Torque Per Amoere Strategies in Switched Reluctance Machines at Low Speeds

• Other Authors: Akar, Furkan (authoraut)
• Format: Others
• Language: English; English
• Published: Florida State University
• Subjects: Electrical engineering; Computer engineering
• Online Access: http://purl.flvc.org/fsu/fd/FSU_migr_etd-4685

The Switched Reluctance Machine (SRM) is one of the oldest members of the electric machine family; it is known for its simple structure, ruggedness, and inexpensive manufacturability. Despite its numerous advantages, at low speeds the SRM suffers from the torque ripple which is not significant at high speeds due to the fact that it is filtered by the moment of inertia of the rotor. Therefore, its torque control at low speeds is crucial. The SRM is a highly nonlinear machine; in the case of multiphase excitation, it becomes more nonlinear due to the mutual coupling effects; ignoring these effects may cause error in anticipating the electromagnetic torque, and increase the torque ripple. In addition, the minimization of the copper losses is another important task; because high copper losses reduce the available phase voltage, decrease the service life of the battery in case it feeds the SRM. In short, the copper losses affect the efficiency of the SRM control system. Finally, it can be claimed that the objectives of an effective and efficient SRM control should be to reduce the torque ripple while considering the nonlinear characteristics of the machine as well as the mutual coupling effects, and to increase the efficiency by minimizing the copper losses. This thesis proposes a new maximum torque per ampere (MTA) strategy, which aims to reduce not only the torque ripple, but also the copper losses, for SRMs at low speeds, while mutual effects between adjacent phases are taken into consideration. The Finite Element Analysis (FEA) is conducted to obtain the electromagnetic torque and flux-linkage characteristics of a 4-phase 8/6 SRM under both single and multiphase excitation. After this step, the optimum phase current profiles are determined by the proposed method based on the Particle Swarm Optimization (PSO). This new methodology is then validated by comparing it with the conventional control method and the `balanced commutator' method, which is an efficient MTA strategy. These comparisons are realized via the static and dynamic SRM models which utilize the data retrieved from the FEA. Real hardware results are taken from another 4-phase 8/6 SRM under both the singlephase and multiphase excitations so as to derive its torque-angle characteristic. Subsequently, demanded current values for different torque levels are computed according to the conventional, `balanced commutator', and PSO methods. Finally, the PSO technique is judged against the other two methods at some selected rotor positions in terms of the torque ripple, copper losses and torque per ampere ratios. === A Thesis submitted to the Electrical and Computer Engineering Department in partial fulfillment of the requirements for the degree of Master of Science. === Summer Semester, 2012. === June 25, 2012. === Intelligent Algorithms, Maximum Torque per Ampere, Particle Swarm Optimization, Switched Reluctance Machine, Torque Ripple === Includes bibliographical references. === Chris S. Edrington, Professor Directing Thesis; Petru Andrei, Committee Member; Mark H. Weatherspoon, Committee Member.