Switched reluctance motor(SRM)drives are favored in many industrial applications because of their cost advantage and ruggedness. However, the torque ripple and bus current ripple of SRM restrict its application range  compared with traditional AC and DC motors due to the doubly salient pole structure and the highly non-linear coupling between torque, rotor position and phase current. As a result of the torque ripple on the shaft, unwilling large acoustic noises are generated. The large current ripple at the DC bus input requires large electrolytic capacitors for attenuation. However, electrolytic capacitors are of low reliability, which will reduce the duration of the control system. Because of these disadvantages, the acceptance of SRM by the industry, especially in servo-type applications which require stationary torque at low speed, is quite slow. In order to obtain high quality control, there have been many efforts in developing techniques for torque ripple attenuation. Primarily, two approaches are used to give a smooth torque. One is to improve the magnetic design, the other is to use sophisticated control techniques. Some torque control techniques have been proved to obtain a relatively good performance by simulations and experimental results. This thesis gives an alternative torque ripple minimization technique. Simulations and Experiments are conducted to show the effectiveness of this new control scheme. Under this new control scheme, the current controller are much easier to be designed under high speed application, which could be an advantage of it. First, the SRM operating principle is presented. The torque of SRM is produced by the tendency of its moveable part shifting to a position where the inductance of the exited winding is maximized. The torque ripple origin is discussed in terms of both magnetization and control. The torque ripple is produced during phase commutation interval because the phase current cannot rise from zero to the nominal value instantaneously due to the existence of the phase inductance. Second, a new torque control scheme is proposed. The new torque control of SRM is split into two cascade sub-tasks. At first, a current reference for ripple free torque is determined. Then a current controller is designed to regulate the current in the stator winding to reference value. Simulations are conducted to verify the effective of this torque control scheme in both ideal 'sinusoidal' SRM and a 'Pseudo-Sinusoidal' SRM. Finally, a motor drive control system is built to implement the new control scheme. The motor is tested under different speeds to see the torque ripple produced in different speed ranges. As a conclusion, the new control algorithm for constant torque and damped input bus current ripple is investigated. The advantages of this new torque control method are listed in the paper. Simulation and experimental results show the effectiveness of this new control method. / Master of Science

Doubly-Salient Reluctance Machines (DSRMs) sidestep many of the issues with permanent magnet and induction machines and embody the lowest cost and simplest manufacturing of the motor technologies. Major drawbacks to RMs have been (1) the need for failure-prone electrolytic capacitors, (2) large torque ripple, and (3) acoustic noise. Conventionally, these drawbacks have been addressed independently either through (1) excitation control or (2) machine design, but not as a holistic system or solution. This disseratation presents a design for high-efficiency low-cost RM while producing smooth output torque and avoiding pulsating inverter input current and the associated electrolytic capacitor. We propose a method for shaping the machine reluctance profile to reduce machine torque ripple to a desired level (here, <5%) without compromising on machine efficiency or power density, a Shaped Reluctance Machine (ShRM). Furthermore, a comprehensive approach which combines both phase excitation control and machine design to cooperatively address the excursions of input and output powers from their average values which results in less than 5% ripple for both electrical and mechanical net power — essentially a DC Reluctance Machine (DCRM). Compared to conventional practice in DSRMs, electrical power ripple is reduced by 85 times and torque ripple is reduced by almost 20 times, while overall efficiency, torque density, and power density are maintained. / Ph. D.