A device for controlling a single-phase asynchronous electric motor. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Electric motors

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The proposed device can be used to control single-phase asynchronous motors, in particular, for starting and braking an asynchronous motor (AM) with a low power squirrel-cage rotor, having a starting winding or starting capacitor that is disconnected before the end of the start. It is possible to use the device for starting more powerful IM, as well as for starting three-phase motors operating in single-phase mode.

In the known device [1], a repeated normal start is possible only after the thermistor has cooled down and the braking mode of the robot is not provided. The proposed device has wider functionality.

The device (Fig. 1) contains a two-pole switch SA1 with two positions, with the help of which the working winding P of the asynchronous motor and the winding of the electromagnetic relay K1 are connected to the terminals of the supply network through the rectifier diode VD1, a timing RC circuit consisting of parallel-connected resistor R1 and an electrolytic capacitor C1. Closing contact K1.1 of relay K1 is used to connect the starting winding P AD to the mains through the phase-shifting element C2 and switch SA1.

In the initial pre-start position, the winding of the electromagnetic relay K1 and the rectifier diode VD1 are shunted by the contacts of the SA1 switch. The timing RC circuit is connected through the same switch contacts to the terminals of the working winding P.

The device works as follows.

When the HELL is turned on with the help of a two-pole switch SA1, the working winding R flows around and relay K1 is activated along the circuit: diode VD1, timing RC circuit, relay winding K1, switch SA1. Relay K1 with contact K1.1 connects to the network the starting winding P with phase-shifting element C2. After a period of time determined by the time-setting RC chain, the VD1 diode is locked by this chain and the relay opens its contact K1.1 in the circuit of the starting winding P, disconnecting it from the network. The start of the AD is completed.

Capacitor C1 during the entire time of operation of the IM is in a charged state, almost up to the amplitude value of the mains voltage. The voltage across it can be somewhat reduced by reducing the value of the resistor R1. When the HELL is disconnected from the network, the VD1 diode and the working winding P of the engine are shunted by the SA1 switch, and the timing RC chain is connected through the switch to the working winding terminals. The capacitor of the timing RC circuit is discharged to the working winding P, creating a braking torque on the IM shaft. Restart is possible immediately after stopping the blood pressure, because. the RC capacitor is discharged. IM deceleration time up to 1 s with free run-out of the IM rotor up to 10 s.

A simplified version of the device is shown in Fig.2. This option was used by the author for several years for the IM of the refrigeration unit of the refrigerator, which had a "burnt" starting winding due to a large excess voltage in the network, as a result of which the starting relay of the refrigerator did not turn off the starting winding of the IM and it overheated. braking (contacts 2-3 of the SA1 switch) was not used due to uselessness, and contacts 1-2 were replaced by refrigerator thermal relay contacts.

Details. As a switch SA1, any toggle switch suitable for current and voltage is used. Diode VD1 type D226B can be replaced by D237B, D237V or KD105 with any letter index. Resistor R1 type MLT-2 50 ... 100 kOhm.

Capacitor C1 - electrolytic type KE-2 for 30 microfarads and 450 V can be replaced by KE-1 or EM. The last one is small. Electromagnetic relay K1 intermediate relay of alternating current for 220 V type RP-21, RP-25 or MKU-48. Capacitor C2 is selected at the rate of 7 μF per 100 W of power of the MBGO-2 type IM for a voltage of at least 400 V or the MBGCH type, which is preferable.

The device does not consume electricity during the operation of the AD, does not require adjustment and starts working immediately with serviceable elements and proper installation.

References:

1. Japan Patent No. 14058, class 55A342,1969, XNUMX.
2. Auth. certificate USSR No. 629616, class NO2P1/42.

Author: K.V. Kolomoitsev

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