阅读说明：本技术 一种交流电机变频起动器 (Variable frequency starter of alternating current motor ) 是由 袁守民 于 2021-01-12 设计创作，主要内容包括：本发明公开了一种交流电机变频起动器,涉及电机起动控制技术领域,本发明的主要技术方案为：包括三相全控整流单元、三相旋转换流变频单元及中央处理控制单元,所述三相全控整流单元与三相电源连接,用于将所述三相电源转换输出为可控直流电压,所述三相旋转换流变频单元的输入端与所述三相全控整流单元的输出端连接,用于输出三相互差120°的变频电压,所述三相旋转换流变频单元的输出端通过第二支路连接电机,所述第二支路上设置有第二接触器；第一支路,用于连接所述三相电源和所述电机,所述第一支路上设置有第一接触器,且所述中央处理控制单元用于控制所述第一接触器和所述第二接触器。(The invention discloses an alternating current motor variable frequency starter, which relates to the technical field of motor starting control, and the main technical scheme of the invention is as follows: the three-phase full-control rectification unit is connected with a three-phase power supply and used for converting and outputting the three-phase power supply into controllable direct-current voltage, the input end of the three-phase rotary commutation frequency conversion unit is connected with the output end of the three-phase full-control rectification unit and used for outputting three-phase variable-frequency voltage with 120 degrees of mutual difference, the output end of the three-phase rotary commutation frequency conversion unit is connected with a motor through a second branch, and a second contactor is arranged on the second branch; the first branch circuit is used for connecting the three-phase power supply and the motor, a first contactor is arranged on the first branch circuit, and the central processing control unit is used for controlling the first contactor and the second contactor.)

1. An alternating current motor variable frequency starter, comprising:

the three-phase full-control rectification unit is connected with a three-phase power supply and used for converting and outputting the three-phase power supply into controllable direct-current voltage, the input end of the three-phase rotary commutation frequency conversion unit is connected with the output end of the three-phase full-control rectification unit and used for outputting three-phase variable-frequency voltage with 120 degrees of mutual difference, the output end of the three-phase rotary commutation frequency conversion unit is connected with a motor through a second branch, and a second contactor is arranged on the second branch;

the first branch circuit is used for connecting the three-phase power supply and the motor, a first contactor is arranged on the first branch circuit, and the central processing control unit is used for controlling the first contactor and the second contactor;

the phase sequence phase detection unit and the phase sequence phase locking unit, wherein the input end of the phase sequence phase detection unit is connected with the three-phase power supply, the output end of the phase sequence phase detection unit and the output end of the three-phase rotary commutation frequency conversion unit are connected with the input end of the phase sequence phase locking unit, and the output end of the phase sequence phase locking unit is connected with the central processing control unit.

The input end of the trigger voltage-regulating control unit is connected with the central processing control unit, and the output end of the trigger voltage-regulating control unit is connected with the three-phase full-control rectifying unit;

the input end of the rectified voltage detection unit is connected with the output end of the three-phase fully-controlled rectification unit, and the output end of the rectified voltage detection unit is connected with the central processing control unit;

the input end of the rotating speed control unit is connected with the central processing control unit, and the output end of the rotating speed control unit is connected with the three-phase rotating current conversion frequency conversion unit;

and the motor current detection unit is used for detecting the current of the motor and feeding the current back to the central processing control unit.

2. The AC motor variable frequency starter according to claim 1, wherein the three-phase rotary converter frequency conversion unit comprises a servo motor, a main shaft connected to the servo motor, and a V + slip ring, a V-slip ring and an alternating slip ring which are sequentially arranged on the main shaft, the alternating slip ring comprises an insulator connected to the main shaft and a V + half ring and a V-half ring which are symmetrically arranged at two sides of the insulator, a V + carbon brush is arranged at the outer side of the V + slip ring and electrically connected with the V + slip ring, the V + slip ring and the V + half ring are connected to form a V + voltage half ring, a V-carbon brush is arranged at the outer side of the V-slip ring and electrically connected with the V-half ring to form a V-voltage half ring, and a U-phase carbon brush and a carbon brush are arranged at the outer side of the alternating slip ring and electrically connected with the V, The carbon brush comprises a V-phase carbon brush and a W-phase carbon brush, and 120-degree included angles are formed among connecting lines of the U-phase carbon brush, the V-phase carbon brush and the W-phase carbon brush and the axis of the spindle respectively.

