CN104967362A - A kind of control circuit used for motor step-down start - Google Patents

Abstract

The invention provides a control circuit for starting a motor with reduced voltage, belonging to the technical field of motors. It solves the technical problems such as the low application range of the control circuit for the step-down starting of the motor, the voltage loss of the motor at the moment of voltage switching, and the like. The control circuit includes a motor starting contactor KM1, a transformer, a relay KA1, a relay KA2, a relay KA3, a relay KA4, a relay KA5, a relay KA6 and a motor M. The invention utilizes the principle of electromagnetic induction to combine traditional transformer switching tap voltage regulation with compensation voltage regulation, and adjusts the compensation voltage by changing the turns ratio of the primary and secondary coils of the transformer, thereby adjusting the output voltage to achieve the purpose of step-down start-up , and eliminate the problem of motor voltage loss at the moment of voltage switching.

Description

A kind of control circuit used for motor step-down start

technical field

The invention belongs to the technical field of electric motors, and relates to a control circuit for starting electric motors with reduced voltage.

Background technique

The starting current of the motor is approximately proportional to the voltage of the stator, so it is necessary to reduce the stator voltage to limit the starting current, that is, step-down starting; step-down starting is more common in small and medium power motors, and the current common step-down starting method is star-delta starting And autotransformer step-down starting, the former can be used for frequent starting but the starting torque is low, not suitable for heavy-load starting, the latter has high starting torque, can be heavy-load starting but cannot start frequently; at the same time, both of them have The torque impact is large, and the motor loses voltage at the moment of voltage switching.

Therefore, those skilled in the art are devoting themselves to developing a control circuit that has a wide range of applications and eliminates the problem of voltage loss of the motor at the moment of voltage switching.

Contents of the invention

The present invention aims at the above-mentioned problems existing in the existing technology, and provides a control circuit for motor step-down startup. The technical problem to be solved by the present invention is: how to eliminate the problem of voltage loss of the motor at the moment of voltage switching.

The purpose of the present invention can be achieved through the following technical solutions:

A control circuit for motor step-down starting, characterized in that the control circuit includes a motor starting contactor KM1, a transformer, a relay KA1, a relay KA2, a relay KA3, a relay KA4, a relay KA5, a relay KA6 and a motor M, The motor starting contactor KM1 is electrically connected to a three-phase power supply and a transformer respectively, and the transformer includes a secondary coil N1, a primary coil N2 and a primary coil N3; one end of the relay KA1 is electrically connected to the three-phase power supply, so The other end of the relay KA1 is electrically connected to the upper end of the primary coil N2; one end of the relay KA2 is electrically connected to the three-phase power supply, and the other end of the relay KA2 is respectively connected to the lower end of the primary coil N2 and the One end of the relay KA4 is electrically connected; one end of the relay KA3 is electrically connected to the three-phase power supply, and the other end of the relay KA3 is electrically connected to one end of the relay KA4; the other end of the relay KA4 is electrically connected to the three-phase power supply. The upper end of the primary coil N3 is electrically connected; the relay KA5 and the relay KA6 are connected in parallel and one end of the relay KA5 is electrically connected to the three-phase power supply, and the other end of the relay KA5 is electrically connected to the lower end of the primary coil N3. Connection; the upper end of the secondary coil N1 is electrically connected to the motor starting contactor KM1, and the lower end of the secondary coil N1 is electrically connected to the motor M.

In the above-mentioned control circuit for motor step-down starting, the secondary coil N1 includes a first secondary coil, a second secondary coil, and a third secondary coil, and the primary coil N2 includes a first primary Coil, the second primary coil and the third primary coil, the primary coil N3 includes the fourth primary coil, the fifth primary coil and the sixth primary coil, the first secondary coil, the first primary coil and the fourth primary coil A transformer circuit is formed, the second secondary coil, the second primary coil and the fifth primary coil constitute a transformer circuit, and the third secondary coil, the third primary coil and the sixth primary coil constitute a transformer circuit line.

In the above-mentioned control circuit for step-down starting of a motor, the first secondary coil is electrically connected to the C-phase of the three-phase power supply, and the second secondary coil is electrically connected to the B-phase of the three-phase power supply, The third secondary coil is electrically connected to phase A of the three-phase power supply.

