Thermal relay as more common overload protection device in dc motor controller, it usually has what effect? Let's look at. When the motor working current is rated current of the motor winding temperature rise is rated temperature rise, so thermal relay action; But when the current is small, thermal relay in after a long time will have action; And when the current is too large, the thermal relay is in short time there will be action. All in all, thermal relay is overload protection device in dc motor controller, it can reduce the overload situation.