Stator Current Demodulation Using Square Roots Current Stator for Inverter-Fed Induction Motor at Low Load Conditions

This paper presents an improved off-line method for induction machine rotor fault diagnosis at low load condition. The proposed method is based on the analysis, in the frequency domain, of the stator current amplitude modulation extracted by calculation of the root of the squared three phase currents. This method is theoretically presented and experimentally validated by testing three different induction machines: one is healthy, the second has one broken bar and the third presents two broken bars. Each motor is subjected to three load conditions (low, medium and high) and supplied by a voltage inverter operating at different frequencies. The main results are compared with these obtained by the traditional MCSA method to show that the proposed method can successfully detect the rotor fault even at low load condition which makes it more suitable then the MCSA method.