Condition monitoring of rotor faults in induction motors by injection of low frequency signals into the supply

Nowadays most modern drive motors tend to be squirrel-cage induction motors because of their superior `power to weight´ ratio. Hence most industrial motors are practically maintenance-free because of the absence of commutators and slip rings. There is, however, a danger that the electrical engineers are taking those motors too much for granted. Indeed, induction motors can only be very reliable if proper attentions are given. Moreover, it is well known that unexpected failures in such drives could result in many unpleasant situations. Coupled with the fact that the cost of testing these motors periodically is only a small fraction of the total maintenance cost in a drive system, any responsible electrical engineer should introduce a well planned condition monitoring schedule to maximum the reliability of their induction motor drives