Design and Development of Brushless Variable Speed Motor Drive for Low Cost and High Efficiency

Low cost brushless motor drive systems are actively sought for high efficiency home appliances and power tools. Minimizing the number of switching devices has been in power converters is the main method to reduce drive costs. Single-switch-per-phase converters have been cost-effective due to compactness of the converter package resulting in a possible reduction in their cost. However, some of single-switch-per-phase converters have the drawbacks that include higher losses and low system efficiency. In order to overcome these shortcomings, the choice narrows down to the split AC converter through the quantitative analysis in terms of device ratings, cost, switching losses, conduction losses, and converter efficiency. Simulations to verify the characteristics of the converter circuit and control feasibility are presented. The motor drive is realized with a novel two-phase flux-reversal-free-stator switched reluctance motor and a split AC converter. The efficiency with various loads is numerically estimated and experimentally compared in this paper. The acoustic noise with no load and full load is also compared. The focus of this paper is to compare the considered split AC converter to the asymmetric converter through experiments and demonstrate that the split AC converter is the most advantageous with respect to cost, efficiency, and acoustic noise.