SPM Motor with Star-Delta Winding: Fault Analysis and Experimental Validation

A surface-mounted permanent magnet (SPM) motor is designed to address a winding with a combination of star- and delta-connected coils. At first, it is shown that the star-delta winding connection commonly presented in literature is strongly dependent on where the fault occurs, that is, it is not proper to tolerate the open-fault in the wye part. Then, a different winding connection is investigated, showing that this exhibits a much higher tolerance to open-circuit faults. In particular, the solution is characterised by the wye-connected coils completely in parallel with the delta-connected coils and it is referred to as “Star-parallel-Delta” connection. The motor torque behaviour is simulated and experimentally tested in healthy conditions as well as with some open-circuited coils. The currents in the coils are analytically computed by means of a lumped parameter model and used in the finite element analysis to predict the torque behaviour. Experimental results are compared to the analytical predictions, finding a suitable match. Different open-circuit faults are analysed and tested, with the aim of investigating the behaviour of the motor in post-fault conditions.