Thermal relay is mainly used to overload protect the asynchronous motor. Its working principle is that after the overload current passes through the thermal element, the double metal sheet is bent to push the action mechanism to drive the contact action, so as to disconnect the motor control circuit and realize the motor shutdown, and play the role of overload protection.Given the long time of heat transfer required during thermal bending of bimmetal plate, the thermal relay cannot be used as short circuit protection, but only as overload protection of overload protection thermal relay.
When the thermal relay is used to overload protect the motor, connect the thermal element and the stator winding of the motor in series, the normally closed contact of the thermal relay is connected in the control circuit of the electromagnetic coil of the AC contactor, and the setting current adjustment knob is adjusted to make the herringbone lever an appropriate distance from the push rod.When the motor works normally, the current through the thermal element is the rated current of the motor. When the thermal element warms up, the double metal sheet is bent after heating, so that the push rod just contacts with the herringbone lever, but cannot push the herringbone rod.The normally closed contacts are closed, the AC contactor remains engaged, and the motor operates normally.
Post time: Jun-18-2025
