Motor control device. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Motor control device. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Electric motors

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The article describes a simple device for starting a single-phase asynchronous motor with a squirrel-cage rotor, which provides automatic shutdown of its starting winding at the end of the starting process. At the same time, the device effectively brakes the engine when it is disconnected from the mains.

A control device for a single-phase asynchronous electric motor (IM) is known, which provides starting and braking of the latter [1]. The device contains a two-pole switch for two positions, with the help of some contacts of which the working winding of the IM is connected to the network, and with the help of others - the winding of the electromagnetic relay through a timing chain and a rectifier diode. The closing contacts of the relay ensure the connection of the starting winding of the IM to the network through a phase-shifting element and a switch in the circuit of the working winding. An additional rectifier diode, a shunt switch in the circuit of the working winding of the IM, serves to power the motor windings with the rectified mains current through the closing relay contacts when the IM is disconnected from the network by the switch. However, such a device is relatively complex due to the presence of two diodes with a low utilization factor.

The figure shows a single-phase IM control circuit that does not have the indicated disadvantage.

The proposed technical solution is protected by copyright [2]. The device contains a bipolar switch SA1 for two positions, with the help of contacts 1-2 of which the working winding P of the engine is connected to the network, and contacts 3-4 - the winding of the electromagnetic relay K1 through the rectifier diode VD and resistor R. Capacitor C1 is connected to the terminals of the electromagnetic relay. Opening contacts K1.1 of the electromagnetic relay provide the connection of the starting winding P of the motor to the network through the phase-shifting capacitor C2 and contacts 1-2 of the SA1 switch. The rectifier diode VD during the operation of the AD serves to power the winding of the relay K1 with the rectified current of the network.

When the AD is turned off, the VD diode provides power to the windings R and P of the motor with a rectified mains current through the closing contacts K1.2 of the K1 relay and contacts 3-5 of the SA1 switch. In the initial pre-start position, the winding of the relay K1 is not flowed around, the contacts K1.1 of the relay are closed, and the contacts K1.2 are open.

The device works as follows. When the HELL is turned on with the help of a two-pole switch SA1, the working winding P and the starting winding P are flowed through the phase-shifting capacitor C2 and closed contacts K 1.1 of relay K.1. The engine starts. At the same time, a series chain of diode VD, contacts 3-4 of switch SA1, resistor R and capacitor C1 are flowing with current. Capacitor C1 is charged and the current flowing through it decreases, while the current flowing through the coil of relay K1 increases. At a certain current of the relay winding, it operates and opens its contacts K1.1 in the circuit of the starting winding P, disconnecting it from the network, and closes the contacts K1.2 in the SA1 switch circuit. BP start is over.

During the entire time of operation of the IM, contacts K. 1.1 are open, and contacts K1.2 of relay K1 are closed due to the presence of a charged capacitor C1 and feeding it through the diode VD.

Author: K.V. Kolomoitsev

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