Online Detection of Rotor Eccentricity and Demagnetization Faults in PMSMs Based on Hall-Effect Field Sensor Measurements

Abstract

Rotor eccentricity and local demagnetization in permanent magnet synchronous motors (PMSMs) increase unbalanced magnetic pull and motor vibration resulting in accelerated aging of motor components. If the asymmetry in the rotor remains undetected, it can increase in severity, and increase the risk of stator-rotor contact, which causes forced outage of the motor and driven process. Detection of PMSM rotor asymmetry currently relies on offline testing and online vibration/current spectrum analysis. However, they are inconvenient or cannot provide reliable detection of rotor faults for all PMSM designs. In this paper, the feasibility of using the signals from analog Hall-effect field sensors for detecting eccentricity and local demagnetization is investigated. It is shown that Hall sensors present inmachines for motion control can be used for directly measuring the variation in the flux inside the motor due to rotor magnetic asymmetry with minimal hardware modifications. Three-dimensional finite-element analysis and experimental results performed on an interior PMSM show that the proposed method can provide sensitive and reliable detection of dynamic/mixed eccentricity and local PM demagnetization.