Fault Investigation of X-by-wire Permanent Magnet Synchronous Machine

Permanent magnet synchronous machines (PMSM) are used in x-by-wire systems, because of the high efficiency and its good dynamic properties. To investigate the performance of the machine at fault situations, a 3-phase, 16-pole prototype (rated state torque 1.7 Nm, overload torque 20 Nm for impulse torque actuation) with tooth coils was built with the possibility for measuring different kinds of winding short circuit failures. Field calculation of the PMSM was done analytically and numerically. A dynamic model of the drive system, which consists of the motor, the PWM inverter, a PI cascade speed-current controller and a simplified mechanical load, was developed to simulate the faulty operation of the x-by-wire system. The numerical calculation shows, that winding short circuit fault of the PMSM results in motor speed, torque and current ripple with twice the stator frequency. At rated load steady state, the electromagnetic torque ripple for the fault case is 111% of the rated torque, if three adjacent tooth coils of one phase are short circuited. This is about 1.6 times bigger than in the fault case, where one tooth coil is hot-wired. Short circuit fault results in big currents flowing in the stator winding, which harm the motor thermally