Segmented rotor switched reluctance motors
This thesis introduces and researches the concept of a new form of switched reluctance motor, in which the rotor is made from a series of discrete segments. Single phase machines are initially examined and design rules established. Predictions of air-gap force density are compared with toothed rotor equivalents and it is shown that much greater force densities are theoretically possible with the segmental design. The thesis then proceeds to apply the concepts developed to two different three phase configurations, which show particular advantages. Two demonstrator machines are designed and built, and their method of construction described. Measured static test results are initially presented for each machine and compared with a conventional switched reluctance motor of the same dimensions, revealing both the advantages and disadvantages of the two segmental rotor configurations. Both demonstrator machines are then run as SRM drives, with the current to each phase supplied from an asymmetric half bridge converter. The current and voltage waveforms are monitored, along with measurements of mean torque output. Waveforms are compared with those predicted by simulations and conclusions are drawn regarding the performance of the drive systems. The results of this work clearly demonstrate that segmental rotor SRMs have much greater torque capability than conventional toothed geometries. Of the two demonstrator machines constructed, one has a very high torque per unit loading, but has relatively long end-windings; the other has slightly reduced torque per unit loading but overcomes the problem of long end-windings. Both machines appear to outperform other forms of reluctance motor.