator (white) indicates that the power is on. The overheat protection state indicator lamp (yellow) indicates whether an overheat state occurs. When the temperature of the internal device is too high and exceeds the action temperature, the indicator light can be lightened under the action of the control circuit; on the other hand, the air plasma cutter may be caused to stop the current output. In the case of a non-output of the cutter, the cooling effect of the fan will lower the temperature of the device. When the action temperature is recovered, the overheating phenomenon of the cutting machine is eliminated, the overheating indicator lamp is turned off, and meanwhile, the air plasma cutting machine can cut again. Of course, according to the requirement of product manufacture, the front panel can also be provided with components such as an ammeter, a voltmeter and the like so as to expand the functions of the product.

The invention relates to a back panel of an air plasma cutting machine, which is provided with parts and components mainly comprising a power switch, an electromagnetic valve, an air filter, a power supply wire and a plug, a power wire pull-off (also called a wire fixing device), a back outer plastic panel and a cooling fan. The power line and the plug are connected to a power supply grid. The power switch controls the on or off of the power supply of the cutting machine. The cooling fan is positioned at the rear part of the cutting machine, and cold air is fed from an air inlet hole at the rear part of the cutting machine. Some heating devices or parts of the circuit part, such as IGBT and radiator, fast recovery diode and radiator, can be cooled well. The design of the air duct and the cooling mode is beneficial to ensuring the working reliability of the circuit of the cutting machine and is one of the important reasons for realizing larger current and high load duration rate of the cutting machine.

The circuit board of the air plasma cutting machine is designed into three parts, including a large control board, a main control small board and a high-frequency control board; the large control panel is provided with a plurality of electronic components and parts, and comprises an inverter main transformer, an IGBT tube group I, IGBT radiator I, CBB capacitor, an IGBT radiator II, a driving transformer, an electrolytic capacitor, a common mode inductor, a switching power supply transformer, an IGBT tube group II, a rectifier, a current transformer, an overheat protector, a main control small plate, a high-frequency control panel, a rectifier tube I, an output filter reactor, a rectifier tube radiator I, a rectifier tube radiator II, a rectifier tube I and other electronic components; the parts arranged on the large control panel comprise a main control small plate and a high-frequency control panel; the main control platelet has many electronic components including PWM pulse width modulation integrated circuit chip, operational amplifier, resistor, capacitor, diode and voltage regulator tube; the high-frequency control panel is also provided with a plurality of electronic components and parts, including a high-voltage step-up transformer, a spark amplifier, a high-voltage ceramic chip capacitor, a relay, a resistor, a capacitor, a diode, a plug connector or a socket; the main control small plate is directly welded on the large control plate through a connecting piece; the high-frequency control board is connected with the circuit of the large control board part through a plug and a control line thereof.

The large control board is vertically installed on the bottom board of the machine shell, the main control small board is welded on the large control board, the high-frequency control board is installed on the large control board, and a sufficient creepage distance is reserved between the high-frequency control board and the main control small board, so that a control circuit part of the cutting machine is equivalently surrounded by a metal shell consisting of the shell, the bottom board, the rear panel and the front panel. The small control board circuit is mainly an output characteristic control circuit. The core of the pulse width modulation circuit is a circuit composed of a UC3846 PWM chip and peripheral devices thereof. The whole control circuit mainly comprises an input filter circuit, an electrifying buffer circuit, an inverter main circuit, an output filter circuit, a switching power supply circuit, an IGBT drive circuit, a current detection and rectification conversion circuit, a thermal protection detection and control circuit, a current setting circuit, an electromagnetic valve control circuit, an arc striking control circuit, an output characteristic control circuit, a current display circuit, a high-frequency cut-off control circuit and the like. From the function of the circuit, the circuit mainly completes the work of input filtering, power-on buffering, rectification, filtering, inversion, output filtering, anti-interference, generation of various direct current working power supplies, PWM pulse width regulation, IGBT tube driving control, negative feedback control of inverter circuit output parameters (current) of the air plasma cutting process method and the like. The invention adopts a new technical scheme of anti-interference measures of control, hardware and software, and better solves the problems of high electromagnetic compatibility and reliability of the cutting machine. Finally, under the action of a control circuit, the air plasma cutting process method is realized, and the requirements of safety performance detection, authentication and the like are met.

The anti-interference measures of the hardware circuit of the cutting machine mainly comprise the following aspects:

1) and input to a filter circuit. The input filter circuit consists of 7MT1, 7MT2 common mode inductors, 7R1 resistors and 7C 3-7C 7 capacitors, the 7C7 capacitors are connected in parallel at two ends of the rear stage of a power switch S1 of the cutting machine, the 7MT1 common mode inductors are connected at the rear stage of the 7MT1 common mode inductors, the 7R1 resistors and the 7C5 capacitors are connected in parallel at the rear stage of the 7MT1 common mode inductors, one ends of the 7MT1 common mode inductors are connected with the 7C3 capacitors, the other ends of the 7MT1 common mode inductors are connected with the 7C4 capacitors, and the other ends of the 7C3 capacitors and the 7C4 capacitors are connected to a PE end (frame) or a protective grounding end of the cutting machine; the post-stage of the 7MT1 common mode inductor is connected with a 7MT2 common mode inductor, and the post-stage of the 7MT2 common mode inductor is connected with a 7C6 capacitor and the input end of a chopper rectifier BD1 in parallel. The input filter circuit can prevent interference signals from a power grid from entering a control circuit of the cutting machine on one hand, and can reduce interference signals generated by the cutting machine to enter the power grid on the other hand. The arrangement of the input filter circuit is one of important preconditions for ensuring that the cutting machine can pass EMC electromagnetic compatibility authentication, and is also one of important measures for resisting interference of a hardware circuit and improving the reliability of the cutting machine.

2) And an output filter circuit. An output filter circuit in the main circuit of the cutting machine consists of an output current filter inductor LX, resistors 9R 1-9R 6, filter capacitors 9C 1-9C 6, voltage dependent resistors 9VR2 and 9VR3, and diodes 9Z 1-9Z 3; 9R1 is connected in series with 9C1 and then connected in parallel across the output rectifying fast recovery diode 9D1, similarly 9R2 is connected in series with 9C2 and then connected in parallel across the output rectifying fast recovery diode D6; 9R3 is connected with 9C3 in series and then connected with two ends of an output rectifying fast recovery diode 9D3 in parallel; the 9R4 and the 9C4 are connected in series and then connected in parallel at two ends of an output rectifying fast recovery diode D8; the full-wave rectifying circuit is composed of D6, D8, 9D1 and 9D3, and the input end of the full-wave rectifying circuit is connected in parallel with two ends of a secondary output winding of the inverter main transformer T11; 9R5 is connected in parallel with the two ends of the output of the full-wave rectification circuit; the negative end of the full-wave rectification circuit is connected with an LX filter inductor, and a series circuit consisting of a 9R6 resistor, a 9C5 capacitor, a plug 9CN1, diodes 9Z 1-9Z 3 and a 9VR2 is connected in parallel between the other end of the LX filter inductor and the output positive polarity end of the full-wave rectification circuit; the series circuit is characterized in that: three positive polarity of 9Z 1-9Z 3 are connected in series, the anode end of 9Z1 is connected with the output positive polarity end of the full-wave rectification circuit, the cathode end of 9Z3 is connected with 9VR2, and 9VR2 is connected with the LX filter inductor and one end of an output high-frequency coupling transformer T2; the other end of the T2 is connected with a negative output end; the positive output terminal of the full-wave rectification circuit is also connected to the positive output terminal, and at the same time, one terminals of 9VR3 and 9C6 are also connected, and the other terminals of 9VR3 and 9C6 are connected to the PE terminal or protective ground terminal (frame) of the cutter. The output filter circuit can inhibit current fluctuation, reduce burr abrupt change signals in current waveforms, reduce spike interference signals in the rectification process of the fast recovery diode, simultaneously protect the fast recovery diodes D6, D8, 9D1 and 9D3, and prevent interference signals from the output end of the cutting machine from entering a control circuit of the cutting machine, so that the reliability of the cutting machine is improved.

3) Anti-interference measures of an IGBT switch and an inverter circuit; the input stage part of the IGBT inverter full-bridge circuit, namely the two ends of A, B are connected in parallel with C85 and C86 anti-interference CBB capacitors; in the working process of the inverter main circuit, a peak interference signal can be generated in the on-off control process of the IGBT switching device. The interference signals are reduced or controlled by an anti-interference circuit connected with resistors and capacitors (such as R81, C21-1; R82, C22-1; R83, C23-1; R84, C24-1) at two ends of the IGBT device in parallel.

4) Anti-interference measures of the direct-current power supply voltage; c59 and C60 anti-interference capacitors are arranged between the input end of the +310V power supply leading-in switching power supply circuit and a rack or protective grounding; filter capacitors, such as C4, C12 and C18 capacitors, are arranged at the input end of a power supply circuit generating +5V, +15V and-15V; between the output of the +5V, +15V, -15V power supply and the ground, a filter capacitor, such as C2, C30, C30-1, is arranged; decoupling capacitors, such as C16, C17, C31 and C32, are provided between the operational amplifier +15V, -15V power supply to ground and the +15V power supply to ground of the PWM chip.

5) And (4) anti-interference measures for driving the IGBT. Such as anti-interference capacitors of C29, C69, C41, C42, C44 and C47, and a filter circuit of a pi type consisting of electrolytic capacitors of C6 and C45 and R58.

