Comparison of results for eccentric cage induction motor using Finite Element method and Modified Winding Function Approach

Air-gap eccentricity is a fault that mainly affects large induction motors. In the worst case an eccentricity fault can result in a stator rotor rub thereby causing severe damage to the motor. As a result eccentricity fault detection has gained considerable significance. Of all detection schemes for this fault, Motor Current Signature Analysis (MCSA) is the most widely used technique. This scheme relies on identifying fault specific frequency component in the line current spectrum of the motor to identify the type of fault. The severity of the fault can be estimated by monitoring the magnitude of the characteristic frequency component. To characterize the fault severity an accurate model of induction motor has to be developed. Two models - Finite Element(FE) based model and Modified Winding Function Approach (MWFA) based model are used in this paper to estimate the magnitude of fault specific frequency components for different eccentricities at full load condition. The results obtained from the two methods are compared to find the suitability of MWFA based model in characterizing the fault severity.