A novel power inverter for switched reluctance motor drives

Although apparently simpler, the SRM drives are nowadays more expen- sive than their conventional AC drive counterparts. This is to a great extent caused by the lack of a standardised power electronic converter for SRM drives, which would be available on the market as a single module. A number of attempts were therefore made in recent times to develop novel power electronic converter structures for SRM drives, based on the utilisation of a three-phase voltage source inverter (VSI), which is readily available as a single module. This paper follows this line of thought and presents a novel power electronic converter topology for SRM drives, which is entirely based on utilisation of standard inverter legs. One of its most important feature is that both mag- netising and demagnetising voltage may reach the DC-bus voltage level while being contemporarily applied during the conduction overlap in the SRM adjacent phases. At the same time, the voltage stress across the power switches equals the DC-bus voltage. The topology is functional in all operating regimes of the drive. Principle of operation is explained in detail for a three-phase SRM drive and experimental results, obtained with a 6/4 switched reluctance motor, are included. Four inverter legs are required in this case. Some considerations, justifying the proposed converter topology from the point of view of the cost, are included.