Fault-Tolerant Redesign of a Quad-Winding PMSM to Prevent Irreversible Partial Demagnetization

This paper proposes a fault-tolerant optimal design method for quad-winding permanent magnet synchronous motors (PMSMs) considering irreversible demagnetization under fault conditions. In quad-winding motors, when one or more winding sets become unavailable, the remaining windings must carry higher current to maintain the required torque. This increases the external magnetomotive force acting on the permanent magnets and may cause irreversible demagnetization, particularly in spoke-type magnet structures. To address this issue, the demagnetization characteristics of the quad-winding motor were analyzed under healthy and faulty operating conditions. Based on this analysis, an optimization process using a Radial Basis Function–Multi-Layer Perceptron (RBF–MLP) surrogate model and a combination of grid-based search and local optimization was applied to obtain an optimal motor design. The optimization results show that the irreversible demagnetization ratio was reduced from 5.9% to 0.5% while maintaining a similar magnet volume. The proposed design approach effectively suppresses irreversible demagnetization in quad-winding PMSMs.