SU783905A2 - Device for protecting three-phase induction electric motor from voltage disappearance in one of supply phase - Google Patents

Description

(54) DEVICE FOR PROTECTION OF THREE-PHASE ASYNCHRONOUS

ELECTRIC MOTOR FROM DISAPPEARANCE OF YAPRIZHENI

IN ONE OF THE PHASE OF POWER

one

The invention relates to the field of electrical engineering and is intended to ensure uninterrupted operation of three-phase electric motors when the voltage disappears in one of the phases of the power supply 5, for example, in refrigeration units, and is an improvement of the known device according to ed. St. No. 595824.

The device for protection of a three-phase tO asynchronous electric motor against the disappearance of voltage in one of the supply phases contains three current instant-acting relays connected to different phases with opening contacts installed in the phases feeding the motor. In this case, between all three phases of the engine are connected chains of series-connected capacitors and open contacts of current relays.

The disadvantage of the device is a malfunction in the automatic mode, for example, with a thermostat. 25

The aim of the invention is to expand the functionality of the device by ensuring uninterrupted operation in the on / off cycle, namely, starting engine pos-30

Leaving the thermostat's contacts (i.e., the ability to turn on the engine after a short stop at the missing phase).

To achieve this goal, the device for protection of a three-phase asynchronous electric motor against the disappearance of voltage in one of the supply phases is additionally equipped with three starting capacitors and three voltage relays, each of which is connected in parallel with a working capacitor, to which the starting relay is connected capacitor.

In the drawing, the circuit diagram of the device described is given.

The device for protection of a three-phase asynchronous electric motor contains a three-phase network with three terminals 1-3, three current relays 4-6 of instantaneous action with opening contactsMy 7-9, three chains, one of which consists of an open contact 7, a relay 4 and a capacitor 10, the second one is from disconnecting contact B, relay 5 and capacitor 11, and a third from disconnecting contact 9, relay 6 and capacitor 12. Three pins 13-15 are used to connect a three-phase asynchronous electric motor 16. In this case, the device contains three relays three launchers condensate 20-22.

The device works as follows.

When one of the phases is disconnected, for example, the first before the start of the electric motor, the winding of the magnetic starter is de-energized, since the thermostat contacts are open.

When the thermostat contacts close, the starter turns on and the motor is supplied with power, to the second and third terminals. Relays 5 and 6 are turned on and their contacts open the chains. The power supply windings of the Voltage relay and the corresponding capacitors, and the relay 4 remains both exact, therefore, the contact 7 is open, as a result of which the winding of the relay 17 and the starting capacitor 20 are connected in parallel with the condensate, switch 10 . The engine starts to work after engine acceleration, falling for the same 7

Neither the capacitor 10 increases the relay 19 is turned on, and the start capacitor is switched off via contact 23

 W to

Thus, the proposed device ensures uninterrupted operation of the electric motor when the voltage disappears in one of the phases of the mains supply.

Claims (1)

Invention Formula The device for protection of the asynchronous motor against the disappearance of the voltage in one of the phases of the power supply according to the author. No. 595824, distinguished by the fact that, in order to expand its functionality, it is additionally equipped with three starting capacitors and three relays, a bucket each, of which is connected in parallel to the working capacitor, to which a voltage relay is connected starting capacitor.