Discriminating between rotor asymmetries and time-varying loads in three-phase induction motors

This paper deals with the use of the synchronous reference frame current Park's Vector in the diagnosis of rotor faults in three-phase induction motors, under the presence of time-varying loads. The effects produced by different kinds of time-varying loads are evaluated, stressing its implications in the diagnosis of rotor faults. It is shown that it is possible to discriminate the effects produced by a motor load torque oscillation from the ones introduced by the presence of a rotor asymmetry. Simulation results show that when the motor has a rotor fault and is coupled to a time-varying load, it is still possible to detect the fault. On-site tests conducted in a cement-mill corroborate the results obtained by simulation.