The electromagnetic interference and diagnosis of rotor fault for inverter fed motor

In inverter fed motor speed control systems, the electromagnetism interferes, which are caused by the high speed switching of the inverter, bring bad effects for measuring the current of the induction motor stator. In this paper, the complexity and specialty of measuring the stator current for the self-commutated inverter fed motor are studied, some experiments are carried out. As results, effective ways to reduce the interfere of the measuring circuit are provided; the on-line fault diagnosis for the induction motor broken rotor bars which run under different situations are realized, by employment of fast Fourier transform (FFT) and time-varying frequency spectrum analysis.