3. The ac motor variable frequency starter of claim 2 wherein the V + slip ring and the V + half ring are connected by a V + copper busbar.

4. The ac motor variable frequency starter of claim 2 wherein the V-slip ring and the V-half ring are connected by a V-copper busbar.

Technical Field

The invention relates to the technical field of motor starting control, in particular to an alternating current motor variable frequency starter.

Background

When the asynchronous motor commonly used in industrial and agricultural production is directly started, 5 to 7 times rated impulse current can be generated, particularly, when a large motor is started, the voltage of a power grid can be reduced, and the operation of other electrical equipment in the same power supply system is influenced, so that the starting modes of the conventional and commonly used alternating current asynchronous motor mainly comprise starting modes such as autotransformer starting, star-delta starting, silicon controlled soft starting and the like, the starters have the common characteristic of voltage reduction starting, but still generate 3 to 4 times of impulse current, the starting difficulty can still be caused under the conditions that a power supply line is longer and the load is heavier (such as a large mine fan), and the impulse current generated by the voltage reduction starting of a permanent magnet synchronous motor which is formed in recent years can also cause the demagnetization deterioration of a permanent magnet so as to reduce the rated output power of.

The frequency conversion starting mode of the alternating current motor is a recognized optimal starting mode, and can realize that rated torque is generated under the condition of about 1 time of rated current to finish the starting process of the motor, so the frequency conversion starting mode can reduce the capacity of a power supply transformer and the cost of a long-distance power supply cable. Therefore, the variable frequency starter of the alternating current motor is provided.

Disclosure of Invention

In view of this, the embodiment of the present invention provides a variable frequency starter for an ac motor, and the present invention mainly provides the following technical solutions:

in one aspect, an embodiment of the present invention provides an ac motor variable frequency starter, including: the three-phase full-control rectification unit is connected with a three-phase power supply and used for converting and outputting the three-phase power supply into controllable direct-current voltage, the input end of the three-phase rotary commutation frequency conversion unit is connected with the output end of the three-phase full-control rectification unit and used for outputting three-phase variable-frequency voltage with 120 degrees of mutual difference, the output end of the three-phase rotary commutation frequency conversion unit is connected with a motor through a second branch, and a second contactor is arranged on the second branch;

the first branch circuit is used for connecting the three-phase power supply and the motor, a first contactor is arranged on the first branch circuit, and the central processing control unit is used for controlling the first contactor and the second contactor;

the phase sequence phase detection unit and the phase sequence phase locking unit, wherein the input end of the phase sequence phase detection unit is connected with the three-phase power supply, the output end of the phase sequence phase detection unit and the output end of the three-phase rotary commutation frequency conversion unit are connected with the input end of the phase sequence phase locking unit, and the output end of the phase sequence phase locking unit is connected with the central processing control unit.

The input end of the trigger voltage-regulating control unit is connected with the central processing control unit, and the output end of the trigger voltage-regulating control unit is connected with the three-phase full-control rectifying unit;

the input end of the rectified voltage detection unit is connected with the output end of the three-phase fully-controlled rectification unit, and the output end of the rectified voltage detection unit is connected with the central processing control unit;

the input end of the rotating speed control unit is connected with the central processing control unit, and the output end of the rotating speed control unit is connected with the three-phase rotating current conversion frequency conversion unit;

and the motor current detection unit is used for detecting the current of the motor and feeding the current back to the central processing control unit.

