阅读说明：本技术 变频器切换电路 (Frequency converter switching circuit ) 是由 刘明生 夏粒泉 于 2020-07-15 设计创作，主要内容包括：变频器切换电路,包括：断路器,所述断路器连接在主电线上；接触器,所述接触器通过电线与所述断路器连接；电机,所述电机通过内电线与所述接触器连接；变频器,所述变频器的输入端与输出端直接和所述接触器的两端并联连接。所述变频器切换电路把变频器主回路输出端用于切换旁路的接触器型开关装置取消,将变频器直接与接触器直接并联,使电路中,工频电源回路保持互相切换的功能,降低成本。由于不需要新增额外的接触器,还简化了电路结构,降价了电路故障发生的可能,节省了成本。(Converter switching circuit includes: a circuit breaker connected to a main power line; a contactor connected to the circuit breaker through a wire; the motor is connected with the contactor through an inner wire; and the input end and the output end of the frequency converter are directly connected with the two ends of the contactor in parallel. The frequency converter switching circuit cancels a contact type switch device for switching a bypass at the output end of a main loop of the frequency converter, and directly connects the frequency converter in parallel with a contactor, so that the power frequency power supply loop in the circuit keeps the function of mutual switching, and the cost is reduced. Because additional contactors do not need to be additionally arranged, the circuit structure is simplified, the possibility of circuit failure is reduced, and the cost is saved.)

1. A frequency converter switching circuit, comprising:

a circuit breaker connected to a main power line;

a contactor connected to the circuit breaker through a wire;

the motor is connected with the contactor through an inner wire;

and the input end and the output end of the frequency converter are directly connected with the two ends of the contactor in parallel.

2. The frequency converter switching circuit of claim 1, further comprising an intermediate relay having a normally open contact connected between the start terminal and a common terminal of an operational control loop of the frequency converter.

3. The frequency converter switching circuit according to claim 2, wherein the intermediate relay and the contactor constitute an electrical interlock structure, the electrical interlock structure including a normally closed contact of the contactor connected to a coil of the intermediate relay, the coil of the contactor connected to the normally closed contact of the intermediate relay.

4. The frequency converter switching circuit of claim 3, further comprising a relay activation circuit for controlling said intermediate relay.

5. The frequency converter switching circuit of claim 1, wherein an IGBT power module is employed for the output of the frequency converter.

6. The frequency converter switching circuit according to claim 1, wherein a three-phase power frequency voltage is directly applied to a load terminal of the frequency converter.

7. The frequency converter switching circuit according to claim 1, wherein the motor is a driving device of a water pump, a fan, a compressor, an air compressor, a transmission mechanism or a lifting mechanism.

8. The frequency converter switching circuit of claim 1, wherein the motor is a 110V three-phase ac motor, a 220V three-phase ac motor, a 380V three-phase ac motor, or a medium-high voltage motor within 13.6 kV.

9. The frequency converter switching circuit of claim 1, wherein the contactor coil voltage level is 24 vdc, 24 vac, 120 vac or 220 vac.

10. The frequency converter switching circuit of claim 2, wherein the intermediate relay has a coil voltage level of 24 vdc, 24 vac, 120 vac or 220 vac.

Technical Field

The invention relates to the technical field of electronic information, in particular to a frequency converter switching circuit.

Background

The wiring schematic diagram of the motor connected with the frequency converter is shown in fig. 1, the breaker QF1 is a loop manual switch for protection, and the contactor KM1 controls the loop to be switched on and off so as to start and stop the motor M. And the motor M is matched with a frequency converter VFD. In order to enable the motor M to be used under the original power supply circuit when the frequency converter fails, a wiring mode of adding a contactor KM2 is generally adopted to automatically switch the power supply circuit of the motor M as in fig. 1. In addition, as shown in fig. 2, compared with fig. 1, two contactors, namely contactor KM2 and contactor KM3, are added to achieve the purpose of switching the power supply circuit of the motor M.

It can be known that, the existing bypass switching function of the frequency converter needs to pass through at least two contact type switch type devices (contactor KM1 and contactor KM2), and often needs three contact type switch type devices (contactor KM1, contactor KM2 and contactor KM3), and the three contact type switch type devices are respectively responsible for the on-off of the power frequency power supply and the frequency converter loop, so as to ensure that when one of the two paths supplies power to the load, the other path is disconnected, and the bypass switching function is realized.