6) Anti-interference measures of a cutting gun switch; the LED driving circuit comprises a cutting gun switch, one end of the cutting gun switch is connected with a filter inductor L1, the other end of the cutting gun switch is connected with a filter inductor L2, the other end of a filter inductor L2 is connected with a cathode of a D26, a C18, an anode of an electrolytic capacitor C20, an R18 resistor and a C11, an anode of the D26 is connected with a synonym end of a secondary independent winding of a switching power supply transformer T4, the other end of the filter inductor L1 is connected with a cathode of a R11 diode, a C13 diode, a cathode of a D3 diode and the other end of a C11 diode, the other end of the R11 is connected with an anode of a light emitting diode in an optical coupler U11, and cathodes of the light emitting diodes in the optical coupler U11, the other ends of the C13, the C18 and the R18 and a cathode of the electrolytic capacitor C20 are connected with a synonym end of the secondary independent winding of the switching power supply transformer T4. When the cutting gun switch S is closed, the light emitting diode in the optocoupler U11 can emit light, and an output stage triode in the optocoupler is conducted to finally control other circuits of the cutting machine. Because the cutting torch switch line is longer, simultaneously, has the wire of heavy current in the cutting torch cable to also there is the wire that high frequency high-voltage signal passes through the cutting torch during the striking, consequently, can bring the interference to the switch control line of cutting torch, set up above-mentioned cutting torch switch line anti-jamming circuit, its effect is exactly utilizing the circuit of filter capacitor, filter inductance, opto-coupler etc. constitution, reduces the interference that comes from cutting torch switch control line, ensures cutting torch control circuit's reliable work.

In addition, in terms of structural design, there are also measures for electromagnetic shielding; the large control board is vertically arranged on the bottom board of the machine shell, the main control small board is welded on the large control board, and the high-frequency control board is arranged on the large control board and has enough creepage distance with the main control small board and the large control board. The control circuit part of the cutting machine is equivalently surrounded by a metal shell consisting of a shell, a bottom plate, a back panel and a front panel. The electromagnetic interference shielding device can play roles in isolating strong electromagnetic interference, limiting electromagnetic radiation and the like.

The measures are one of the important prerequisites for ensuring the working reliability of the air plasma cutting machine product manufactured by the circuit of the invention.

For the air plasma cutting machine with different current grades and load duration requirements, products with different output rated currents and load duration can be formed by adjusting the number of a small number of parts and specification parameters on the circuit board, so that the products are serialized. For example, the number of large electrolytic capacitors is changed; changing parameters of a rectifier bridge; changing the current grade and the size of a radiator of the IGBT device; changing the model and parameters of the fast recovery diode; the specifications, parameters and the like of the inverter main transformer and the output filter reactor are changed, and series products with different specifications can be easily formed. Such as products of various current grades and specifications, such as 20A/88V, 30A/92V, 40A/96V and the like. These variations, of course, aim to match the production costs of the product with the specifications and performance specifications of the respective machine. In this way, optimal cost control can only be achieved for each size of cutter. This enhances the market competitiveness of the developed product.

The air plasma cutting machine has good electromagnetic compatibility, control performance, safety and reliability, so the cutting machine has better market adaptability. The good circuit and the structural design thereof are also the advantages of the invention and are the important guarantee of high-efficiency and low-cost production, high electromagnetic compatibility and reliability and advanced manufacturing technology. The invention has unique design of the circuit principle, the circuit board and the whole machine structure of the air plasma cutting machine. The invention is directed to protecting the circuit and structure design of the air plasma cutting machine.

Drawings

FIG. 1 is a schematic diagram of an exemplary air plasma cutter made using the present invention;

FIG. 2 is a schematic circuit diagram of the air plasma cutter of the present invention;

FIG. 3 is a schematic view of a large control panel assembly;

the names of the components in the drawings are as follows: 1. a handle; 2. a housing; 3. a large control panel assembly; 4. an electromagnetic gas valve; 5. a rear plastic panel; 6. the power line is not pulled off; 7. a power input line; 8. a power switch; 9. an air cleaner; 10. a cooling fan; 11. a chassis base plate; 12. a front plastic panel; 13. an output connection plate; 14. a positive polarity output quick connector assembly; 15. an aviation socket plastic spacer; 16. an aviation socket; 17. the cutting gun gas-electricity integrated connector assembly; 18. a metal plate of the control panel; 19. a current regulation potentiometer and a knob thereof; 20. an overheat indicator light; 21. a power indicator light; 22. an inverting main transformer; 23. an IGBT tube group I; 24. an IGBT radiator I; 25. a CBB capacitor; 26. an IGBT radiator II; 27. a drive transformer; 28. an electrolytic capacitor; 29. a common mode inductor; 30. a switching power supply transformer; 31. an IGBT tube group II; 32. a rectifier bridge or rectifier; 33. a current transformer; 34. an overheat protector; 35. a master control platelet; 36. a high-frequency control board; 37. a rectifier tube I; 38. an output filter reactor; 39. a rectifier tube radiator I; 40. a rectifier tube radiator II; 41. a rectifier tube II; 42. a work holder and its cable; 43. an aviation plug of a cutting gun switch; 44. a cutting gun sheath; 45. a cutting gun.

Detailed Description

As shown in fig. 1, the structure of the IGBT inverter air plasma cutting machine manufactured by the present invention is schematically illustrated and its parts are listed. The main components of the device comprise:

1) the shell part comprises a handle or a combined handle 1, a shell 2, a shell bottom plate 11, a front plate 12, a rear plate 5, a metal plate 18 of a control panel, an output connecting plate 13 and a shell screw.

2) The components mounted on the back panel mainly comprise a power switch 8, an electromagnetic valve 4, an air cleaner 9, a power supply wire and a plug 7, a power wire pull-off (also called a wire fixing device) 6, a back outer plastic panel 5 and a cooling fan 10. The power cord and plug 7 are connected to the power supply grid. The power switch 8 controls the on or off of the power supply of the cutting machine. The cooling fan 10 is located at the rear of the cutting machine, and cold air is supplied from an air inlet hole at the rear of the cutting machine. Some heating devices or parts of the circuit part, such as IGBT and radiator, fast recovery diode and radiator, can be cooled well. The design of the air duct and the cooling mode is beneficial to ensuring the working reliability of the circuit of the cutting machine and is one of the important reasons for realizing larger current and high load duration rate of the cutting machine.

3) The front panel is mainly provided with a front panel 12, a metal plate 18 of a control panel, an output connecting plate 13, a negative cutting gun gas-electricity integrated joint component 17 connected with a cutting gun, a positive output quick joint component 14, an aviation socket plastic isolation plate 15, an aviation socket 16, a power supply indicator lamp (white) 21, an overheating protection state indicator lamp (yellow) 20, an output current regulation potentiometer and a knob 19 thereof, wherein the cutting gun is provided with a sheath 44, and a switch aviation plug 43 of the cutting gun is connected with the aviation socket 16; the positive polarity output quick connector assembly 14 connects the workpiece clamp cable and the workpiece; during cutting, the cutting gun gas-electricity integrated connector assembly 17 with the negative polarity is connected with a cutting gun cable. A power indicator lamp (white) 21 indicates power-on. The overheat protection state indicator lamp (yellow) 20 indicates whether an overheat state occurs. When the temperature of the internal device is too high and exceeds the action temperature, the indicator light can be lightened under the action of the control circuit; on the other hand, the air plasma cutter may be caused to stop the current output. In the case of a non-output of the cutter, the cooling effect of the fan will lower the temperature of the device. When the action temperature is recovered, the overheating phenomenon of the cutting machine is eliminated, the overheating indicator lamp is turned off, and meanwhile, the air plasma cutting machine can cut again. Of course, according to the requirement of product manufacture, the front panel can also be provided with components such as an ammeter, a voltmeter and the like so as to expand the functions of the product.

4) A control board section including a large control board 3, a main control small board 35, and a high-frequency control board 36; the large control panel 3 has many electronic components and parts, including an inverter main transformer 22, an IGBT tube group I23, an IGBT radiator I24, a CBB capacitor 25, an IGBT radiator II 26, a driving transformer 27, an electrolytic capacitor 28, a common mode inductor 29, a switching power supply transformer 30, an IGBT tube group II 31, a rectifier 32, a current transformer 33, an overheat protector 34, a main control board 35, a high-frequency control panel 36, a rectifier tube I37, an output filter reactor 38, a rectifier tube radiator I39, a rectifier tube radiator II 40, a rectifier tube I41, and other electronic components; the parts mounted on the large control panel 3 include a main control panel 35 and a high-frequency control panel 36; the main control board 35 has many electronic components including a PWM pulse width modulation integrated circuit chip, an operational amplifier, a resistor, a capacitor, a diode, and a voltage regulator tube; the high-frequency control board 36 also has many electronic components and parts, including a high-voltage step-up transformer, a spark amplifier, a high-voltage ceramic capacitor, a relay, a resistor, a capacitor, a diode, a plug connector or a socket; the main control small plate 35 is directly welded on the large control plate 3 through a connecting piece; the high-frequency control board 36 is connected with the circuit of the large control board 3 part through a plug and a control line thereof. The large control board 3 of the invention is vertically installed on the chassis bottom plate 11, the main control small board 35 is welded on the large control board 3, the high-frequency control board 36 is installed on the large control board 3, and a sufficient creepage distance is left between the main control small board 35 and the large control board 3. The control circuit part of the cutting machine is equivalently surrounded by a metal shell consisting of a shell 2, a bottom plate 11, a back panel and a front panel.

