A Microprocessor Control Scheme For Switched Reluctance Motor Drives

Abstract

Electrical Engineering (ABSTRACT)A microprocessor control scheme for variable speed switched reluctance motor(SRM) drives . is discussed. A particular implementation derived from first principles of the SRM is presented. The Intel 8088 microprocessor is used for the design implementation. It is shown that given the control requirements of the SRM like firing different phases according to rotor position and phase currents, a microprocessor controller is a good choice. The controller is economical since it uses standard TTL chips. The slow response at low speeds is also discussed. Experimental results performed on a static inductive load using a simulated position feedback are presented, showing how the current control available at lower speeds is lost at higher speeds, due to limited de bus voltage. A listing of the controller software with adequate comments and the circuit diagrams are appended. AcknowledgementsI would like to acknowledge the constant guidance, support and encouragement of Dr. Ramu throughout this project and my coursework. I have learned a lot from my association with him.I thank Dr. Nunnally for loaning equipment and giving useful tips. It has been a pleasure knowing him and working with him. I thank Dr. Rahman for agreeing to be on the committee.If ever there was a collection of nice people in one place, it is the EE Shop at Virginia Tech.This project would not have seen the light of day had it not been for the constant support of the EE Shop personnel. Whether it was a hardware problem or an urgent need for parts and equipment they always came through. I am particularly grateful to for his support and advice on the use of Laboratory equipment. I learned a lot about hardware and electronics from talking to who was always willing to discuss a problem. The 1960's saw the use of high-power semiconductor switches. These were fast and reliable. Angular position could also be measured using position encoders now.These advances rekindled an interest in the SRM. An improved understanding of the Introduction magnetics led to the machines being driven to saturation to get better efficiencies [3].lnspite of the progress, the main drawback of the machine is a pulsating torque which precludes it from high-performance applications. Efforts are on to design motors, converters and controllers to give a smooth torque output. Literature SurveyThe literature available on the SRM may be broadly classified into three segments: circuit without using position sensors. The machine efficiencies, using such a control were found to be extremely low and only suitable for low-end aplications. ObjectiveThe SRMs are inherently variable-speed drives, since they need a converter for its operation. The control strategy may be implemented using analog or digital components. A digital control scheme enables the use of a microprocessor. The objective of this project is to design, build and test a microprocessor controller on a prototype drive system. This would allow data to be collected for various parameter and design cha...