Inverter Drive for Doubly Salient Reluctance Motor: Its Fundamental Behaviour, Linear Analysis and Cost Implications

A variable-speed drive using a doubly salient variable reluctance motor, because of its ability to operate efficiently from unidirectional winding currents, enables the number of main switching devices in the inverter to be halved, yielding a very economical brushless drive. The drive is analysed using a linear model for the motor, yielding phase-current waveforms which enable an economical design for the thyristor inverter and provide guidance for a motor design which will optimise the performance/cost ratio of the drive as a whole. A control strategy for firing and turning off the inverter thyristors at appropriate rotor angles for a traction application also emerges from the analysis. Experimental waveforms exhibit shapes similar to those predicted, and the results of this analysis have been of great value in designing such a drive for a battery vehicle.