Design and steady-state analysis of the switched reluctance motor drive

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Virginia Polytechnic Institute and State University

In the last two decades there has been a revival of interest in variable reluctance drives mainly due to the advent of high power semiconductor devices and improvements in the understanding of the principles of electromagnetic energy conversion. In particular, the switched reluctance motor (SRM) has received attention mainly due to its simple construction and robustness when compared to other variable-speed drives. Considerable research has been done on topics ranging from the design to the control of the motor. Due to the high nonlinearity of the machine, even the prediction of the steady-state performance of the drive has been difficult. In the attempt to overcome the nonlinearity problem, researchers have resorted to computer solutions. The Finite Element Analysis (FEA) method has been used to predict the steady state performance of the motor. While this has improved the accuracy of performance prediction, it is very time intensive. This is unacceptable in an industrial situation where the PC is the main design tool. The need for analytical methods therefore exists. An analytical method for the steady-state performance prediction of the SRM drive based on an improved method for estimating the maximum and minimum inductances is described. This method is extended to include determination of the motor inductances at any rotor position and subsequently, the prediction of the steady-state average torque. The work also proposes an analytical method for determining the core losses of the SRM. Considerable effort is also dedicated to the design and analysis of new and old SRM converter topologies with particular attention to the criteria governing the choice of converter topology, the prediction of key waveforms, the criteria for selecting power semiconductor devices and the determination of device ratings. A novel method for the direct steady-state analysis of the SRM drive without going through the transient solution is proposed. The effect of motor geometry on converter ratings is also investigated for the common SRM pole combinations. Novel methods for the measurement and instrumentation of SRM are also described. Theoretical predictions are verified by experimental results using a 6/4 pole prototype switched reluctance motor.