Modulation Signal Bispectrum Analysis of Motor Current Signals for Condition Monitoring of Electromechanical Systems

Abstract

Induction motor is one of the most widely used prime drivers and electric energy consuming devices in industry. Accurate and timely diagnosis of faults in motors will help to maintain their operating under optimal status and avoid excessive energy consumption and severe damages to systems. In this study, instantaneous motor current and voltage signals (IMCVS) is analyzed by an advanced Modulation Signal Bispectrum (MSB) method to achieve accurate demodulations of Frequency Modulation (FM) and Amplitude Modulation (AM) by minimizing noise influence and enhancing modulation characteristics simultaneously. Firstly, the modulation effects due to motor faults and downstream mechanical components were modelled, thus finding the interaction between AM and FM effect and hence developed a scheme to use the signature of AM and FM jointly for accurate fault diagnosis. Then experimentations were carried out to verify the performance of the proposed scheme in detecting and diagnosing common mechanical faults including Shaft Misalignments(SM), Motor Rotor Broken Bar (BRB), Stator Resistance Imbalance (SRI) and compound BRB with SRI.