The use of line current as a condition monitoring tool for three phase induction motors

Line current has become the favoured parameter for the purpose of detecting rotor faults in squirrel-cage induction motors and is being used increasingly as a basis on which to monitor the occurrence of stator insulation damage. Line current can be monitored noninvasively via clip-on current transducers; hence no interruption to the machine operation is required and the system can be made versatile and portable. Recent work has seen the development of a technique to monitor the current of the motor while under transient conditions during start-up. The author discusses how this can, under certain conditions, offer distinct advantages over steady-state monitoring