A New Method to Discern Mechanical Unbalances from Rotor Faults in Induction Machines

Intensive researches have been spent with the aim of separating load torque unbalance and rotor faults effects in induction machines by devoted diagnostic procedures. Recently, current space vector active and reactive components due to these troubles are considered for their different relevance in correspondence of the two events: the torque unbalance seems to affect more the active component than the reactive one, vice versa the rotor faults. In this paper it is shown that the space vector components amplitude and their phase displacement must be considered, being the latter the main parameter: if the active component leads or lags the reactive one by less than π/2 a rotor fault is present, otherwise a torque unbalance is present. Regarding the components amplitude, it depends, overall, besides on trouble severity, on the operating conditions and on the combined rotor-load inertia.