Effect of unbalanced supply on dynamic eccentricity fault diagnosis in induction motor

In this paper, a precise approach is proposed to detect DE in induction motors under unbalanced voltages. To achieve this goal, one essential problem is dealt with: The frequencies of the components caused by the DE in the stator current spectrum are similar to some of the frequencies introduced by the unbalanced voltages. Thus, the present paper attempts to explain, analytically, experimentally and by simulation, the generation process of all frequency components that are a function of the unbalanced voltages and the DE. For that reason, a detailed analytical study for three-phase induction motor working with DE is performed. First, an analytical expression for the mutual inductances between stator phases and rotor loops under DE is derived using mixture of winding function and Fourier series approach. Then, both theoretical and simulation studies are presented in order to show how the stator current is influenced by the simultaneous presence of DE eccentricity and unbalance supply voltages. Finally, experimental results have been presented to validate the analytical and simulation results.