Abstract
This paper focuses on two major issues which need careful consideration when designing an excitation for variable-reluctance motor (VRM( drives. The drive is comprised of a VRM, an inverter and an excitation and control strategy. The controller acts to enforce the excitation. The specific issues addressed here include the modeling of the drive and selecting a topology Toe the drive. These issues were found to be important during the design of an optimal-efficiency excitation for a high-power (60 kW( VRM drive. The drive used for the running example was designed for electric vehicle propulsion using a bifilar wound VRM. The importance of drive modeling is examined through an example. The example uses two magnetic models for the same VRM to generate current waveforms for drive operation at a specific speed. The attributes of the current waveforms are then compared and their influence on excitation design is discussed. The comparison shows that meaningful excitation design requires accurate models of drive operation. The implications of the magnetic model on the design of the VRM are discussed. With regard to inverter topology, a detailed efficiency comparison between a bifilar and a monofilar high-power VRM drive is presented. Each drive is comprised of a motor with identical geometries and the same number of turns per pole, a switching inverter, an excitation strategy and a control algorithm. After examining drive efficiency at several operating points over the intended duty, the paper concludes that the monofilar drive offers increased efficiency over the bifilar drive.

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