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 losses of induction motors are presented. In this investigation, a comprehensive Time-Stepping Coupled Finite Element-State Space (TSCFE-SS) model was fully utilized here to compute the time-domain elemental flux density waveforms and various time-domain wa reforms of motor winding currents useful for core 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-connectors can increase motor core losses in comparison to the healthy case. The results also give the effect of saturation on the core loss distributions within the cross-section of the motor, and indicate the potential for possible excessive loss concentrations and consequent hot spots near zones of bar and connector breakages in the rotor.