Utilization of Multiple Planar Search Coils for Diagnosing Imbalance Irreversible Demagnetization Faults in PMSMs along the z-Axis

Permanent magnet synchronous motors are widely employed in various fields due to their excellent efficiency and output characteristics. However, magnets are susceptible to irreversible demagnetization faults (IDF), where their magnetic properties degrade due to stresses such as external magnetic fields and high temperature condition. IDF can deteriorate motor performance and even lead to catastrophic failures like control failures. Therefore, there is a need to study diagnostic techniques for IDF. Various diagnostic techniques have been proposed; However, due to the uneven distribution of stresses, such as heat and magnetic flux, on the motor magnets, IDF exhibit non-uniformity along the z-axis direction. Most of fault detection method cannot provide diagnostics for individual magnet segments. In this paper, a fault diagnosis technique using planar search coils attached to the surface of the motor's stator is introduced. The planar search coils can be fabricated in various shapes, allowing for the arrangement of multiple coils along the z-axis of the motor to acquire signals based on the flux linkage on each coil. This technique is validated through finite element method and experiments. As a result, it is confirmed that the proposed technique allows for fault diagnosis in both the non-excited and excited states using the acquired signals.