Thermal relay, electrical protection God

Update date:2018-05-07 Source:MAXGE

Thermal relay is the abbreviation of thermal overload relay. It is a kind of protective electrical appliance that uses the thermal effect of current to cut off the circuit. It is often used in conjunction with a contactor. The thermal relay has the advantages of simple structure, small size, low price and good protection performance. Widely used by people, it is mainly used for motor overload protection, phase failure and current unbalanced operation and other electrical equipment heating state control.

Thermal relay

There are usually a pair of normally open points and a pair of normally closed points, the upper and lower ports on both sides of the wiring, the setting value (current) adjustment knob, reset button and other components.

The choice of thermal relay: whether the choice of thermal relay is right, directly affects the reliability of motor overload protection. In general, it should be considered comprehensively according to the type of motor, working environment, starting conditions and load conditions.

Thermal relay

(1) In principle, the rated maximum current of the thermal relay is generally slightly larger than the rated current of the motor. After the thermal relay is selected, the adjusting knob of the thermal relay is adjusted to be equal to the current value of the motor according to the rated current of the motor.

For motors with poor overload capability, the rated current of the thermal relay should be appropriately small, and the setting current should be adjusted to 60% - 80% of the rated motor current. When the motor starts with a load and the starting time is long or the load of the motor is an impact load (such as a punch press, etc.), the setting current of the thermal relay should be greater than the rated current of the motor.

Thermal relay

(2) The difference between the operating temperature of the thermal relay and the ambient temperature of the protected electrical equipment should not exceed 15-25 degrees.


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