Because the circuit needs to be newly added with more than two contactors (namely, the contactor KM1, the contactor KM2 and even the contactor KM3 are also needed), the equipment cost is increased, the circuit fault point is increased, and the system reliability is reduced.

Disclosure of Invention

The invention aims to provide a frequency converter switching circuit, which reduces the circuit space occupation and the equipment cost, simplifies the connection of a circuit and reduces fault points.

In order to solve the above problems, the present invention provides a switching circuit of a frequency converter, including: a circuit breaker connected to a main power line; a contactor connected to the circuit breaker through a wire; the motor is connected with the contactor through an inner wire; and the input end and the output end of the frequency converter are directly connected with the two ends of the contactor in parallel.

Optionally, the circuit further comprises an intermediate relay, and a normally open contact of the intermediate relay is connected between the starting end and the common end of the operation control loop of the frequency converter.

Optionally, the intermediate relay and the contactor constitute an electrical interlock structure, the electrical interlock structure includes that the normally closed contact of contactor connects the coil of intermediate relay, the coil of contactor connects the normally closed contact of intermediate relay.

Optionally, the circuit further comprises a relay start circuit for controlling the intermediate relay.

Optionally, the output of the frequency converter adopts an IGBT power module.

Optionally, the load end of the frequency converter directly applies a three-phase power supply power frequency voltage.

Optionally, the motor is a driving device of a water pump, a fan, a compressor, an air compressor or a transmission mechanism.

Optionally, the motor is a 110V three-phase alternating current motor, a 220V three-phase alternating current motor, a 380V three-phase alternating current motor, or a medium-high voltage motor within 13.6 kV. Optionally, the coil voltage level of the contactor is 24V dc voltage, 24V ac voltage, 120V ac voltage or 220V ac voltage.

Optionally, the coil voltage level of the intermediate relay is 24V dc voltage, 24V ac voltage, 120V ac voltage or 220V ac voltage.

In one aspect of the technical scheme, the contact type switch device for switching the bypass at the output end of the main loop of the frequency converter is eliminated, and the frequency converter is directly connected with a contactor in parallel, so that the power frequency power supply loops in the circuit keep the function of mutual switching, and the cost is reduced. Because additional contactors do not need to be additionally arranged, the circuit structure is simplified, the possibility of circuit failure is reduced, and the cost is saved.

Meanwhile, the input end and the output end of the frequency converter are directly connected with the two ends of the contactor in parallel, the function of mutual switching with the power frequency power supply loop is realized, the space occupation is reduced, the equipment cost is reduced, the connection on a line is simpler, and the fault points are reduced.

Furthermore, an intermediate relay and a contactor are utilized to form electrical interlocking, the function that the motor, the power frequency power supply and the frequency converter loop are mutually switched is realized, and the switching between the original loop and the frequency converter loop can be realized without additional on-off control of a main loop contactor. The structure is simple and efficient, the device is suitable for frequency converters with various voltages and similar electrical equipment, and the overall cost is reduced.

Drawings

FIG. 1 is a circuit diagram of a conventional frequency converter;

FIG. 2 is a circuit diagram of another conventional converter switching circuit;

FIG. 3 is a circuit diagram of a switching circuit of a frequency converter according to an embodiment of the present invention;

FIG. 4 is a circuit diagram of a switching circuit of a frequency converter according to another embodiment of the present invention;

QF 1-circuit breaker; KM 1-contactor; m-motor; a VFD-converter; KM 2-contactor; KM 3-contactor; KM 11-contactor main contact; KM 12-contactor normally closed contact; KM 13-contactor coil; KA 1-intermediate relay; KA 11-normally open contact of intermediate relay; KA 12-intermediate relay coil; KA 13-intermediate relay normally closed contact; VFD 1-frequency converter control loop; s1-starting end of control loop; SC-control loop common; s6-control loop switch.

Detailed Description

It can be known from the background art that the existing circuit for switching the bypass of the frequency converter needs to be respectively responsible for the on-off of the power frequency power supply and the loop of the frequency converter through at least two contact type switch devices, so as to ensure that when one of the circuits supplies power to the load, the other circuit is switched off, thereby realizing the bypass switching function. One or two contactors are added in the method, so that the equipment cost is improved, the circuit fault points are increased, and the system reliability is reduced.

