Faraday Predictive: Understanding the Fundamentals of Motor Current Signature Analysis

Abstract

Motor current signature analysis is a method to perform on-line moni- toring of the condition of electrical motors by examining the spectrum of the residual current of the motor for sidebands around the main frequencies. The interpretation of these spectra would be improved by having a physics based understanding of how particular perturbations appear in a spectrum. This report considers two possible models for an induction motor and its residual current. The first model considered uses the Steinmetz equivalent circuit, a stan- dard model from the literature. The second model is derived from first principles based on Faraday and Ohms law and the conservation of an- gular momentum. It is able to capture the coupling between the rotor dynamics and the residual current. Some initial results are given for each model using both asymptotic and numerical techniques. They indicate that both models can pro- duce sidebands, although the physical model captures the complicated asymmetric behaviour seen in real spectrums. The modelling in this report is a good basis that with further analysis should be able to ex- plain why particular sidebands are observed when particular defects are present.

Publication
European Study Groups with Industry ESGI 162. Leeds

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