The circuit board control part is electrically connected with components on the front panel and the rear panel of the air plasma cutting machine, such as a current adjusting potentiometer 19, a fan 10, indicator lamps 20 and 21, a power switch 8, an electromagnetic air valve 4 and the like, through control wires. The circuit boards, devices or parts are connected together according to the circuit schematic diagram of the air plasma cutting machine. The control of the circuit output characteristics of the air plasma cutting method can be met.

Fig. 2 is a schematic circuit diagram of the air plasma cutter of the present invention. As shown in fig. 2, an interface is provided between the large control board 3, the main control board 35, and the high-frequency control board 36. The three control circuit boards are connected together according to the corresponding interface identification and the circuit schematic diagram. The main control small board 3 is directly welded on the large control board 3 through a connector AA, and the two circuit boards are connected without adopting a connecting wire.

As shown in fig. 2, the whole control circuit mainly comprises an input filter circuit, an electrifying buffer circuit, an inverter main circuit, an output filter circuit, a switching power supply circuit, an IGBT driving circuit, a current detection and rectification conversion circuit, a thermal protection detection and control circuit, a current setting circuit, an electromagnetic valve control circuit, an arc striking control circuit, an output characteristic control circuit, a current display circuit, a high-frequency cut-off control circuit and other functional circuits. Finally, under the action of the control circuit, the air plasma cutting process is realized, and the requirements of electromagnetic compatibility, safety performance detection, authentication and the like are met. The invention adopts a new technical scheme of anti-interference measures of control, hardware and software, and better solves the problems of high electromagnetic compatibility and reliability of the cutting machine. Some description of the related functional circuitry follows:

referring to the attached figure 2, the inverter main circuit comprises a power switch S1, a power-on buffer circuit, an input filter circuit, an input rectifier bridge BD1, a power-on buffer circuit consisting of a 3PTC1 thermistor, a JR1 relay and a control circuit thereof, a filter circuit consisting of C60-1, C60-2, C60-3 large electrolytic capacitors (470 mu F/400V and the like), IGBT 1-IGBT 4 IGBT tubes, a T11 inverter main transformer, 9D1, 9D3, D6, D8 fast recovery diodes and an output filter circuit. The cutting current and voltage are output from the OUT (+) positive and OUT (-) negative output terminals.

Referring to FIG. 2, the terminals L and N are connected to a 220V-240V/50Hz power supply. After the power switch S1 is turned on, the air plasma cutter is powered on. A white power indicator light on its front panel lights up. Alternating current from a power grid is rectified into pulsating direct current through an input filter circuit, a power-on buffer circuit and a rectifier BD 1. The rectified output firstly passes through a power-on buffer circuit consisting of a 3PTC1 thermistor and a JR1 relay, then large electrolytic capacitors of C60-1, C60-2 and C60-3 are charged, the voltage is gradually increased, and finally the voltage is changed into more stable direct current of +310V, and the direct current is output to a post-stage circuit from A, B.

Referring to fig. 2, the input filter circuit is composed of 7MT1, 7MT2 common mode inductors, 7R1 resistors and 7C 3-7C 7 capacitors, the 7C7 capacitors are connected in parallel to the two ends of the rear stage of the power switch S1 of the cutting machine, the 7MT1 common mode inductors are connected to the rear stage of the 7MT1 common mode inductors, the 7R1 resistors and the 7C5 capacitors are connected in parallel to the rear stage of the 7MT1 common mode inductors, one end of the 7MT1 common mode inductors is connected with the 7C3 capacitors, the other end of the 7MT1 common mode inductors is connected with the 7C4 capacitors, and the other ends of the 7C3 capacitors and the 7C4 capacitors are connected to a PE terminal (rack) or a protective grounding terminal of the cutting machine; the post-stage of the 7MT1 common mode inductor is connected with a 7MT2 common mode inductor, and the post-stage of the 7MT2 common mode inductor is connected with a 7C6 capacitor and the input end of a chopper rectifier BD1 in parallel. The arrangement of the input filter circuit is one of important preconditions for ensuring that the cutting machine can pass EMC electromagnetic compatibility certification.

For the power-on buffer circuit, the JR1 relay is switched on when the power switch S1 is switched on, and acts after a certain delay time, the contact of the relay is closed, and the 3PTC1 thermistor is short-circuited. The delay of the JR1 relay is realized by the control circuit. The charging of the large electrolytic capacitors of C60-1, C60-2 and C60-3 firstly passes through the thermistor of 3PTC1 and then is short-circuited with the thermistor of 3PTC 1. Such a control circuit is referred to as a power-up buffer circuit.

Referring to FIG. 2, the large electrolytic capacitors of C60-1, C60-2 and C60-3 play a role in filtering. A. The +310V direct current output between B is supplied to a full-bridge inverter main circuit which is composed of IGBT tubes 1-IGBT 4, a T11 inverter main transformer, 9D1, 9D3, D6 and D8 fast recovery diodes, an output filter circuit and the like, and the full-bridge inverter main circuit mainly has the functions of: the high voltage dc is converted to an intermediate frequency (tens of KHz) ac. The T11 inverter transformer realizes voltage reduction and conversion of large current output. The 9D1, 9D3, D6 and D8 fast recovery diodes convert the medium-frequency alternating current output by the inverter transformer into direct current. Because the converted current waveform is pulsating and unstable, which is not beneficial to the stability of the cutting process, the current filter reactor LX and the output filter circuit are adopted for filtering. Therefore, the output current waveform becomes stable, the interference signal can be prevented from damaging the device and the reliable work of the circuit, and the high-quality cutting seam can be obtained and the reliability of the cutting machine can be guaranteed.

Referring to the attached figure 2, an output filter circuit in a main circuit of the cutting machine consists of an output current filter inductor LX, resistors 9R 1-9R 6, filter capacitors 9C 1-9C 6, voltage dependent resistors 9VR2 and 9VR3, and diodes 9Z 1-9Z 3; 9R1 is connected in series with 9C1 and then connected in parallel across the output rectifying fast recovery diode 9D1, similarly 9R2 is connected in series with 9C2 and then connected in parallel across the output rectifying fast recovery diode D6; 9R3 is connected with 9C3 in series and then connected with two ends of an output rectifying fast recovery diode 9D3 in parallel; the 9R4 and the 9C4 are connected in series and then connected in parallel at two ends of an output rectifying fast recovery diode D8; the full-wave rectifying circuit is composed of D6, D8, 9D1 and 9D3, and the input end of the full-wave rectifying circuit is connected in parallel with two ends of a secondary output winding of the inverter main transformer T11; 9R5 is connected in parallel with the two ends of the output of the full-wave rectification circuit; the negative end of the full-wave rectification circuit is connected with an LX filter inductor, and a series circuit consisting of a 9R6 resistor, a 9C5 capacitor, a plug 9CN1, diodes 9Z 1-9Z 3 and a 9VR2 is connected in parallel between the other end of the LX filter inductor and the output positive polarity end of the full-wave rectification circuit; the series circuit is characterized in that: three positive polarity of 9Z 1-9Z 3 are connected in series, the anode end of 9Z1 is connected with the output positive polarity end of the full-wave rectification circuit, the cathode end of 9Z3 is connected with 9VR2, and 9VR2 is connected with the LX filter inductor and one end of an output high-frequency coupling transformer T2; the other end of the T2 is connected with a negative output end; the output positive polarity end of the full-wave rectification circuit is also connected to the positive output end, meanwhile, one ends of 9VR3 and 9C6 are also connected, and the other ends of 9VR3 and 9C6 are connected to the PE end or protective grounding end (frame) of the cutting machine; the primary M, N terminal of the output high-frequency coupling transformer T2 is connected to the 2CN2 plug of the high-frequency arc striking circuit board, which is also the M, N terminal of the high-frequency arc striking circuit board, through a connecting wire.

