Demodulation analysis for exact rotor faults detection under changing parameters

Demodulation techniques extract modulating currents induced by induction motors rotor faults and directly evaluate these fault currents in time and frequency domain. Vector representation of amplitude and phase modulation is analyzed with the investigation, how both modulations change with changing parameters. It is proved that fault indicators of amplitude modulation do not change with motor changing parameters and they are the base of rotor faults detection. Two demodulation methods based on complex analytical signal are presented. Experiments were focused to IM energized from line and inverters.