Analytical Modeling of Interturn Short Circuit for Multiphase Fault-Tolerant PM Machines with Fractional Slot Concentrated Windings

Interturn short-circuit faults that occur inside stator coils are difficult to cope with compared with terminal short-circuit faults. A general analytical model for interturn short-circuit faults is developed that employs a novel T-type equivalent circuit. When this model is used to investigate the impact of interturn short-circuit faults in permanent-magnet (PM) machines with fractional slot concentrated windings (FSCW), the model delivers fault response predictions that agree very well with results from the finite element analysis. The model is used to show that the 24-slot/14-pole FSCW PM machine is vulnerable to very high interturn fault currents, even when the remaining turns are shorted, offsetting its advantage of low magnetic coupling between phases. FSCW-PM machines that employ aligned coils in phase windings can effectively suppress their interturn fault currents. Experimental verifications are provided for the 24-slot/22-pole FSCW PM prototype machine (with two aligned coils per phase) under the single-turn short-circuit fault.