MONITORING OF DEFECTS IN INDUCTION-MOTORS THROUGH AIR-GAP TORQUE OBSERVATION

This paper suggests a method to monitor defects such as cracked rotor bars and the shorted stator coils in induction motors. Air-gap torque can be calculated white the motor is running, No special down time for measurement is required, Data of the air-gap torque for a motor shoul d be periodically kept for comparison purposes, Since more data than j ust a line current are taken, this method offers other potential possi bilities that cannot be handled by examining only a line current. The theoretical foundation for this proposed method is presented. Experime nts conducted on a 5-hp motor show the validity and potential of this approach, Further studies are planned to extend the proposed method in detail and to monitor defects developed in other types of rotating ma chines.