OVERLOAD PROTECTIVE DEVICE

PURPOSE:To detect the overload of a motor properly at all times, by providing a current correction section to correct the motor current detected by a current detection section based on the applied voltage, capacity and load factor of the motor in between the current detection section and a comparison section to compare the motor current detected by this current detection section with the reference value. CONSTITUTION:When a motor is driven, its motor current is detected by a current detection section 1. The output voltage E1 corresponding to the detected motor current is inputted into a current correction section 11. The current correction section 11 then reads out the motor current and the capacity of motor MP, finds the load factor ML of motor, inputs the applied voltage MV and capacity MP into a memory 7 to read the current correction rate I and performs the operation of current correction. After that, the output voltage E2 of the current correction section 11 corresponding to this corrected current is inputted to an input terminal 2a of a comparison section 2. No false detection of motor overload will thereby be made and the overload of motor can be detected with high precision.