Comparison of Different Methods to Detect Static Air Gap Asymmetry in Inverter Fed Induction Machines

Monitoring of air gap asymmetry in induction machines is very challenging even considering steady state and ideal line fed operation. Considering also inverter fed and dynamic operation situation gets even worse. In this investigation two different attempts to detect static eccentricity are compared with respect to their sensitivity at different machines. The first method is based on Fourier transform of the phase currents also denoted motor current signature analysis (MCSA) in literature. The second is based on the exploitation of the transient current response of the machine to an excitation with voltage pulses caused by the inverter switching. It is shown that the performance of the MCSA depends on the number of slots per pole whereas the indicator obtained from the transient current response is not affected by this parameter.