If the thermal relay is connected in series with the three-phase motor, then its role is when the motor overload occurs when the motor will appear temperature rise phenomenon, the final motor burned. After the thermal relay is connected in series, the opening and closing of the thermal relay is in the control circuit, thereby controlling the power off of the motor or (after resetting) the power supply (protection motor)
Thermal relays are generally protected as follows: the motor is in operation, often due to overload, under voltage operation, frequent start, etc., which lead to winding temperature is too high, thus shortening or burn the motor, it must use thermal relay as overheating protection. As the phase-breaking operation is the main reason for the motor burned, so the relay must also have a phase protection
Protect the main circuit current does not exceed the set value. For example: 3KW motor can use the set value of 6A thermal relay, the protection of the motor will not be burned for a long time overload.
