An electromagnetic actuator driven by a power electronics converter is a mature technology in industry. However, it faces reliability issues due to the failure of power electronics devices in the drive. Post-failure system often retains a substantial amount of kinetic energy, necessitating the implementation of online diagnosis and fault-tolerant control, especially in high-speed rotating machinery and critical non-interruptible applications. Typically, the recovery of regular motor drives after a failure involves two methods: hardware backup and model based current reallocation. However, for actuators with ferromagnetic targets, there is inherent fault-tolerant potential that offers greater flexibility, stronger robustness. These ferromagnetic targets are driven by Maxwell force, independent of the current direction. The physical nature of Maxwell force in macro and microscopes have been explored in this article. Notably, the characteristics of power electronics legs can accommodate different current directions. Leveraging this consistent symmetry between Maxwell force and legs, we use switched reluctance machine (SRM), which generates tangential forces, and active magnetic bearing (AMB), which generates radial suspension forces, as examples to analyze the strategy. Moreover, its universality helps to be applied to various power electronics topologies and aligns well with existing control framework. The proposed method fully exploits the fault tolerance potential, significantly enhancing system reliability.
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