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Thermal relay

PostTime: 2022-11-01 Views: 672

Thermal relay

Thermal relay is mainly used for overload protection of electrical equipment (mainly motor). Thermal relay is a kind of electrical appliance that works on the principle of current thermal effect. 


It has inverse time limit action characteristics similar to the motor's allowable overload characteristics. It is mainly used in conjunction with contactors to protect three-phase asynchronous motors from overload and phase failure. In the actual operation of three-phase asynchronous motors, overcurrent (overload and phase failure) phenomena caused by electrical or mechanical reasons are often encountered. If the overcurrent is not serious, the duration is short, and the winding does not exceed the allowable temperature rise, this overcurrent is allowed; 


If the over-current is serious and lasts for a long time, it will accelerate the insulation aging of the motor, or even burn the motor. Therefore, the motor protection device should be set in the motor circuit. There are many kinds of motor protection devices in common use, and bimetal thermal relay is the most widely used. The bimetallic strip thermal relay is three-phase type, with or without phase failure protection.

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