Stator inter-turn fault detection in SPM machines using PWM ripple current measurement

In this paper a novel method of inter-turn fault detection based on measurement of high frequency pulse width modulation (PWM) ripple current is proposed. The method uses the ripple current generated by the inverter itself as a means to detect inter-turn fault. High frequency impedance behaviours of healthy and faulted windings are analysed and modelled, and ripple current signature due to inter-turn faults is quantified. A simple analogue circuit is designed to extract the PWM ripple current via an RMS band-pass filter and the filtered RMS current is used for fault detection. In addition, the method also identifies the faulted phase. The method is tested in simulation on a five phase alternate slot wound SPM machine.