The working principle of the thermal relay in the motor - News - Global IC Trade Starts Here.

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Thermal relays are protective devices used for overload protection of electric motors or other electrical equipment and electrical circuits.
The working principle of the thermal relay in the motor: In the actual operation of the motor, such as dragging the production machine to work, if the machine is abnormal or the circuit is abnormal, the motor is overloaded, the motor speed decreases, and the current in the winding increases. Large, so that the winding temperature of the motor rises. If the overload current is not large and the overload time is short, the motor winding does not exceed the allowable temperature rise. This overload is allowed. However, if the overload time is long and the overload current is large, the temperature rise of the motor winding will exceed the allowable value, which will cause the motor winding to age, shorten the service life of the motor, and even burn the motor winding in severe cases, so the overload cannot be tolerated by the motor. The thermal relay utilizes the principle of the thermal effect of the current to cut off the motor circuit in the event of an overload that the motor cannot withstand, providing a protection device for the overload protection of the motor.
The working principle of the thermal relay in the motor: When the thermal relay is used to protect the motor, the thermal element is connected in series with the stator winding of the motor, and the normally closed contact of the thermal relay is connected in series to the control circuit of the electromagnetic coil of the AC contactor, and Adjust the setting current adjustment knob so that the chevron lever is at an appropriate distance from the push rod. When the motor works normally, the current passing through the heat element is the rated current of the motor, the heat element heats up, and the bimetal is bent after being heated, so that the push rod just touches the herringbone lever, and cannot push the chevron lever. The normally closed contact is in a closed state, the AC contactor remains closed, and the motor operates normally.
The working principle of the thermal relay in the motor: If the motor is overloaded, the current in the winding increases, the current in the thermal relay element increases, the temperature of the bimetal rises higher, the bending degree increases, and the herringbone lever is pushed. The glyph pushes the normally closed contact, disconnects the contact and disconnects the AC contactor coil circuit, causes the contactor to release, cuts off the power of the motor, and the motor is stopped to be protected. It can be seen that the thermal relay usually disconnects the control circuit of the contactor directly to disconnect the main circuit.