Referring to fig. 2, the +310V dc power output from A, B is also supplied to the switching power supply circuit for operation. The switching power supply circuit consists of a switching power supply transformer T4, optical couplers U11 and U28, a switching power supply PWM (pulse width modulation) control chip U30 (UC 3845B), U29 field effect transistors, 7805, 7815 and 7915 integrated voltage regulators, and devices around the switching power supply transformer, the U30, the U29 field effect transistors, the 7805, the 7815 and the 7915 integrated voltage regulators and the like, and has the functions of generating +5V, +15V, +24V and-15V power supply voltages and supplying the voltages to corresponding control circuits for live working. For the switching power supply circuit part, a switching power supply control chip U30 (UC 3845B) and a primary winding of a switching power supply transformer T4, and a circuit formed by a voltage regulator tube, a diode, a resistor, a capacitor and the like around the switching power supply control chip U30 and the primary winding belong to a +310V high-voltage loop. In order to ensure the safety of the control circuit, in fig. 2, isolation is performed by using U11 and U28 photocouplers. In the switching power supply circuit part, the purpose is to obtain +5V, +15V, +24V, -15V power supply voltage, and supply the power supply voltage for different devices and circuits. Referring to fig. 2, in the input part and the high-voltage side circuit part of the switching power supply circuit, filter capacitors C59 and C60 are connected in parallel between the two ends a and B of the dc bus voltage +310V to the rack or the protective ground, the end a is connected with the capacitors C57 and C60, the resistors R76 and R77, the dotted end (the end with "●") of the main primary winding of the switching power supply transformer T4, the capacitor C57 and the resistor R76 are connected in parallel, the other end is connected with the cathode of the diode D30, the anode of D30 and the dotted end (the end without "●") of the main primary winding of the switching power supply transformer T4 are connected with the D end of the fet U29, and the other end of the resistor R77 is connected with the pin 7 of the PWM chip U30 (UC 3845B); the C56 capacitor and the R79 resistor are connected in parallel, one end of the C56 capacitor is connected with the B end, the B end is also the ground end of the input high-voltage part of the switching power supply circuit, and the other end of the C56 capacitor is connected to the pin 7 of the U30 PWM chip; the S end of the field effect transistor U29 is connected with a resistor R71 and a resistor R72, the other end of the resistor R71 is connected with the ground end of the input high-voltage part, the other end of the resistor R72 is connected with a pin 3 of a U30 PWM chip, and a C53 capacitor is connected in parallel between the pin 3 of the U30 PWM chip and the ground end of the input high-voltage part; a C54 capacitor is connected in parallel between the 4 pins of the U30 PWM chip and the ground end of the input high-voltage part; a C55 capacitor is connected in parallel between the 8 pins of the U30 PWM chip and the ground end of the input high-voltage part; a resistor R73 is connected between the 8 pins of the U30 PWM chip and the 4 pins; the 5 pin of the U30 PWM chip is connected with the ground end of the input high-voltage part; the 6 pin of the U30 PWM chip is connected with the R74 resistor, and the other end of R74 is connected with the G end of the field effect tube U29; a C51 capacitor and an R75 resistor which are connected in parallel are connected between pins 1 and 2 of the U30 PWM chip; a pin 2 of the U30 PWM chip is connected with an R69 resistor, the other end of R69 is connected with an R68 and an emitter of an output stage triode in an optocoupler U28, and the other end of R68 is connected with the ground end of an input high-voltage part; the collector of an output triode in an optocoupler U28 is connected with a pin 7 of a U30 PWM chip and an R70 resistor, the other end of the R70 is connected with the anode of a C52 electrolytic capacitor and the cathode of a D29 diode, the cathode of a C52 electrolytic capacitor is connected with the ground end of an input high-voltage part, the anode of the D29 diode is connected with the synonym end (the end without '●') of an auxiliary winding of a switching power supply transformer T4, and the homonymy end (the end with '●') of the auxiliary winding of the switching power supply transformer T4 is connected with the ground end of the input high-voltage part; in the output part and the low-voltage side circuit part of the switching power supply circuit, the secondary side of the switching power supply transformer T4 has two windings, one is an independent secondary winding, and the other is a secondary winding with a center tap; for the secondary winding with a center tap, two windings are connected in series in positive polarity, that is, the different-name end (the end without "●") of one winding is connected with the same-name end (the end with "●") of the other winding, which is also called a common connection point, the connection point is also the ground end of +5V, +15V, +24V, -15V power voltage, the connection ground end divides the two windings into an upper winding and a lower winding, the same-name end (the end with "●") of the upper winding is connected with the cathode of a D27 diode, the anode of D27 is connected with the common connection point or the ground in parallel and connected with a C4 capacitor and a C48 electrolytic capacitor, the anode of the C48 electrolytic capacitor is connected with the ground end, the anode of D27 is connected with the input end of the 7915 integrated voltage regulator, the ground end of the 7915 integrated voltage regulator is connected with the common connection point or the ground, the output-15V of the 7915 integrated voltage regulator is connected with a C2 capacitor and a C7 electrolytic capacitor in parallel, the positive electrode of the C7 electrolytic capacitor is connected with the ground terminal; the synonym end (the end without ●) of the lower winding is connected with the anode of a U27 diode, a C12 capacitor and a C21 electrolytic capacitor are connected in parallel between the cathode of U27 and a common connection point or the ground, the cathode of a C21 electrolytic capacitor is connected with the ground, the anode of U27 is connected with the input end of the 7815 integrated voltage stabilizer, the ground end of the 7815 integrated voltage stabilizer is connected with the common connection point or the ground, a C30 capacitor and a C19 electrolytic capacitor are connected in parallel between the output +15V of the 7815 integrated voltage stabilizer and the ground, and the cathode of a C19 electrolytic capacitor is connected with the ground; the anode of the U27 outputs +24V to the ground, and the +24V power supply supplies power to the cooling Fan Fan and the relay JR1 to work; the anode of U27 is connected with the cathode of a voltage regulator tube Z5, the anode of Z5 is connected with a resistor R67, the other end of the resistor R67 is connected with the anode of an input-stage light-emitting diode in an optocoupler U28, the cathode of the input-stage light-emitting diode in the optocoupler U28 is grounded, and a capacitor C50 is connected between the anode of the input-stage light-emitting diode in U28 and the ground; for the independent secondary winding and the output power circuit part thereof, power is mainly supplied to a cutting gun switch control circuit, in the attached drawing 2, S is a cutting gun switch which is arranged on the cutting gun, two control wires of the switch are connected to a two-core aviation plug, the plug is connected to a two-core aviation socket below the front panel of the cutting machine, and the plug is connected to the output part in the switch power circuit through a connecting wire of the socket. One end of a cutting gun switch S is connected with a filter inductor L1, the other end of the cutting gun switch S is connected with a filter inductor L2, the other end of a filter inductor L2 is connected with a cathode of a D26, a C18, an anode of an electrolytic capacitor C20, an R18 resistor and a C11, an anode of the D26 is connected with a synonym end (one end without '●') of a secondary independent winding of a switching power supply transformer T4, the other end of a filter inductor L1 is connected with a cathode of a R11, a C13 diode, a cathode of a D3 diode and the other end of a C11, the other end of the R11 is connected with an anode of a light emitting diode in an optical coupler U11, and a cathode of the light emitting diode in the optical coupler U11, the other ends of the C13, the C18 and the R18 and a cathode of the electrolytic capacitor C20 are connected with a synonym end (one end with the '●') of a secondary independent winding of the switching power supply transformer T4. When the cutting gun switch S is closed, the light emitting diode in the optocoupler U11 can emit light, and an output stage triode in the optocoupler is conducted to finally control other circuits of the cutting machine. Because the cutting torch switch line is longer, simultaneously, has the wire of heavy current in the cutting torch cable to also there is the wire that high frequency high-voltage signal passes through the cutting torch during the striking, consequently, can bring the interference to the switch control line of cutting torch, set up above-mentioned cutting torch switch line anti-jamming circuit, its effect is exactly utilizing the circuit of filter capacitor, filter inductance, opto-coupler etc. constitution, reduces the interference that comes from cutting torch switch control line, ensures cutting torch control circuit's reliable work.

When the input power supply voltage of the cutting machine changes between 100V-270V, the U29 field effect tube is in an on-end control state under the control action of the U30 PWM chip, so that the power supply voltages of +5V, +15V, +24V, -15V and the like can be obtained at the secondary output rectifying circuit part of the T4 switching transformer, the normal work of each control circuit of the cutting machine can be ensured, the air plasma cutting machine can work in a large power grid voltage fluctuation range, and the better power grid voltage fluctuation resistance is achieved.

The operation principle of this part of the switching power supply is described briefly above. Much knowledge of the switching power supply is involved if it is necessary to know the detailed operation of this circuit part. The reader can inquire the relevant switching circuit books or data for further understanding. And will not be described in detail herein.

It can be seen from the circuit and principle of the switching power supply part that the present invention does not use a general control transformer and related voltage conversion circuit to generate the above-mentioned several dc power supply voltages. The circuit takes +310V from the main loop. The size, the dimension and the weight of the switch transformer are far smaller than those of a common control transformer, so that the cost of the air plasma cutting machine is reduced, and the technical additional value of the air plasma cutting machine is improved.

An IGBT driving circuit part, as shown in figure 2, comprises driving transformers T3, Q6, a U23P channel field effect transistor (IRF 9Z 24N), a U24, a Q8N channel field effect transistor (IRFZ 24N), D601-D604 fast diodes, and resistors, capacitors and the like at the periphery of the driving transformers; the inverter circuit part has 4 IGBTs, so 4-way IGBT driving is provided, and the driving circuit form of each part is consistent. The partial circuit inputs control signals AA5 and AA7 from the output ends A OUT (AA 7 interface) and B OUT (AA 5 interface) of a PWM chip U2 (UC 3846) in an output characteristic control circuit on a main control board. Since the driving power of the signal output by the U2 chip is low, the signal needs to be amplified by a driving power circuit, and the working states of the 4 IGBTs are controlled by a driving transformer T3 and a peripheral driving circuit thereof. The control signals output by the U2 Pulse Width Modulation (PWM) chip are two sets of square wave pulse signals. The two groups of square-wave pulse signals have a fixed time difference in time, which is also known in the art as dead time. Is one of important parameters for ensuring the alternative work of the two groups of switches of the IGBT. The time is determined by the parameter settings of the peripheral devices (R21 and R22 at RT end and C7 and C8 at CT end) of the U2 chip. As to how to determine, the relevant usage data or description of UC3846 needs to be checked. And will not be repeated here. Here, it should be noted that: the PWM signal is a signal for determining the output voltage and current of the inversion main circuit of the air plasma cutting machine. And the PWM signal is determined by a current regulation given signal Ug and a current negative feedback signal Ufi of the air plasma cutting machine.

