Electromagnetic Force on Individual PM Modules for Immobilization in Fractional-Slot Surface-Mounted PM Wind Generator

Existing studies of noise and vibration predominantly explored the electromagnetic force of the entire machine. However, in surface-mounted permanent magnet wind generators, the electromagnetic force can be utilized to immobilize pole modules. Therefore, this article focuses on the global concentrated force acting on an individual pole with a baseplate arrangement. The force contributed by magnets, currents, and their interaction, are compared in a multi-three-phase fractional-slot generator. Notably, the analysis evaluates the forces not only on the commonly studied surface facing the stator air-gap but also on the rest of surfaces of the module. Under no-load condition, it is found the module can withstand an excessively large fluctuating tangential force, leading to possible reciprocation. When loaded, the interaction of two fields significantly amplifies fluctuations in radial and tangential forces despite that the multi-three-phase currents reduce the armature field harmonics. The radial force, especially under heavy electric loading, can cause the pole to detach from the rotor. The findings highlight the crucial concerns and challenges associated with reliable immobilization. At last, a dedicated experimental setup is designed to measure the magnetic force between a pole module and modular rotor iron.