Design and Experimental Verification of a Short-Circuit Proof Six-Phase Permanent Magnet Machine for Safety Critical Applications

By making use of leakage flux components, a multiphase permanent magnet (PM) machine constructed with fractional-slot concentrated windings can confine winding short-circuit current to rated current to avoid further damage when the stator winding gets short-circuited. However, those high-winding-inductance machines suffer from high PM demagnetization risks. Design principles to avoid PM demagnetization are discussed in this paper to deal with this issue. In addition, mathematical analyses of short-circuit current and torque pulsations are developed, which reveal the physical nature and offer an effective way to investigate the machine performances. Short-circuit fault remediation methods utilizing two-phase symmetry of asymmetric six-phase machine is proposed. Furthermore, a 24 kW prototype machine was fabricated and experimental verification has been conducted.