The IGBT driving circuit is divided into a low-voltage side driving circuit and a high-voltage side driving circuit, 4 IGBT driving circuits are arranged on the inverter circuit part, and the form of each high-voltage side driving circuit is consistent; the driving transformer T3 has 4 independent secondary windings, and the IGBT driving circuit is divided into a low-voltage side driving circuit and a high-voltage side driving circuit through T3; taking one of the high-voltage side driving circuits as an example, the circuit composition of the high-voltage side driving circuit is described, wherein the cathode of the D601 fast recovery diode is connected with an R601 resistor, the homonymous end (one end with '●') of one secondary winding of a driving transformer T3, the anode of the D601 is connected with an R605 resistor, the other end of the R605 connected with the R601 resistor is connected with the G1 gate of an IGBT1, the heteronymous end (one end without '●') of the secondary winding of the driving transformer T3 is connected with the E1 drain of an IGBT1, and a C601 capacitor is connected in parallel between the G1 and the E1 poles of the IGBT 1; similarly, the cathode of the D602 fast recovery diode is connected with the R602 resistor, the synonym terminal (one end without "●") of the other secondary winding of the driving transformer T3, the anode of the D602 is connected with the R606 resistor, the other end of the R606 resistor is connected with the G2 gate of the IGBT2, the synonym terminal (one end with "●") of the secondary winding of the driving transformer T3 is connected with the E2 drain of the IGBT2, and a C602 capacitor is connected in parallel between the G2 and E2 poles of the IGBT 2; the cathode of the D604 fast recovery diode is connected with the R604 resistor and the dotted terminal (one end with '●') of the other secondary winding of the driving transformer T3, the anode of the D604 is connected with the R608 resistor, the other end of the R608 resistor is connected with the G3 grid of the IGBT3, the different-dotted terminal (one end without '●') of the secondary winding of the driving transformer T3 is connected with the E3 drain of the IGBT3, and a C604 capacitor is connected between the G3 and E3 poles of the IGBT3 in parallel; the cathode of the D603 fast recovery diode is connected with the R603 resistor and the synonym terminal (one end without ●) of the other secondary winding of the driving transformer T3, the anode of the D603 is connected with the R607 resistor, the other end of the R607 is connected with the R603 resistor, the other end of the R603 resistor is connected with the G4 grid of the IGBT4, the synonym terminal (one end with ●) of the secondary winding of the driving transformer T3 is connected with the E4 drain of the IGBT4, and a C603 capacitor is connected between the G4 and the E4 poles of the IGBT4 in parallel.

The IGBT low-voltage side driving circuit consists of Q6 and U23P channel field effect transistors (IRF 9Z 24N), U24 and Q8N channel field effect transistors (IRFZ 24N), R58, R59, R60, R61, R62 and R63 resistors, C29, C69, C40, C41, C42, C44, C47 and C69 capacitors, C45 and C6 electrolytic capacitors and a primary winding of a driving transformer T3; the two ends of a C6 electrolytic capacitor are +15V power supplies, a C29 capacitor is connected between +15V and the ground in parallel, one end of an R58 is connected with +15V, the other end of an R58 is connected with the D ends of Q6 and a U23 field effect tube, the positive electrodes of C69 and C45 electrolytic capacitors, C41 and C42, the other end of C69 and the negative electrode of the C45 electrolytic capacitor are grounded, the other end of C41 is connected with the S end of U23, the D end of U24, C47, the other end of C47 and the S end of U24 are grounded, the other end of C42 is connected with the S end of Q6, the D end of Q8 and C44, the other end of C44 and the S end of Q8 are grounded, the S end of Q6 and the D end of Q8 are connected with the C40, R59, the other ends of the C40 and the R59 parallel circuit are connected with one end of a primary winding of a driving transformer T3, and the S end of U3 and the D end of U3; the G end of Q6 is connected with R62, the G end of Q8 is connected with R63, the other ends of R62 and R63 are connected with AA5, the G end of U23 is connected with R60, the G end of U24 is connected with R61, the other ends of R60 and R61 are connected with AA7, and the signal ends of AA5 and AA7 are respectively connected with the 14 and 11 pins of a U2 PWM chip on the main control platelet, namely the pulse width signal output end of the U2 PWM chip. The control signals output by the U2 PWM chip are two sets of square wave pulse signals. When a PWM pulse signal is output, PWM square wave pulses can be formed in a primary winding of the T3, and square wave pulse signals required for driving the IGBT can be generated in 4 driving circuits on the high-voltage side of the IGBT after coupling and isolation of the T3. The PWM signal is a signal for determining the output voltage and current of the inversion main circuit of the air plasma cutting machine. And the PWM signal is determined by a current regulation given signal Ug and a current negative feedback signal Ufi of the air plasma cutting machine.

Referring to fig. 2, when the cutter gun switch S is closed, the light emitting diode in the optocoupler U11 can be made to emit light, the output stage triode in the optocoupler is turned on, a +15V voltage is applied to both ends of the R19 resistor and the D4 diode, and the potential of the pin 5 of the operational amplifier U10 is higher than the potential of the pin 6 thereof, so that the pin 7 of the U10 outputs a high level, and since a C23 capacitor is connected between the pin 5 of the operational amplifier U10 and the pin 7 thereof, the circuit part of the operational amplifier U10 constitutes an integrating circuit, that is, the time when the pin 7 of the U10 outputs a high level lags behind the time when the cutter gun switch S is closed. When the pin 7 of the U10 outputs high, the transistor U12 is turned on, and +15V is applied to the anode of the diodes D16-1, D9, and D12.

Referring to the attached figure 2, when a cutting torch switch S is closed and the anode end of a D16-1 diode is at a high level, a U17-1 triode is conducted, a U16-1 triode is cut off or is not conducted, a light emitting diode in a U18 optocoupler does not emit light, and the AA-3 end is not grounded; on the contrary, when the anode terminal of the diode D9 is at a low level, the transistor U17-1 is turned off or not turned on, the transistor U16-1 is turned on, the light emitting diode in the U18 optocoupler emits light, the terminal AA-3 is grounded, and the diode D15 is turned on, and the diode D21 is turned off.

Referring to fig. 2, when the cutting torch switch S is closed and the anode terminal of the D9 diode is at a high level, the U7 fet is turned on, the pin 1 of the CN6 or 2CN4 plug is at a low level, the 2K2 relay operates, the contact 2K2-1 is closed, and the pin 1 or 3 of the 2CN3 plug is closed. 2CN3 plug is connected with the electromagnetic air valve of the cutting machine, therefore, the electromagnetic air valve will act to send the compressed air to the cutting gun.

Referring to fig. 2, a high frequency circuit board (HF-PCB) part, a plug 2CN1, is connected to two ends of a high frequency arc-striking winding of a T11 inverter main transformer, and when an inverter process occurs in an inverter main circuit, the two ends of the high frequency arc-striking winding have higher high frequency and high voltage; 2CN1-1 is connected with one end of a parallel circuit of a 2R1 resistor and a 2C2 capacitor, the other end of the parallel circuit is connected with one end of a contact 2K1-1 of a 2K1 relay, the other end of the contact 2K1-1 is connected with one end of a primary side of a high-frequency boosting transformer T1, and the other end of the primary side of the high-frequency boosting transformer T1 is connected with 2CN 1-3; the anode of the secondary output diode of the high-frequency step-up transformer T1 is connected with the resistor 2R2, the other end of the secondary output diode of the high-frequency step-up transformer T1 is connected with one end and M end of the high-frequency spark amplifier FD, the other end of the secondary output of the high-frequency step-up transformer T1 is connected with the other end of the high-frequency spark amplifier FD, one end of the high-voltage ceramic chip capacitors 2C1 and 2C1-1 which are connected in parallel, the other end of the high-voltage ceramic chip capacitors 2C1 and 2C1-1 which are connected in parallel is connected with the N end, the M, N end is connected with the primary ends of the T2 step-up coupling transformer in the output circuit of the cutting machine of the invention through the plug 2CN2 and the control line thereof, therefore, when the contact 2K1-1 is closed, the high-frequency high-voltage signal from the two end arc-leading windings of the inverse main transformer T11 is inverted (at this time, the cutting machine has no-load voltage established), and is boosted through T1, high-frequency high voltage is generated on the secondary side of the T1, when the voltage at two ends of the FD is high to a certain degree, the FD discharges and is short-circuited relative to two ends of the FD, at the moment, L, C (inductance and capacitance) oscillation is formed by the parallel high-voltage ceramic chip capacitors 2C1 and 2C1-1 and the primary side of the T2 boosting coupling transformer, and then the voltage is boosted and coupled through the T2, so that higher high-frequency high voltage is formed among a secondary circuit of the cutting machine, a cutting gun and a workpiece, and an air gap is broken through sufficiently to form plasma arcs.

Referring to fig. 2, when the cutting torch switch S is closed and the anode terminal of the D12 diode is at a high level, pin 8 of the U10 outputs a high level, the triode U8 is turned on, pin 3 of the CN6 and 2CN4 plugs is at a low level, the 2K1 relay is operated, and the contact 2K1-1 is closed, as described above, so that the circuit of the high-frequency arc striking part can operate, and conditions are created for finally forming a plasma arc and cutting.

Referring to the attached figure 2, the current detection and rectification conversion circuit consists of DLHGQ current transformers or current detection rings, D22-D25, an operational amplifier U19, capacitors C43 and C38, resistors R43, R53, R56, R64-R65 and a diode D20. The DLHGQ current transformer or the current detection ring is connected with the primary loop of the T11 inversion main transformer in series in the primary (1 turn), when the inversion process is formed and in the cutting process, the primary current signal of T11 can be detected at the secondary of the DLHGQ current transformer or the current detection ring, the detected current signal is rectified through the full bridge formed by D22-D25 to obtain a direct current signal, the capacitor C43 filters the direct current signal, the R64-R65 and the R43 and R53 series circuit are loads of the full bridge rectification, and the R43 and R53 series circuit is subjected to voltage division and then is used as the input signal of the U19 synchronous follower, so that the current feedback detection signal Ufi can be obtained at the 8-pin output end of the U19. The signal is filtered by D20 and C38 and is connected to an AA24 terminal, namely to one input terminal of a U1A operational amplifier on a control small board after being filtered by R56, and the current feedback detection signal Ufi of the terminal is connected to the inverting input terminal of the U1A operational amplifier through R1.

