Eccentricity fault detection in surface-mounted permanent magnet synchronous motors by analytical prediction, FEM evaluation, and experimental magnetic sensing of the stray flux density

Abstract

The paper discusses the impact of rotor eccentricity in permanent magnet synchronous motors (PMSMs), which leads to increased motor vibration and unbalanced magnetic pull, resulting in accelerated aging of motor parts. Undetected eccentricity in the motor can exacerbate these issues and lead to a higher risk of stator-rotor contact and forced outages. The study proposes a technique for detecting eccentricity faults using an analog magnetic field sensor outside the motor, without requiring the sensor to be installed within the motor. The proposed technique was evaluated using analytical calculations, 2-D finite elements, and experimental results. The proposed method was evaluated in different scenarios and it was found to be capable of providing detection and identification of parallel and inclined eccentricity. The size of the magnetic field at a specific point in the outer space of the motor was estimated to be 26μT, 30μT, and 43μT, respectively, through analytical modeling in healthy conditions, 10% and 30% eccentricity, and it was confirmed by experimental testing. Since the proposed method does not require installing sensors or search coils within the motor, such a method is more appropriate for practical applications and improving the cost-performance in online condition monitoring. In addition, with some specific modifications, the suggested concept becomes useful for fault detection in other rotating machinery types.