RU1831763C - Procedure of three-phase asynchronous motor control by switching windings from "srider" scheme to "delta" scheme and back - Google Patents

Abstract

Usage: in electric drives of general industrial mechanisms. The essence of the invention is to reduce inrush current and torque. The phase windings are switched from a star to a triangle by turning off some triacs and turning on other triacs at moments of zero voltage difference across them, connecting the phase windings to a sequence of linear voltages lagging 30 degrees apart. The phase windings are switched from a triangle to a star by switching off one triacs in turn and simultaneously switching on other triacs after 10-12 ms at the moment of zero voltage difference across the triac. The predetermined switching algorithm implements the control unit. Zero indicators control the voltage across the triacs through zero. 1 ill.

Description

The invention relates to electrical engineering and can be used to control the power consumption of an induction motor in AC electric drives of general industrial mechanisms.

The technical result of the invention is to reduce inrush currents and torque during switching, as a result, the reliability of the electric drive and the quality of voltage in the connection unit are increased.

The drawing shows a diagram of a device for implementing the proposed method.

The device comprises switches 1 and 2 for switching on phases 3-5 of the stator winding with a star and a triangle, made on triacs 6-10. In parallel to triacs 6–10, null indicators 11–15 are turned on.

Some conclusions of triacs 6 and 7 are connected to the ends of the first 3 and third 5 phase windings, respectively, and the other conclusions are interconnected and connected to the end of the second 4 phase winding. Each of triacs 8-10 is connected by a day terminal to the corresponding end of one phase winding, and the other to the corresponding beginning of the previous phase winding. One input of the control unit 16 is connected to the source of control voltages Uy, the other input to the outputs of the null indicators 11-15, and the output to the control inputs of the corresponding triacs 6-10.

The device operates as follows.

In the absence of a control signal, sistor 6-10 are turned off, phase windings 3-5 are turned off and the motor is stationary.

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Let the engine run on a star circuit, which corresponds to the on state of triacs 1-2. When a control signal is applied to switch the stator winding from the star circuit to the triangle circuit, the triac 6 is first turned off at the moment the current in it passes through zero and at the moment of zero potential difference between the end of the first 3 and the beginning of the third 5 phase windings, turn on the triac 10, connecting the first 3 phase UAC line voltage winding. Then triac 7 is turned off at the moment the current in it passes through zero and at the moment of zero potential difference between the end of the second 4 and the beginning of the first 3 phase windings, turn on the triac 8, connecting the second 4 phase winding to the line voltage UBA of the supply network. Further, at the moment of zero potential difference between the end of the third 5 and the beginning of the second 4-phase windings, the triac 9 is turned on, connecting the third 5-phase winding to the linear voltage UCB, obtaining a triangle circuit.

When the phase windings of the electric motor are switched from the triangle circuit to the star circuit, the 10,9,8 symmetrical switches are switched off alternately at the moments when the current passes through them to zero. Then, 10-12 ms after tripping the triac 10, at the moment of the zero potential difference between the ends of the first 3 and second 4 phase windings, the triac 6 and 7 simultaneously turn on, obtaining a star circuit.

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The implementation of the proposed algorithm allows one to reduce the inrush of current and moment during phase-wise switching of the star

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Claims (1)

Golnik stator winding three-phase asynchronous electric motor. SUMMARY OF THE INVENTION A method for controlling a three-phase asynchronous electric motor by switching its windings from a star circuit to a delta circuit and vice versa, in which, to switch from a star circuit to a triangular circuit, the end of the first phase is turned off 10 windings from the ends of two other phases and connect it to the beginning of the third phase of the winding, then disconnect the end of the second phase from the end of the third phase and connect to the beginning of the first phase, connect the end of the third phase 15 to the beginning of the second phase, and switching from the triangle circuit to the star circuit is carried out by alternately disconnecting the ends of the winding phases, starting with the first, and connecting them to each other, and disconnecting The 20 ends of the winding phases are carried out at the moment the current in the winding phases passes through zero, and they are connected at the moment of a zero potential difference between the end of the connected phase of the winding and the corresponding point of its connection, characterized in that when switching from a circuit a triangle to a star circuit after disconnecting the end of the first phase of the winding from the beginning of the third phase of the winding disconnects the end of the third phase from the beginning of the second phase, then the end of the second phase is disconnected from the beginning of the first phase, then connect simultaneously each other end of the winding phases at time zero raz35 the potential applied between the ends of the first and second phase windings 10-12 msec after turning off the end of the first phase winding from the start of the third phase. "WITH 25