Referring to fig. 2, a direct current signal obtained by D-D full bridge rectification in the current detection and rectification conversion circuit is further connected to a high frequency cut-off control circuit, the high frequency cut-off control circuit is composed of two operational amplifiers in a U operational amplifier, specifically, the direct current signal obtained by D-D full bridge rectification is connected with an R resistor, the other end of the R is connected with a pin 12 of the U, a pin 13 of the U is connected with the R resistor, the R capacitor, the other end of the R is grounded, the other end of the R and the C is connected with a pin 14 of the U, the pin 14 of the U is connected with an anode of a diode D, a cathode of the D is connected with pins 3 of the R, C and the U, the other end of the R and the C is grounded, a pin 2 of the U is connected with the R and the R, the other end of the R is connected with +15V, the other end of the R is grounded, the pin 11 of the U is connected with +15V, a pin 1 of the U is connected with an anode of the diode D, and a cathode of the D is connected with a pin 9 of the U; when the current detection circuit detects a large current signal, 8 pins of the U10 can output low level through the circuit, at the moment, the electrolytic capacitor C24 discharges through the resistors R21 and R22, when the discharge reaches a certain degree, the triode U8 can be cut off, and because the discharge has certain time delay, after a short period of time when the current output of the cutting machine is detected, the triode U8 is cut off, the 2K1 relay can be powered off, so that the high-frequency arc striking is cut off through the contact 2K1-1 of the 2K1 relay, even if the high-frequency arc striking circuit stops generating a high-frequency high-voltage arc striking signal in an output loop of the cutting machine.

Referring to fig. 2, the current setting circuit is composed of an operational amplifier U19, an output current adjusting potentiometer, current correcting potentiometers RP1 and RP3, resistors R6, R55, R30-R32, a capacitor C9 and an electrolytic capacitor C27, wherein the output current adjusting potentiometer, the current correcting potentiometer RP1 and the RP3 are connected through a socket XH-3; the current correction potentiometers RP1 and RP3 can correct the maximum and minimum current output by the air plasma cutting machine; the maximum resistance end of a current setting potentiometer on the front panel of the cutting machine is connected with 3 pins of XH-3 and is simultaneously connected with one end of RP1, the middle sliding point of the current setting potentiometer on the front panel of the cutting machine is connected with 2 pins of XH-3, the minimum resistance end of the current setting potentiometer is connected with 1 pin of XH-3, the 1 pin of XH-3 is grounded, and the middle sliding point of RP1 and the other end of the middle sliding point are connected with + 15V; one end of RP3 is connected with +15V, the other end is grounded, the middle sliding point is connected with R32, and the other end of R32 is connected with the inverting input end of U19; the 2 pin of XH-3 is connected with C9 and R6, the other end of C9 is grounded, the other end of R6 is connected with R30, and the other end of R30 is connected with the 6-pin inverting input end of U19; an R31 and an electrolytic capacitor C27 are connected in parallel between the 6-pin inverting input end and the 7-pin output end of the U19, the positive polarity end of the C27 is connected with the 6-pin inverting input end of the U19, the output end of the U19 is connected with R55, and the other end of the R55 is connected with the AA21 end; the 5-pin non-inverting input end of the U19 is grounded; the output of the U19, which is the current set signal Ug of the chopper, is connected via R55 to the AA21 terminal, i.e. to the other input of the U1A operational amplifier on the control board, which is connected via R2 to the inverting input of the U1A operational amplifier.

Referring to fig. 2, the pin 2 of XH-3 is further connected with R15, the other end of R15 is connected with the pin 12 non-inverting input terminal of U10 operational amplifier, the pin 13 inverting input terminal of U10 operational amplifier is connected with the pin 14 of its output terminal to form a synchronous follower, the pin 14 of U10 operational amplifier is connected with one end of a correction potentiometer RP2, the middle sliding point of RP2 is connected with the pin 14 of U10 operational amplifier, the other end of RP2 is connected with R5, R23, the pin 5 CN2 (5) of socket CN2, the other end of R5 is connected with +5V, namely the pin 7 CN2 (7) of socket CN2, the other end of R23 is grounded, and a filter electrolytic capacitor C25 is connected between the pin 5 CN2 (5) of CN2 and the ground in parallel; the current setting data display table can be connected through a 7-pin CN2 (7) of a socket CN2, a 5-pin CN2 (5) of CN2 and a ground terminal. The part of the circuit is a current display circuit and is reserved, and the current given data display table is not arranged in the cutter of the invention, so the part of the circuit is reserved for forming a model with the ammeter. The current correction potentiometer RP2 can correct the difference between the data of the ammeter and the actual output current of the cutting machine.

Referring to fig. 2, the output characteristic control circuit is composed of a PWM chip U2 (UC 3846), an operational amplifier U1 (including four operational amplifiers U1A, U1B, U1C and U1D), a voltage regulator tube Z1, diodes D1-D4, and a plurality of resistors and capacitors around the devices; the circuit composed of the U1 and U1 operational amplifier parts is a synchronous follower, a pin 9 of the U1 is connected with a pin 8 of the U1, a pin 10 of the U1 is connected with a pin 8 of the U, C and C capacitors, the other ends of C and C are grounded, the pin 8 of the U1 is connected with one end of a series circuit of C capacitors, R resistors and C capacitors, the other end of the series circuit is connected with the other ends of C capacitors and R resistors and is connected to the other end of 4 pins, R and R of the U, the other end of R is grounded, the other end of R, namely an AA end is connected with the output end of a D-D rectifier bridge of a current detection circuit, the AA end is also connected with the C capacitors, R and R resistors, the other end of C is grounded, the other end of R is connected with a pin 16 of the U, namely a turn-off control end of the U, and the other end of R, namely the AA end is connected with + 15V; the 12 pin of the U1D operational amplifier is connected with resistors R5, R6 and a capacitor C4, the other ends of R6 and C4 are grounded, the other end AA16 of R5 is connected with the cathode of a diode D3, R4 and the anode of D3 are grounded, and the other end of R4 is connected with the output 1 pin of U1A; the pin 13 of the U1D operational amplifier is connected with the pin 14 thereof, and is also connected with an R7 resistor, the other end of R7 is connected with a C5 capacitor and a pin 5 of U2 (the non-inverting input end of the U2 internal error amplifier), and the other end of C5 is grounded; a pin 1 (CS end) of U2 is connected with the anode of AA3, R15 and C13 electrolytic capacitors, R16, AA3 is connected with the collector of an output stage triode in a U18 optical coupler, the other ends of R15 and C13 electrolytic capacitors are grounded, the other end of R16 is connected with a pin 2 (Vref end) of U2, the anode of C11 electrolytic capacitors and a pin 5 (non-inverting input end) of U1B, the other end of C11 electrolytic capacitors is grounded, a pin 6 (inverting input end) of U1B is connected with R18, R19 and C12, the other ends of R18 and C12 are grounded, the other end of R19 is connected with +15V, a pin 7 (output end) of U1B is connected with the anode of a diode D4, the cathode of D4 is connected with AA19 and R17, and the other end of R17 is connected with pins 16 (turn-off control end) of C14, R20, R8 and U2; pin 3 of U2 is grounded; the 4-pin of U2 connects C9 and C4, R12, R10, R11, R14; the 6 feet of the U2 are connected with the 7 feet thereof; the 11 pin of U2 is connected with AA7, and the 14 pin of U2 is connected with AA 5; the 12 pin of U2 is grounded, the 13 pin of U2 is connected with the positive electrodes of C16 and C17 electrolytic capacitors, the other ends of R23, C16 and C17 are grounded, and the other end of R23 and the 15 pin of U2 are connected with + 15V; AA21 is connected to pin 2 (inverting input) of U1A through R2, AA24 is connected to pin 2 (inverting input) of U1A through R1; the pin 3 (non-inverting input end) of the U1A is grounded, and two diodes D1 and D2 which are connected in an opposite phase mode are connected in parallel between the pin 2 of the U1A and the pin 3 of the U1A; a pin 2 of U1A is connected with the anode of a voltage regulator tube Z1 and R3, the cathode of Z1 is connected with a pin 1 (output end) of U1A, the other end of R3 is connected with C1, the other end of C1 is connected with a pin 1 of U1A, a pin 1 of U1A is connected with R4, and the other end of R4 is connected with the cathodes of AA16, R5 and D3; the circuit formed by the U1A operational amplifier part is a PI (proportional plus integral) operational control circuit, and the circuit formed by the U1B operational amplifier part is a voltage comparator; as already mentioned, the current set signal Ug is connected to the inverting input of the U1A operational amplifier via R2, and the current feedback detection signal Ufi is connected to the inverting input of the U1A operational amplifier via R1; the control signals of the 11 pins (AA 7) and the 14 pins (AA 5) of the U2 Pulse Width Modulation (PWM) chip output are two groups of square wave pulse signals which are used as the control signals of the IGBT driving circuit. The two groups of square-wave pulse signals have a fixed time difference in time, which is also known in the art as dead time. Is one of important parameters for ensuring the alternative work of the two groups of switches of the IGBT. The time is determined by the parameter settings of the peripheral devices (R21 and R22 at RT end and C7 and C8 at CT end) of the U2 chip. As to how to determine, the relevant usage data or description of UC3846 needs to be checked. And will not be repeated here. Here, it should be noted that: the PWM signal is a signal for determining the output voltage and current of the inversion main circuit of the air plasma cutting machine. And the PWM signal is determined by a current regulation given signal Ug and a current negative feedback signal Ufi of the air plasma cutting machine.

