Comparative Study on Multiple Three-Phase Permanent Magnet Motors in Fault Tolerant Electric Power Steering Application

Electric power steering (EPS) is a safety-critical compoment in modern vehicles. Along with the rise of connected and autonomous vehicles, an EPS system needs to achieve fail-operational in the event of a fault. Thus, it mandates redundant architecture to increase reliability and performance in steering function. By providing steering assistance, a multi three-phase electric motor is a fault-tolerant solution for a functional safety architecture. This paper presents a comparative study between dual and triple three-phase interior permanent magnet (IPM) motors with single layer winding. The corresponding electromagnetic performance is predicted considering the influence of rotor pole numbers. The detailed comparison is made between dual three-phase 12 stator-slot/10 rotor-pole (12s10p) and triple three-phase 18 stator-slot/10 rotor-pole (18s10p) IPMs in both healthy and fault modes. Primary experiemental results are presented in the dual three-phase IPM motor.