In the aforementioned control circuit for step-down starting of a motor, the first primary coil is electrically connected to phase C of the three-phase power supply, the second primary coil is electrically connected to phase B of the three-phase power supply, and the The third primary coil is electrically connected to phase A of the three-phase power supply.

In the aforementioned control circuit for step-down starting of a motor, the fourth primary coil is electrically connected to phase C of the three-phase power supply, the fifth primary coil is electrically connected to phase B of the three-phase power supply, and the The sixth primary coil is electrically connected to phase A of the three-phase power supply.

The beneficial technical effects of the present invention are: using the principle of electromagnetic induction, combining the traditional transformer switching tap voltage regulation with compensation type voltage regulation, and adjusting the compensation voltage by changing the turns ratio of the primary and secondary coils of the transformer, thereby adjusting the output voltage, The purpose of step-down starting is achieved, and the problem of voltage loss of the motor at the moment of voltage switching is eliminated.

The idea, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings, so as to fully understand the purpose, features and effects of the present invention.

Description of drawings

FIG. 1 is a circuit diagram of a control circuit for starting a motor with reduced voltage provided by the present invention.

As shown in the figure: 11-the first secondary coil, 12-the second secondary coil, 13-the third secondary coil, 21-the first primary coil, 22-the second primary coil, 23-the third primary coil, 31 - fourth primary coil, 32 - fifth primary coil, 33 - sixth primary coil.

Detailed ways

In order to understand the technical solution of the present invention more intuitively and completely, the non-limiting feature descriptions in conjunction with the embodiments of the present invention and the accompanying drawings are as follows:

As shown in Figure 1, the control circuit includes a motor starting contactor KM1, a transformer, a relay KA1, a relay KA2, a relay KA3, a relay KA4, a relay KA5, a relay KA6 and a motor M, where the motor M is a three-phase AC motor, and the motor starts The contactor KM1 is respectively electrically connected to the three-phase power supply and the transformer, and the transformer includes a secondary coil N1, a primary coil N2 and a primary coil N3.

As shown in Figure 1, one end of the relay KA1 is electrically connected to the three-phase power supply, and the other end of the relay KA1 is electrically connected to the upper end of the primary coil N2; one end of the relay KA2 is electrically connected to the three-phase power supply, and the other end of the relay KA2 is respectively connected to the primary coil N2. The lower end of the coil N2 is electrically connected to one end of the relay KA4; one end of the relay KA3 is electrically connected to the three-phase power supply, the other end of the relay KA3 is electrically connected to one end of the relay KA4; the other end of the relay KA4 is electrically connected to the upper end of the primary coil N3; Relay KA5 and relay KA6 are connected in parallel and one end of relay KA5 is electrically connected to the three-phase power supply, the other end of relay KA5 is electrically connected to the lower end of the primary coil N3; the upper end of the secondary coil N1 is electrically connected to the motor starting contactor KM1, and the secondary coil The lower end of N1 is electrically connected to the motor M.

Further, the secondary coil N1 includes the first secondary coil 11, the second secondary coil 12 and the third secondary coil 13, and the primary coil N2 includes the first primary coil 21, the second primary coil 22 and the third primary coil 23 , the primary coil N3 includes a fourth primary coil 31, a fifth primary coil 32 and a sixth primary coil 33, the first secondary coil 11, the first primary coil 21 and the fourth primary coil 31 constitute a transformer circuit, and the second The primary coil 12 , the second primary coil 22 and the fifth primary coil 32 form a transformer circuit, and the third secondary coil 13 , the third primary coil 23 and the sixth primary coil 33 form a transformer circuit.

Further, the first secondary coil 11 is electrically connected to phase C of the three-phase power supply, the second secondary coil 12 is electrically connected to phase B of the three-phase power supply, and the third secondary coil 13 is electrically connected to phase A of the three-phase power supply .

Further, the first primary coil 21 is electrically connected to phase C of the three-phase power supply, the second primary coil 22 is electrically connected to phase B of the three-phase power supply, and the third primary coil 23 is electrically connected to phase A of the three-phase power supply.

Further, the fourth primary coil 31 is electrically connected to phase C of the three-phase power supply, the fifth primary coil 32 is electrically connected to phase B of the three-phase power supply, and the sixth primary coil 33 is electrically connected to phase A of the three-phase power supply.

