Abstract
Switched reluctance motors have been studied in twenty years but the applications have been limited to special cases. One of the main reasons of these limited applications is the complicated machine model and unclear operating characteristics of switched reluctance motors. Conventional synchronous motor models are not applicable because the current waveforms of switched reluctance motors include dc component and considerable amount of harmonics. A simple analytical model and normalized characteristics of switched reluctance motors are needed to express voltage, current and torque relationships.
In this paper, the inductance variations of a switched reluctance motor are represented only by a fundamental component and a constant. Terminal voltage is also approximated as sinusoidal. With these approximations, the relationships of normalized voltages, currents and output powers are derived. It was found that the power to voltage ratio can be maximized at a particular voltage phase angle θv. It was also shown that there is another voltage phase angle θi, which maximizes power to current ratio. The most efficient operation of switched reluctance motors can be realized with the voltage phase angle between θi and θv. These analytical results were confirmed with experimental results of a test machine rated 2.2kW at a speed of 6, 000rpm.