Optionally, the three-phase rotating current conversion frequency conversion unit includes a servo motor, a main shaft connected to the servo motor, and a V + slip ring, a V-slip ring and an alternating slip ring sequentially disposed on the main shaft, the alternating slip ring includes an insulator connected to the main shaft, and a V + half ring and a V-half ring symmetrically disposed on two sides of the insulator, a V + carbon brush electrically connected to the V + slip ring is disposed on an outer side of the V + slip ring, the V + slip ring is connected to the V + half ring to form a V + voltage half ring, a V-carbon brush electrically connected to the V-slip ring is disposed on an outer side of the V-slip ring, the V-slip ring is connected to the V-half ring to form a V-voltage half ring, and a U-phase carbon brush, a V-phase carbon brush and a W-phase carbon brush electrically connected, and the U-phase carbon brush, the V-phase carbon brush and the W-phase carbon brush respectively form an included angle of 120 degrees with a connecting line of the axis of the spindle.

Optionally, the V + slip ring and the V + half ring are connected by a V + conductive copper bar.

Optionally, the V-slip ring and the V-half ring are connected by a V-conductive copper bar.

The alternating current motor variable frequency starter provided by the embodiment of the invention has the advantages of small starting current, larger starting torque, simple and reliable structure and lower cost, can be suitable for various alternating current motors, and is a special variable frequency starter with stepless frequency conversion from 0 to power frequency.

Drawings

Fig. 1 is a schematic diagram of a control system of an ac motor variable frequency starter according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a three-phase rotating, commutating and frequency converting unit of an ac motor frequency converting starter according to an embodiment of the present invention;

FIG. 3 is a schematic view of the cross-sectional structure A-A of FIG. 2;

fig. 4 is a schematic voltage waveform diagram of U-phase carbon brushes, V-phase carbon brushes and W-phase carbon brushes of the variable frequency starter of the ac motor according to the embodiment of the present invention;

fig. 5 is a schematic diagram of line voltage waveforms of a U-phase carbon brush, a V-phase carbon brush, and a W-phase carbon brush of the variable frequency starter of the ac motor according to the embodiment of the present invention;

fig. 6 is a schematic diagram illustrating position changes of a U-phase carbon brush, a V-phase carbon brush, and a W-phase carbon brush of a V + half ring and a V-half ring of a variable frequency starter of an ac motor according to an embodiment of the present invention;

in the figure: the three-phase power supply comprises a three-phase power supply 1, a three-phase fully-controlled rectifying unit 2, a three-phase rotating commutation frequency conversion unit 3, a main shaft 301, a V + slip ring 302, a V-slip ring 303, an insulator 304, a V + half ring 305, a V-half ring 306, a V + carbon brush 307, a V-carbon brush 308, a U-phase carbon brush 309, a V-phase carbon brush 310, a W-phase carbon brush 311, a V + conductive copper bar 312, a V-conductive copper bar 313, a servo motor 314, a central processing control unit 4, a second contactor 6, a first contactor 7, a phase sequence phase detection unit 8, a phase sequence phase locking unit 9, a trigger voltage regulation control unit 10, a rectifying voltage detection unit 11, a motor current detection unit 12 and a.

Detailed Description

To further illustrate the technical means and effects of the present invention adopted to achieve the predetermined objects, the following detailed description of the variable frequency starter for ac motor according to the present invention with reference to the accompanying drawings and preferred embodiments shows the following detailed descriptions of the specific implementation, structure, features and effects thereof.

