Supply current polar chart analysis of SRM drives under normal and faulty operating conditions

A polar chart of the power converter supply current, comprising phase currents and rotor mechanical position information, is presented, in order to characterize the dynamic operation of a SRM drive. Power converter supply current can be used as additional information of extreme importance when a sensor error or failure occurs. Its analysis is then important and permits to develop appropriate fault tolerant control strategies to solve failures or errors on phase current measurements. Time-domain waveforms of the phase currents and power converter supply current are presented and discussed. Two different speed operating conditions examples are presented, in order to understand the differences on SRM dynamic behavior in the all speed range. For both situations, the normal and the faulty operation due to the absence of one motor phase are analyzed. The adopted SRM control strategy, based on the electromagnetic torque regulation, is clearly explained for the all SRM speed range.