This control circuit uses the principle of electromagnetic induction to combine the traditional transformer switching tap voltage regulation with compensation voltage regulation. By changing the turns ratio of the primary and secondary coils of the transformer, the compensation voltage is adjusted, thereby adjusting the output voltage to achieve step-down startup. Purpose: This control circuit takes into account the advantages of the existing step-down starting method, and eliminates the problem of the motor losing voltage at the moment of voltage switching. At the same time, it adopts a step-by-step step-up method to start, reducing the torque impact when starting. , which is conducive to the reliable operation of the motor. The invention is not affected by frequent starting and load conditions, and under the same load conditions, the space required by the circuit used in the invention is smaller and the operation is more reliable.

The working process of this control circuit is as follows: When relay KA1 and relay KA2 are closed and other relays are disconnected, the system outputs the lowest voltage. If relay KM1 is closed at this time, the motor M starts with the lowest voltage; KA4 and relay KA5 are closed, and the other relays are disconnected, the output voltage of the system will increase by one gear, and the torque of the motor M will increase. It is also possible to close the relay KM1 at this time, and the motor will start with a higher torque; after a period of time, the relay KA1, relay KA4, and relay KA6 are closed, and other relays are disconnected. At this time, the motor operates at 380V normal pressure, and the starting process ends.

The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make many modifications and changes according to the concept of the present invention without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art shall be within the scope of protection defined by the claims.

Claims (5)

1. A control circuit for motor step-down starting, characterized in that, the control circuit includes a motor starting contactor KM1, a transformer, a relay KA1, a relay KA2, a relay KA3, a relay KA4, a relay KA5, a relay KA6 and a motor M, the motor starting contactor KM1 is electrically connected to a three-phase power supply and a transformer respectively, and the transformer includes a secondary coil N1, a primary coil N2 and a primary coil N3; one end of the relay KA1 is electrically connected to the three-phase power supply , the other end of the relay KA1 is electrically connected to the upper end of the primary coil N2; one end of the relay KA2 is electrically connected to the three-phase power supply, and the other end of the relay KA2 is respectively connected to the lower end of the primary coil N2 It is electrically connected to one end of the relay KA4; one end of the relay KA3 is electrically connected to the three-phase power supply, and the other end of the relay KA3 is electrically connected to one end of the relay KA4; the other end of the relay KA4 is electrically connected to the three-phase power supply. The upper end of the primary coil N3 is electrically connected; the relay KA5 and the relay KA6 are connected in parallel and one end of the relay KA5 is electrically connected to the three-phase power supply, and the other end of the relay KA5 is connected to the primary coil N3. The lower end is electrically connected; the upper end of the secondary coil N1 is electrically connected to the motor starting contactor KM1, and the lower end of the secondary coil N1 is electrically connected to the motor M. 2. A control circuit for motor step-down startup according to claim 1, wherein the secondary coil N1 comprises a first secondary coil, a second secondary coil and a third secondary coil, The primary coil N2 includes a first primary coil, a second primary coil, and a third primary coil, and the primary coil N3 includes a fourth primary coil, a fifth primary coil, and a sixth primary coil, and the first secondary coil, The first primary coil and the fourth primary coil form a transformation circuit, the second secondary coil, the second primary coil and the fifth primary coil form a transformation circuit, the third secondary coil, the third primary coil and the sixth primary coil form a transformer circuit. 3. A control circuit for motor step-down startup according to claim 2, wherein the first secondary coil is electrically connected to the C phase of the three-phase power supply, and the second secondary coil is connected to the phase C of the three-phase power supply. Phase B of the three-phase power supply is electrically connected, and the third secondary coil is electrically connected to phase A of the three-phase power supply. 4. A control circuit for motor step-down startup according to claim 2 or 3, wherein the first primary coil is electrically connected to phase C of a three-phase power supply, and the second primary coil is electrically connected to phase C of a three-phase power supply. Phase B of the three-phase power supply is electrically connected, and the third primary coil is electrically connected to phase A of the three-phase power supply. 5. A control circuit for step-down starting of a motor according to claim 2 or 3, wherein the fourth primary coil is electrically connected to phase C of a three-phase power supply, and the fifth primary coil is electrically connected to phase C of a three-phase power supply. Phase B of the three-phase power supply is electrically connected, and the sixth primary coil is electrically connected to phase A of the three-phase power supply.