Therefore, the present invention provides a new switching circuit of a frequency converter to solve the above-mentioned disadvantages.

For a more clear presentation, the invention is described in detail below with reference to the accompanying drawings.

An embodiment of the present invention provides a frequency converter switching circuit, please refer to fig. 1, including:

a breaker QF1, wherein the breaker QF1 is connected to the main power line;

a contactor KM1, in the embodiment, the contactor KM1 is an AC contactor KM1, and the contactor KM1 is connected with a breaker QF1 through a wire;

the motor M is connected with the contactor KM1 through an inner wire;

the input end and the output end (the output end is usually also called a load end) of the frequency converter VFD are directly connected in parallel with two ends of the contactor KM1 (usually, the positive and negative poles of a bus of the frequency converter VFD can be connected with a circuit breaker QF 1).

The converter switching circuit that this embodiment provided, the switching device (contactor) that is used for switching the bypass to converter VFD major loop output cancel, but, through circuit design and circuit principle, still can guarantee to realize keeping the function of switching each other with power frequency power supply circuit, reduce cost. Because additional contactors do not need to be additionally arranged, the circuit structure is simplified, the possibility of circuit failure is reduced, and the cost is saved. That is to say, in this embodiment, converter VFD input and output are directly connected in parallel with contactor KM1 both ends, realize keeping the function of switching each other with the power frequency power supply circuit. Because a contact type switch device is eliminated, the occupied space is reduced, the equipment cost is reduced, the connection on a line is simpler, and the fault points are reduced.

Another embodiment of the present invention provides another frequency converter switching circuit, including:

a breaker QF1, wherein the breaker QF1 is connected to the main power line;

the contactor KM1 is connected with a breaker QF1 through a wire, and the contactor KM1 is connected with the breaker QF1 through a wire;

the motor M is connected with the contactor KM1 through an inner wire;

and the input end and the output end of the frequency converter VFD are directly connected with two ends of the contactor KM1 in parallel.

In the above, reference may be made to the corresponding contents of the foregoing embodiments.

Unlike the previous embodiment, in this embodiment, the inverter switching circuit further includes an intermediate relay KA1, and a normally open contact of the intermediate relay KA1 is connected between the start terminal and the common terminal of the operation control circuit of the inverter VFD.

Unlike the previous embodiment, in the present embodiment, the intermediate relay KA1 and the contactor KM1 form an electrical interlock structure, and the electrical interlock structure includes: the main contact KM11 of the contactor KM1 is connected to the circuit and between the breaker QF1 and the motor M, the normally closed contact KM12 of the contactor KM1 is connected to the coil KA12 of the intermediate relay KA1, and the coil KM13 of the contactor KM1 is connected to the normally closed contact KA13 of the intermediate relay KA 1. Such interconnecting circuit wires forming an electrical interlock arrangement are shown in phantom in fig. 4. The contactor KM1 includes a main contact KM11, a normally closed contact KM12, a coil KM13, and a normally open contact (not shown because the normally open contact is not required in this embodiment).

Meanwhile, this embodiment also shows some circuit structures of the inverter VFD in the loop, that is, a part of the control circuit of the inverter VFD, that is, a part of the operation control loop VFD 1. Specifically, as described above, the normally open contact KA11 of the intermediate relay KA1 is connected between the start terminal S1 (start control terminal) of the operation control circuit VFD1 of the inverter VFD and the common terminal SC. The intermediate relay KA1 does not distinguish between main contacts and auxiliary contacts, and includes a normally open contact KA11, a coil KA12, and a normally closed contact KA 13.

The starting end S1 closes the common end SC, then the loop of the frequency converter VFD is switched on, the frequency converter VFD is started, and the frequency converter VFD outputs corresponding voltage to start the motor M; when the start terminal S1 is disconnected from the common terminal SC, the frequency converter VFD is turned off, and the frequency converter VFD turns off the output voltage. That is, the start terminal S1 and the common terminal SC are closed to start the frequency converter VFD, and are not closed to stop the frequency converter VFD. Therefore, the circuit of the embodiment is ensured not to be simultaneously powered by the contactor KM1 and the frequency converter VFD 1. The switch S6 is another switch of the inverter VFD operation control loop VFD 1.

