Effects of broken bars/end-ring connectors and airgap eccentricities on ohmic and core losses of induction motors in ASD's using a coupled finite element-state space method

In this paper, effects of rotor abnormalities such as broken squirrel-cage bars, broken cage connectors and airgap eccentricity on ohmic and core loss es of induction motors are presented. In this investigation, a comprehensiv e Time-Stepping Coupled Finite Element-State Space (TSCFE-SS) model was ful ly utilized here to compute the time-domain elemental flux density waveform s and various time-domain wa reforms of motor winding currents useful for c ore loss and ohmic loss computations, Such investigation is feasible by use of the TSCFE-SS model due to its intrinsic nature and characteristics, The results obtained from the simulations of an example 1.2-hp induction motor clearly indicate that faults due to broken squirrel-cage bars/end-connecto rs can increase motor core losses in comparison to the healthy case. The re sults also give the effect of saturation on the core loss distributions wit hin the cross-section of the motor, and indicate the potential for possible excessive loss concentrations and consequent hot spots near zones of bar a nd connector breakages in the rotor.