Stator fault detection in induction machines using triplen harmonics at motor terminal voltage after switch-off

Almost 30-40% portion of all reported induction machine faults are stator faults related. In fact, going by the number of occurrences, the position of stator faults is only second to bearing related faults. Third harmonic line currents have been reported to increase under stator fault conditions. It has been shown in this paper that they are primarily due to the interaction of saturation caused permeance wave and reverse rotating field caused due to stator faults or voltage unbalance and machine structural imbalance (usually small). Thus, voltage unbalance cannot be distinguished from stator faults. The third and the other triplen related harmonics are however found to be a very decisive indicator of the fault, if measured in the machine terminal voltages just after switch-off. The fault detection technique is independent of machine parameters and supply unbalances. Simulation as well as experimental results are presented with very few shorted turns.