Referring to fig. 2, the thermal protection detection and control circuit is composed of a thermistor, a socket XH-RM, an operational amplifier U10 (the device pins of the operational amplifier U10 are 1 and 2/3), a resistor 9R 101-9R 105 arranged on the periphery of the operational amplifier U10, a capacitor 9C 101-9C 102, a diode 9D101 and an LED lamp (yellow) for indicating the panel overheating of the LEDY cutting machine; the thermistor is connected to the socket XH-RM; when the thermistor is installed, the temperature detection surface is closely attached to the radiator of the IGBT; in the output process of the cutting machine, when the radiator of the IGBT is overheated or when the thermistor (mounted close to the radiator of the IGBT) in the thermal protection detection and control circuit detects that the radiator of the IGBT is overheated, an operational amplifier U10 (the device pin of the operational amplifier U10 is 1, 2/3) in the thermal protection detection and control circuit turns over, so that an overheating protection indication LEDY lamp on the circuit board is turned on; meanwhile, the light emitting diode in the U18 emits light, and the triode inside the light emitting diode is conducted. The output signal of the optical coupler U18 is connected to the output characteristic control circuit of the main control panel, and the pulse output of the U2 PWM (UC 3846) chip can be closed through the output characteristic control circuit, so that the air plasma cutting machine stops outputting current. Under the action of the cooling fan, when the overheating phenomenon is eliminated, the control circuit can continue to output the PWM control signal. While the overheating indicator light (yellow) is extinguished. This achieves overheating protection for the air plasma cutter.

The working principle of other part of functional circuits of the air plasma cutting machine is briefly described as follows: as shown in FIG. 2, the terminals L and N are connected to a 220V-240V/50Hz power supply. After the power switch S1 is turned on, the air plasma cutter is powered on. A white power indicator light on its front panel lights up. Alternating current from a power grid is rectified into pulsating direct current through an input filter circuit and a rectifier BD 1. The rectified output firstly passes through a 3PTC1 thermistor, then C60-1, C60-2 and C60-3 large electrolytic capacitors (470 mu F/400V and the like) are charged, the voltage gradually rises, and finally the voltage is changed into stable +310V direct current and is output to a post-stage circuit from A, B.

As described above, in FIG. 2, the action time of the JR1 relay is delayed from the closing time of the power switch S1. Namely, the JR1 relay is time-delayed. When the charging voltage on the large electrolytic capacitors (470 muF/400V and the like) of C60-1, C60-2 and C60-3 is stable, the JR1 relay is operated, the contact is closed, and the 3PTC1 thermistor is short-circuited, so that when the air plasma cutting machine is in normal inversion operation, large current flows through the contact of the JR1 relay. Such a circuit is called a power-on buffer circuit. The power switch S1 is mainly prevented from being turned on at the moment, and large surge current is formed and the power switch S1 is burnt out due to the fact that no voltage exists on large electrolytic capacitors of C60-1, C60-2 and C60-3, which is equivalent to short circuit. The function of the power-on buffer circuit is to limit surge current by connecting a 3PTC1 thermistor in series at the moment of closing. The resistance of the 3PTC1 thermistor increases as its temperature increases. Therefore, the power-on buffer circuit can play a better protection role.

The large electrolytic capacitors of C60-1, C60-2 and C60-3 play a role of filtering. The +310V direct current is supplied to a full-bridge inverter main circuit which is composed of IGBT 1-IGBT 4 IGBT tubes, a T11 inverter main transformer, 9D1, 9D3, D6 and D8 fast recovery diodes, an output filter circuit and the like on the one hand, and the full-bridge inverter main circuit mainly has the functions of: under the action of an IGBT driving circuit and PWM pulses, high-voltage direct current is converted into medium-frequency (dozens of KHz) alternating current. The T11 inverter transformer realizes voltage reduction and conversion of large current output. The 9D1, 9D3, D6 and D8 fast recovery diodes convert the medium-frequency alternating current output by the inverter transformer into direct current. Because the converted current waveform is pulsating and unstable, and is not beneficial to the stability of the cutting process, the current filter reactor LX is adopted for filtering. Thus, the output current waveform becomes stable. Is beneficial to obtaining high-quality cutting seams.

On the other hand, the +310V direct current between A and B is supplied to a switching power supply circuit which is composed of a switching power supply transformer T4, optical couplers U11 and U28, a switching power supply PWM (pulse width modulation) control chip U30 (UC 3845B), U29 field effect transistors, 7805, 7815 and 7915 integrated voltage regulators, and surrounding resistors, capacitors, voltage regulators and the like, and the switching power supply circuit is used for generating +5V, +15V, +24V and-15V power supply voltages and supplying the voltages to corresponding control circuits for live working. For the switching power supply circuit part, in order to ensure the safety of a control circuit, a U11 photocoupler and a U28 photocoupler are used for isolation. The switching power supply circuit is divided into low-voltage side and high-voltage side circuit parts by the isolation of T4. In the low-voltage side circuit part of the switching power supply circuit, the secondary side of a switching power supply transformer T4 is provided with two windings, one is an independent secondary winding, the other is a secondary winding with a center tap, the latter is used for generating +5V, +15V, +24V and-15V power supplies, and the former is used for supplying power and controlling a switching control circuit of a cutting gun; for the independent secondary winding and the output power circuit part thereof, in the attached figure 2, S is a cutting gun switch which is arranged on the cutting gun, two control wires of the switch are connected to a two-core aviation socket below the front panel of the cutting machine through an aviation plug, and are connected to the output part in the switching power circuit through a connecting wire of the socket. When the cutting gun switch S is closed, the light emitting diode in the optocoupler U11 can emit light, and an output stage triode in the optocoupler is conducted to finally control other circuits of the cutting machine. Because the cutting torch switch line is longer, simultaneously, has the wire of heavy current in the cutting torch cable to also there is the wire that high frequency high-voltage signal passes through the cutting torch during the striking, consequently, can bring the interference to the switch control line of cutting torch, set up above-mentioned cutting torch switch line anti-jamming circuit, its effect is exactly utilizing the circuit of filter capacitor, inductance, opto-coupler etc. constitution, reduces the interference that comes from cutting torch switch control line, ensures cutting torch control circuit's reliable work.

After the switch S1 on the rear panel of the air plasma cutting machine is turned on to turn on the power supply source for a short time (during this time, the circuit of the air plasma cutting machine performs power-on buffering control and has certain delay control), the control boards inside the air plasma cutting machine are electrified to work. The white power supply on the front panel indicates that the LED lamp is on, and indicates that the air plasma cutting machine is electrified.

When the required cutting gun, the workpiece connecting cable and the compressed air supply system are connected and electrified, the air plasma cutting operation can be started. When an operator adjusts a given potentiometer signal Ug of cutting current on the front panel and presses a switch of a cutting gun to cut, under the action of a control circuit, a U2 PWM (UC 3846) pulse width control circuit on a main control panel inside the cutting machine generates a pulse signal with a large duty ratio, so that a driving circuit of the IGBTs works, two groups of the IGBTs are in an alternative conduction state, and finally, an inverter main circuit outputs no-load voltage. Meanwhile, the electromagnetic air valve acts to convey compressed air to the cutting gun; the high-frequency arc striking circuit works to generate a high-frequency high-voltage arc striking signal, and when the distance between the cutting gun and the workpiece meets the arc striking requirement, a plasma arc is formed; through a current detection ring or a current transformer, a current detection and rectification conversion circuit can detect a primary current signal of the transformer in the main inverter circuit, namely a current negative feedback signal Ufi. The current negative feedback signal Ufi is compared with a cutting current given signal Ug, PI (proportion and integral) regulation control is carried out on a compared difference signal through an output characteristic control circuit, and the output result of a PI circuit link controls AA5 and AA7 of a U2 PWM chip (UC 3846) to output pulse width or duty ratio. And then the on-off time of the IGBT in the inverter main circuit is controlled through a driving circuit of the IGBT, the output current and the voltage of the air plasma cutting machine are finally determined, the accurate control of the output current parameters is realized, and the output characteristic of the air plasma cutting machine is the constant-current descending characteristic. Further, when the current given signal Ug is unchanged, the current signal increases with the negative feedback Ufi detected by the circuit of the cutting machine, and after the given set value is reached, the difference between the current given Ug signal and the Ufi current negative feedback control signal decreases with the increase of the current, and after the PI control, the pulse width or duty ratio of the output PWM chip (UC 3846) of the cutting machine decreases, and the output voltage of the cutting machine decreases. This process, known as current-off negative feedback control, is a feedback control that is active only when the current reaches the set value of the current potentiometer. Thereafter, as the current increases slightly, the voltage decreases much. Along with the reduction of the voltage, the control circuit can increase the pulse width or the duty ratio of the U2 PWM chip (UC 3846), so that the cutting current is output according to the set parameters, and finally, the constant-current descending characteristic is formed. When the current set signal changes, the current cut-off negative feedback set value is different, but the other control processes are similar. In this way, between the minimum and maximum potentiometer settings, numerous droop characteristics can be obtained. Such control is also a basic requirement for meeting air plasma arc cutting. If the cutting machine is ready to not cut, the cutting gun is separated from the workpiece as long as the switch of the cutting gun is turned off, and the cutting machine is in a state of stopping output.

