Detection of Radial and Axial Magnet Defects in PM Synchronous Motors

This paper presents a novel method for the detection of magnet cracks or defects through analysis of back electromotive force (EMF) voltage, line current and vibration signals for radial flux permanent magnet (PM) synchronous motors. An integer slot PM motor with 12 poles is used in the study. Different types of faults including both radial and axial magnet crack defects are studied in detail. Random forest based magnet defect detection is utilized and a classification scheme is proposed in order to analyze the changes in the harmonics arising from radial or axial magnet defects. The results clearly show that the harmonics is altered in such a manner that it is possible to determine not only the magnet fault but the type of the magnet defect using motor voltage, current or vibration data.

I. Introduction

THE usage of permanent magnet (PM) synchronous motors instead of AC induction motors have been increased during last decades owing to its high torque density, efficiency, torque-per-ampere and torque-per-weight ratios capabilities [1]-[2]. Although PM motors require less maintenance, fault diagnosis systems should also be installed to observe their performance during the life cycle.