Assessment of single phase SRM converters for low power applications

Abstract

The switched reluctance machine (SRM) is the least expensive machine to produce yet is very reliable. The drive system for an SRM has to be designed so that there is integration between the machine and the converter-controller configuration. This thesis represents a study relating to power electronic converters for single-phase switched reluctance machine drives with emphasis on the cost of implication of the converters. The study of the converters results in the proposal of a new converter concept based on minimising the cost contribution of the dc link capacitor. By reducing the size of the capacitor, smaller and lighter SP-SRM drive is achieved. A detailed analysis and simulation of the proposed converter has been conducted and enabled a design guideline for the proposed converter to be laid out. A model of the SRM with hysteresis controller is developed. Consequently, components have to be chosen carefully to minimise voltage dip, component stress, and energy loss from the freewheeling resistor. To verify the operation of the new converter, tests were conducted on an experimental rig. The proposed converter has the ability to supply double the peak supply of voltage to the machine winding. In addition, the arrangement of the capacitors and diodes in the voltage multiplier means that positive and negative voltage rails can be supplied to the machine, which is very useful in an SP-SRM drive. The high voltage allows the fast magnetisation of the windings and enables the machine to achieve potentially high speed. Through the arrangements of the capacitors and diodes, the converter is able to handle recovered energy form the windings.