Example one

Referring to fig. 1 to 6, an embodiment of the present invention provides an ac motor variable frequency starter, including: the three-phase full-control rectification unit 2 is connected with a three-phase power supply 1 and used for converting and outputting the three-phase power supply 1 into voltage-controllable direct-current voltage, the three-phase rotary commutation frequency conversion unit 3 is connected with the three-phase full-control rectification unit 2 and used for outputting three-phase variable-frequency voltage with 120 degrees of mutual difference, the output end of the three-phase rotary commutation frequency conversion unit 3 is connected with a motor 5 through a first branch, a second contactor 6 is arranged on the first branch and positioned at one side of the second contactor 6, a second branch used for being connected with the central processing control unit 4 is arranged on the first branch, a first contactor 7, a phase sequence phase detection unit 8 and a phase sequence phase locking unit 9 are connected on the second branch, the phase sequence phase locking unit 9 is connected with the first branch and connected to the other side of the second contactor 6, the central processing control unit 4 is used for controlling the first contactor 7 and the second contactor 6, a trigger voltage regulation control unit 10 is connected between the central processing control unit 4 and the three-phase full-control rectification unit 2, the central processing control unit 4 is connected with an output end of a rectification voltage detection unit 11, an input end of the rectification voltage detection unit 11 is connected between the three-phase full-control rectification unit 2 and the three-phase rotary commutation frequency conversion unit 3, a rotating speed control unit 13 is connected between the central processing control unit 4 and the three-phase rotary commutation frequency conversion unit 3, and a motor current detection unit 12 is connected between the central processing control unit 4 and the motor 5.

The three-phase full-control rectification unit 2 is connected with a three-phase power supply and used for converting and outputting the three-phase power supply into controllable direct-current voltage, the input end of the three-phase rotary commutation frequency conversion unit 3 is connected with the output end of the three-phase full-control rectification unit 2 and used for outputting three-phase variable-frequency voltage which is 120 degrees different from each other, the output end of the three-phase rotary commutation frequency conversion unit 3 is connected with a motor through a second branch, and a second contactor 6 is arranged on the second branch;

the first branch circuit is used for connecting the three-phase power supply and the motor, a first contactor 7 is arranged on the first branch circuit, and the central processing control unit 4 is used for controlling the first contactor 7 and the second contactor 6;

the phase sequence phase detection unit 8 and the phase sequence phase locking unit 9, an input end of the phase sequence phase detection unit 8 is connected to the three-phase power supply, an output end of the phase sequence phase detection unit 8 and an output end of the three-phase rotating commutation frequency conversion unit 3 are connected to an input end of the phase sequence phase locking unit 9, and an output end of the phase sequence phase locking unit 9 is connected to the central processing control unit 4.

The input end of the trigger voltage-regulating control unit 10 is connected with the central processing control unit 4, and the output end of the trigger voltage-regulating control unit 10 is connected with the three-phase full-control rectifying unit 2;

the input end of the rectified voltage detection unit 11 is connected with the output end of the three-phase fully-controlled rectification unit 2, and the output end of the rectified voltage detection unit 11 is connected with the central processing control unit 4;

the input end of the rotating speed control unit 13 is connected with the central processing control unit 4, and the output end of the rotating speed control unit 13 is connected with the three-phase rotating current conversion frequency conversion unit 3;

and a motor current detection unit 14 for detecting the current of the motor and feeding the current back to the central processing control unit 4.

Specifically, a three-phase power supply 1 is converted into voltage-controllable direct-current voltage through a three-phase fully-controlled rectifying unit 2, three-phase variable-frequency voltage with 120 degrees of difference is output through a three-phase rotating current-converting frequency conversion unit 3, a central processing control unit 4 adopts a control principle that magnetic flux is unchanged, the voltage is changed while frequency is changed, namely a VVVF control scheme, according to the load, the frequency converter is provided with proper starting time, the central processing control unit 4 controls output frequency and three-phase voltage to continuously rise, when the frequency rises to the same grid frequency, a motor 5 reaches a rated rotating speed, the central processing control unit 4 detects the phase sequence and phase difference of the grid and the phase sequence phase difference of the frequency converter through a phase sequence detection unit 8, the phase sequence phase of the frequency converter is adjusted, a second contactor 6 (CJ 2) is disconnected at a proper position, a first contactor 7 (CJ 1) is switched on to realize the conversion from the variable, and finishing the variable frequency starting process of the alternating current motor.

