Dual Voltage Supply Converter for High-Speed Doubly Salient Reluctance Motors

Small variable speed drives intended for mass-market applications like hand-held power tools and household appliances have to be inexpensive and efficient. Doubly salient reluctance motors are known to be cheap and robust, but their use in such mass market applications has been hindered by the cost and limitations of their associated power converters. A new converter concept is proposed in this paper. The new converter has the ability to apply higher voltages across the machine windings than could be obtained with standard circuits to achieve high-speed operation. The demagnetization of the machine coils is load independent ensuring fast current decay and consequently a stable high-speed operation at higher loads. The fast rate of current decay allows a longer duration of positive torque pulses resulting in less pulsating torque. A detailed analysis of the proposed converter is presented and design guidelines are laid out. A 1-kW prototype converter is designed and constructed to experimentally validate the operation of the new circuit.