The operation of the circuit of other parts of the cutting machine is described in many ways due to the above parts. Are not described in detail herein.

The anti-interference measures of the hardware circuit of the cutting machine mainly comprise the following aspects:

1) and input to a filter circuit. Referring to fig. 2, the input filter circuit is composed of 7MT1, 7MT2 common mode inductors, 7R1 resistors and 7C 3-7C 7 capacitors, the 7C7 capacitors are connected in parallel to the two ends of the rear stage of the power switch S1 of the cutting machine, the 7MT1 common mode inductors are connected to the rear stage of the 7MT1 common mode inductors, the 7R1 resistors and the 7C5 capacitors are connected in parallel to the rear stage of the 7MT1 common mode inductors, one end of the 7MT1 common mode inductors is connected with the 7C3 capacitors, the other end of the 7MT1 common mode inductors is connected with the 7C4 capacitors, and the other ends of the 7C3 capacitors and the 7C4 capacitors are connected to a PE terminal (rack) or a protective grounding terminal of the cutting machine; the post-stage of the 7MT1 common mode inductor is connected with a 7MT2 common mode inductor, and the post-stage of the 7MT2 common mode inductor is connected with a 7C6 capacitor and the input end of a chopper rectifier BD1 in parallel. The input filter circuit can prevent interference signals from a power grid from entering a control circuit of the cutting machine on one hand, and can reduce interference signals generated by the cutting machine to enter the power grid on the other hand. The arrangement of the input filter circuit is one of important preconditions for ensuring that the cutting machine can pass EMC electromagnetic compatibility authentication, and is also one of important measures for resisting interference of a hardware circuit and improving the reliability of the cutting machine.

2) And an output filter circuit. Referring to the attached figure 2, an output filter circuit in a main circuit of the cutting machine consists of an output current filter inductor LX, resistors 9R 1-9R 6, filter capacitors 9C 1-9C 6, voltage dependent resistors 9VR2 and 9VR3, and diodes 9Z 1-9Z 3; 9R1 is connected in series with 9C1 and then connected in parallel across the output rectifying fast recovery diode 9D1, similarly 9R2 is connected in series with 9C2 and then connected in parallel across the output rectifying fast recovery diode D6; 9R3 is connected with 9C3 in series and then connected with two ends of an output rectifying fast recovery diode 9D3 in parallel; the 9R4 and the 9C4 are connected in series and then connected in parallel at two ends of an output rectifying fast recovery diode D8; the full-wave rectifying circuit is composed of D6, D8, 9D1 and 9D3, and the input end of the full-wave rectifying circuit is connected in parallel with two ends of a secondary output winding of the inverter main transformer T11; 9R5 is connected in parallel with the two ends of the output of the full-wave rectification circuit; the negative end of the full-wave rectification circuit is connected with an LX filter inductor, and a series circuit consisting of a 9R6 resistor, a 9C5 capacitor, a plug 9CN1, diodes 9Z 1-9Z 3 and a 9VR2 is connected in parallel between the other end of the LX filter inductor and the output positive polarity end of the full-wave rectification circuit; the series circuit is characterized in that: three positive polarity of 9Z 1-9Z 3 are connected in series, the anode end of 9Z1 is connected with the output positive polarity end of the full-wave rectification circuit, the cathode end of 9Z3 is connected with 9VR2, and 9VR2 is connected with the LX filter inductor and one end of an output high-frequency coupling transformer T2; the other end of the T2 is connected with a negative output end; the positive output terminal of the full-wave rectification circuit is also connected to the positive output terminal, and at the same time, one terminals of 9VR3 and 9C6 are also connected, and the other terminals of 9VR3 and 9C6 are connected to the PE terminal or protective ground terminal (frame) of the cutter. The output filter circuit can inhibit current fluctuation, reduce burr abrupt change signals in current waveforms, reduce spike interference signals in the rectification process of the fast recovery diode, simultaneously protect the fast recovery diodes D6, D8, 9D1 and 9D3, and prevent interference signals from the output end of the cutting machine from entering a control circuit of the cutting machine, so that the reliability of the cutting machine is improved.

3) And the IGBT switch and the inverter circuit are taken as anti-interference measures. Referring to fig. 2, in the input stage part of the IGBT inverter full bridge circuit, i.e. at both ends A, B, the anti-interference CBB capacitors C85 and C86 are connected in parallel; in the working process of the inverter main circuit, a peak interference signal can be generated in the on-off control process of the IGBT switching device. The interference signals are reduced or controlled by an anti-interference circuit connected with resistors and capacitors (such as R81, C21-1; R82, C22-1; R83, C23-1; R84, C24-1) at two ends of the IGBT device in parallel.

4) And (4) anti-interference measures of the direct-current power supply voltage. Referring to fig. 2, C59 and C60 antijamming capacitors are arranged between the input end of the +310V power supply leading-in switching power supply circuit and the rack or protective grounding; filter capacitors, such as C4, C12 and C18 capacitors, are arranged at the input end of a power supply circuit generating +5V, +15V and-15V; between the output of the +5V, +15V, -15V power supply and the ground, a filter capacitor, such as C2, C30, C30-1, is arranged; decoupling capacitors, such as C16, C17, C31 and C32, are provided between the operational amplifier +15V, -15V power supply to ground and the +15V power supply to ground of the PWM chip.

5) And (4) anti-interference measures for driving the IGBT. Referring to fig. 2, such as interference resisting capacitors of C29, C69, C41, C42, C44 and C47, and a filter circuit of a pi type formed by a C6 electrolytic capacitor, a C45 electrolytic capacitor and R58.

6) And (4) anti-interference measures of a cutting gun switch. Referring to fig. 2, S is a cutting torch switch, one end of the cutting torch switch S is connected to a filter inductor L1, the other end of the cutting torch switch S is connected to a filter inductor L2, the other end of the filter inductor L2 is connected to a cathode of D26, C18, an anode of an electrolytic capacitor C20, an R18 resistor, C11, and an anode of D26 is connected to a different-name end (an end without "●") of a secondary independent winding of a switching power supply transformer T4, the other end of the filter inductor L1 is connected to a cathode of a diode R11, C13, D3, and the other end of C11, the other end of R11 is connected to an anode of a light emitting diode in an optical coupler U11, and a cathode of the light emitting diode in the optical coupler U11, the other ends of C13 and C18, and R18, and a cathode of the electrolytic capacitor C20 are connected to a same-name end (an end with "●") of a secondary independent winding of the switching power supply transformer T4). When the cutting gun switch S is closed, the light emitting diode in the optocoupler U11 can emit light, and an output stage triode in the optocoupler is conducted to finally control other circuits of the cutting machine. Because the cutting torch switch line is longer, simultaneously, has the wire of heavy current in the cutting torch cable to also there is the wire that high frequency high-voltage signal passes through the cutting torch during the striking, consequently, can bring the interference to the switch control line of cutting torch, set up above-mentioned cutting torch switch line anti-jamming circuit, its effect is exactly utilizing the circuit of filter capacitor, inductance, opto-coupler etc. constitution, reduces the interference that comes from cutting torch switch control line, ensures cutting torch control circuit's reliable work.

In addition, there are measures for electromagnetic shielding in terms of structural design. The large control board 3 of the invention is vertically installed on the bottom board 11 of the machine shell, the small main control board 35 is welded on the large control board 3, the high-frequency control board 36 is installed on the large control board 3, and a sufficient creepage distance is reserved between the small main control board 35 and the large control board 3, so that the control circuit part of the cutting machine is equivalently surrounded by the metal shell consisting of the shell 2, the bottom board 11, the rear panel and the front panel, and the cutting machine can play roles of isolating strong electromagnetic interference, limiting electromagnetic radiation and the like.

The measures are one of the important prerequisites for ensuring the working reliability of the air plasma cutting machine product manufactured by the circuit of the invention.

The above is a brief description of the control process of each circuit part and the air plasma cutting process of the air plasma cutting machine of the present invention. Since the present invention has been shown in the schematic diagram of the air plasma cutting machine shown in fig. 1 and the schematic diagram of the detailed circuit shown in fig. 2, it is fully understandable for those who have the ability to read (or have knowledge about) the circuit. The circuit diagram is a silent language. However, even if more are explained, they are difficult for people without circuit reading ability (or knowledge of the associated circuits). In view of the space, only the major portions of the disclosure are set forth herein to provide the reader with a better understanding of the relevant principles of operation and processes.

From the foregoing description, it can be seen that the structure and circuitry of the slicer of the present invention has its own unique design considerations and methodologies. The air plasma cutting process method can be realized, and the designed control circuit and the whole structure of the air plasma cutting machine can also ensure that the air plasma cutting machine product meets the requirements of safety and electromagnetic compatibility certification, has good control performance, high electromagnetic compatibility and reliability, and is an important guarantee for meeting the requirements of high efficiency, low cost production and advanced manufacturing process technology of the product. The invention is in the structure and circuit design of the air plasma cutting machine.

In addition, the circuit boards are simple to connect, a lot of devices on the circuit boards are processed by adopting an automatic chip mounter and a component inserter, the manufacturing process and the production process are greatly simplified, and the product weight, the production cost and the transportation cost are reduced.

The above is a detailed description of the present invention in connection with specific air plasma cutter configurations and circuit boards and control functions, and it is not intended that the practice of the present invention be limited to these descriptions. Numerous other deductions and alterations may be made by those skilled in the art without departing from the spirit of the invention, which should be considered as falling within the scope of the invention.