Further, in a specific implementation, the three-phase rotating commutating frequency conversion unit 3 includes a servo motor 314, a main shaft 301 connected to the servo motor, and a V + slip ring 302, a V-slip ring 303 and an alternating slip ring sequentially disposed on the main shaft 301, where the alternating slip ring includes an insulator 304 connected to the main shaft 301, and a V + half ring 305 and a V-half ring 306 symmetrically disposed on both sides of the insulator 304, a V + carbon brush 307 electrically connected to the V + slip ring 302 is disposed outside the V + slip ring 302, the V + slip ring 302 and the V + half ring 305 are connected to form a V + voltage half ring, a V-308 electrically connected to the V-slip ring 303 is disposed outside the V-slip ring 303, the V-slip ring 303 and the V-half ring 306 are connected to form a V-voltage half ring, and a U-phase carbon brush 309, a V-half ring 306, a V-, The angle between the connection line of the U-phase carbon brush 309, the connection line of the V-phase carbon brush 310, the connection line of the W-phase carbon brush 311, and the connection line of the U-phase carbon brush 309, the connection line of the V-phase carbon brush 310, and the connection line of the W-phase carbon brush 311, and the axis of the spindle 301 is 120 degrees.

Specifically, the V + slip ring 302 is connected with the V + half ring 305 to form a V + voltage half ring, the V-slip ring 303 is connected with the V-half ring 306 to form a V-voltage half ring, and the frequency conversion working principle is as follows: the three-phase fully-controlled rectifying unit 2 outputs adjustable direct-current voltage V +, V-is connected with a V + carbon brush 307 and a V-carbon brush 308, two V + semi-rings 305 and V-semi-rings 306 which are insulated from each other are led in through a V + slip ring 302 and a V-slip ring 303, a servo motor 314 drives the V + slip ring 302, the V-slip ring 303, the V + semi-rings 305 and the V-semi-rings 306 to synchronously rotate when rotating, the servo motor 314 is controlled by a central processing control unit 4 to rotate, the central processing control unit 4 gradually increases the rotating speed according to the starting time set by a user and the current value (below the allowed current of a motor 5) when the motor 5 operates, the central processing control unit 4 controls the three-phase fully-controlled rectifying unit 2 to proportionally increase the output voltage and realize variable-frequency variable-voltage VVVF control when the rotating speed of the servo motor 314 is increased from 0 to 50 revolutions per second to rated, the U-phase carbon brushes 309, the V-phase carbon brushes 310 and the W-phase carbon brushes 311 which are arranged on the V + semi-ring 305 and the V-semi-ring 306 obtain 50Hz positive and negative symmetrical square wave voltage, the phase voltage waveform U, V, W waveforms of the square wave voltage are shown in figure 4, the line-to-line voltage waveforms UV, VW and WU waveforms are shown in figure 5 because the installation positions of the U-phase carbon brushes 309, the V-phase carbon brushes 310 and the W-phase carbon brushes 311 are different by 120 degrees from each other, and when the rotating speed of the motor 5 is gradually increased from 0 rotating speed to 50 revolutions per second or 60 revolutions per second, three-phase power frequency alternating current with 120 degrees from each other can be obtained.

Further, in a specific implementation, the V + slip ring 302 and the V + half ring 305 are connected by a V + conductive copper bar 312.

Further, in a specific implementation, the V-slip ring 303 and the V-half ring 306 are connected through a V-copper conducting bar 313.

It should be noted that in the description of the present specification, the terms "upper", "lower", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, which are only for convenience of describing the present invention and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and operate, and thus, should not be construed as limiting the present invention; the terms "connected," "mounted," "secured," and the like are to be construed broadly and include, for example, fixed connections, removable connections, or integral connections; may be directly connected or indirectly connected through an intermediate. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the description herein, the description of the terms "one embodiment," "some embodiments," "specific embodiments," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.