Performance analysis of a three-phase induction motor under mixed eccentricity condition

A substantial proportion of induction motor faults are eccentricity related. In practice, static and dynamic eccentricities happen to exist together. With this point in mind, an analytical approach to evaluate the performance of a three-phase induction motor under mixed eccentric conditions is presented in this paper. A clear and step-by-step theoretical analysis, explaining completely the presence of certain harmonics in the line-current spectrum in the presence of eccentricity, is discussed. More importantly, it is shown for the first time that a link exists between the low- and high-frequency elements of these harmonics. It is also shown that these high-frequency components are not very strong in all types of machine. These results will be useful in generating rules and laws to formulate online tools for machine condition monitoring. Finite-element results to substantiate the inductance values used in the simulation are also included. The analysis is validated by the line-current spectrum of the eccentric machine obtained through simulation using the modified winding-function approach (MWFA) and experimentation.