SU1117763A2 - Device for protecting asynchronous motor against overload - Google Patents

Abstract

DEVICE FOR PROTECTION OF ASYNCHRONOUS MOTOR FROM OVERLOADING by author. St. No. 1001292, characterized in that, in order to increase reliability, the closing contact of the intermediate shunt relay is additionally inserted, connected in series with the closing contact of the maximum current relay.

Description

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Ltd. The invention relates to electrical engineering, in particular, to relay protection devices for electric motors. According to the main author. St. No. 1001292, a device for protecting an asynchronous electric motor against overload is known, which contains a magnetic starter, the coil of which is connected to the power wires through the series-connected Stop and Start buttons and opening contacts of thermal relays, the maximum current relay of which is fed into one of the power relays electric motor of wires, and shunt relay, the coil of which is connected to the network through an additional contact connected in parallel to the Start button and the closing contact of the maximum The relay is connected in parallel and the Start button is connected in parallel with the time-closing contact of the shunt relay and the breaking contact of the current relay connected in series with the closing contact of the magnetic actuator 1. A disadvantage of the known device is that with each activation of the current relay The make contacts momentarily energize the coil of the shunt relay, thereby shortening the life of the relay. In addition, if the response time of the shunt relay turns out to be long, it is possible that the electric motor will not be protected by reconnecting the coil of the magnetic starter to the network by closing contacts of the shunt relay. The purpose of the invention is to increase the reliability of the device in operation. The goal is achieved by the addition of a closing contact of the intermediate bypass relay, connected in series with the closing relay of the current relay, to the device. The drawing shows the scheme of the proposed device for protecting an asynchronous motor against overload. The device contains a magnetic starter, the winding 1 of which is through sequential ss) (DI11en11) 1e) iku 2 "Stop and the button 3" Start, bypassing the closing unit-co1pch1KT () m 4 magnetic starter, connecting to the mains, and the power contacts .5 magnetic The actuator includes 1), with the winding of the echo motor 6, the maximum current relay, which is connected via the current transformer 8 of the PC to one of the () mains supply networks. In series with the locking contact 4, parallel-connected disconnecting contact 9 of the maximum current relay and the first closing contact 10 of the bypass relay, operating with opening delay, the coil 11 of which is connected to the network through the serially connected closing contact 12 of the maximum current relay and the second closing contact 13 are connected. shunt relay 11, in parallel with which the additional closing contact 14 of the button 3 “Start. In addition, the circuit of the coil 1 of the magnetic actuator includes the breaking contacts of 15 thermal relays, the heating elements 16 of which are included in different phases of the supply network. The device works as follows. When the start button 3 is pressed, the coil I of the magnetic starter is pressed through the button 2 Stop and disconnecting contacts 15 is connected to the network. At the same time, through the auxiliary contact 14 of the Start button, the coil 11 of the shunt relay is powered. The power contacts 5 and the auxiliary contact 4 are closed and the engine 6 begins to disperse. When a starting current is triggered, the maximum current relay operates, the coil 7 of which is connected through the current transformer 8 to the mains supply phase, the contact 12 is opened in the coil 11 circuit of the bypass relay. The motor 6 will not be disconnected in this case, since the coil 1 of the magnetic starter will be powered through the closing contact 10 of the shunt relay. After the start of the electric motor 6 and the current consumed by it, the contacts 9 and 12 of the maximum current relay return to their original condition, as a result of which the shunt 11 relay is disconnected, its contact 10 with a small delay opens and the circuit is ready for operation. When the current consumed by the electric motor exceeds the permissible value, the maximum current relay opening contact 9 de-energizes the coil 1 of the magnetic starter and the electric motor 6 is disconnected from the network by contacts 5. The closing contact 10 will not work, as the shunt relay 11 coil, despite the closing contact 12 of the current relay, will be disconnected from the network by its closing contact 13 and additional contact 14 of the button 3 “Start. A small delay (of a fraction of a second) when the closing contact 10 of the shunting relay is released ensures the integrity of the power supply circuit of the coil 1 of the actuator when contacts 9 and 12 of the maximum current relay return to their initial state, this also eliminates the false triggering of the device during current run-up electric motor 6. If the electric motor is started up but by some kind of latin engine. that

the thermal relay 16 will operate, having opened the power supply circuit of the coil 1 of the starter with its contacts 15. The thermal relay also provides protection for the electric motor 6 in case of small continuous overloads when the current consumed by it is insufficient to operate the maximum current relay.

The introduction of an additional contact of the shunt relay connected in series with the closing contact of the current relay excludes short-term energizing under the coil voltage of the shunt relay when the protection is triggered, since such activation becomes possible only when the Start button in

the result is that the motor is not disconnected by protection due to the false triggering of the shunt relay.

In addition, the work of the contacts of the current relay is greatly facilitated, since the number of commutations by these contacts of the current circuits is reduced.

The proposed device can be widely used for the protection of electric motors installed on agricultural objects characterized by severe starting conditions. At the same time, the protection of the electric motors is increased.

Claims (1)

DEVICE FOR PROTECTING ASYNCHRONOUS ELECTRIC MOTOR FROM OVERLOAD by ed. St. No. 1001292, characterized in that, in order to increase reliability, an additional closing contact of the intermediate bypass relay is added, connected in series with the closing contact of the maximum current relay. SU ,,, 1117763