Working principle and scope of application of thermal overload relay

Publish Time:2019-07-05 Author:admin Views:0

The thermal components of the thermal overload relay are connected to the motor circuit either directly or via a current transformer. When the motor is overloaded, the main bimetal is heated to the operating temperature, causing the relay to act, breaking the power circuit of the motor and protecting the motor from overload. The operation time of the thermal overload relay and the magnitude of the overload current vary according to the inverse time limit. Therefore, the thermal characteristics are easily matched with the thermal characteristics of the motor, and the structure is simple, the price is low, the operation performance is stable, and the use is convenient. Therefore, most squirrel-cage rotor motors and partially wound rotor motors in the 1990s still used thermal overload relays for protection against overload, phase failure, and current imbalance. The thermal overload relay can also be used as a control device for the heating state of other electrical equipment.

Scope of application

The scope of application of thermal overload relay: thermal overload relay is used for AC 50Hz, rated insulation voltage 660V, current 0.1～630A, mainly used for overload and phase failure protection of three-phase AC motor. The starter can be combined with an adapted AC contactor, such as an outline thermal relay profile.