The wiring mode of the embodiment is simpler, the intermediate relay KA1 is not necessary, and only when the electrical interlocking is needed to be realized, the intermediate relay KA1 is added, and the main idea of the invention is that the lower side (or the upper side) of the frequency converter is not additionally provided with other contactors, and is directly connected with the contactor KM1 in parallel.

Meanwhile, the intermediate relay KA1 is adopted in the embodiment, and the intermediate relay KA1 is more cost-saving and smaller in size than a contactor.

It should be noted that, in other embodiments, the frequency converter switching circuit may further include a relay start circuit for controlling the intermediate relay KA1, and the corresponding start circuit may be designed to be simpler and smaller, and may even be directly attached to the intermediate relay KA 1.

In this embodiment, the output of the frequency converter VFD may adopt an IGBT (insulated gate bipolar transistor) power module. The IGBT is a compound fully-controlled voltage-driven power semiconductor device composed of BJT (bipolar transistor) and MOSFET (insulated gate field effect transistor), and has the advantages of both high input impedance of MOSFET and low on-state voltage drop of GTR (power transistor).

In this embodiment, the load end of the VFD directly applies the power frequency voltage of the three-phase power supply. The design simultaneously enables the power supply to connect 380V alternating current voltage to the output interface of the VFD of the frequency converter for a long time, namely the power supply can directly apply industrial frequency alternating current voltage to the output end of the frequency converter for a long time. That is, when the VFD is not started, the power supply can directly apply the power frequency ac voltage to the output terminal of the VFD for a long time without causing the problems of the frequency converter damage and the circuit failure, as shown in fig. 4.

In this embodiment, the motor M may be a driving device of a water pump, a fan, a compressor, an air compressor, or a transmission mechanism. The motors of the devices are controlled by the frequency converter switching circuit provided by the embodiment, so that the control effect is good, and faults are not easy to occur (because the connection points are reduced).

In this embodiment, the motor M may be a 110V three-phase ac motor, a 220V three-phase ac motor, a 380V three-phase ac motor, or a medium-high voltage motor within 13.6 kV. The medium-high voltage motor within 13.6kV can be 6600V, 3800V, 1140V, 660V or 460V motor.

In this embodiment, the coil KM13 of the contactor KM1 may have a voltage level of 24V dc voltage, 24V ac voltage, 120V ac voltage or 220V ac voltage.

In this embodiment, the voltage level of the coil KA12 of the intermediate relay KA1 may be 24V dc voltage, 24V ac voltage, 120V ac voltage, or 220V ac voltage.

In the new connection and control mode (converter switching circuit) for switching the output end of the converter provided by this embodiment, the input end and the output end of the converter VFD are directly connected in parallel with the two ends of the contactor KM 1.

Furthermore, an intermediate relay KA1 and a contactor KM1 form electrical interlocking, and switching between an original loop and a frequency converter loop can be realized without additional on-off control of a main loop contactor. When the VFD of the frequency converter is not started, the power supply can directly apply power frequency alternating voltage to the output end of the frequency converter for a long time, and the problems of frequency converter damage and loop are avoided.

The wiring method cancels a contact type switch device, reduces the space occupation and the equipment cost, is simpler to connect on a line and reduces the fault points. Compared with the original scheme, the method has obvious cost advantage and good technical and economic benefits.

The novel connection and control mode for switching the output end of the frequency converter is that a contact type switch device for switching the bypass is cancelled at the output end of a main loop of the frequency converter, the input end and the output end of the frequency converter are directly connected with two ends of a contactor KM1 in parallel, and an intermediate relay KA1 and the contactor KM1 are utilized to form electrical interlocking, so that the function of mutually switching a motor, a power frequency power supply and a frequency converter loop is realized, and the switching between the original loop and the frequency converter loop can be realized without additional on-off control of a contactor of the main loop. The structure is simple and efficient, and the device is suitable for frequency converters with various voltages and similar electrical equipment, so that the overall cost is greatly reduced.

The novel connection and control mode for switching the output ends of the frequency converter adopts the mode that the input end and the output end of the frequency converter VFD are directly connected with two ends of the contactor KM1 in parallel, the switching device for switching the bypass is cancelled at the output end of the main loop of the frequency converter VFD, the function of mutual switching between the frequency converter and the power frequency power supply loop is better realized aiming at a load motor, and the electric interlocking effect is realized, so that the better protection effect is achieved.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.