Analysis Of Electromagnetic Field In A Switched Reluctance Machine From An Energy Conversion Perspective

With the recent advancement in power electronics and digital signal processors, switched reluctance machine (SRM) attracts more attention in high speed and harsh environment applications due to its rugged and robust structure. Despite considerable progress in the development of power electronics based control of the SRM, relatively small changes in the magnetic design has been observed. A physically insightful analysis of the electromechanical energy conversion process, origins and spatial distribution of electromagnetic field quantities at a microscopic level can shed light on the process of SRM design, which in turn could create new opportunities for substantial improvement of SRM performance such as energy conversion efficiency, torque production, iron loss reduction and acoustic noise mitigation. This thesis introduces various electromagnetic force calculation methods and validates each method with a linear motion actuator model. Then the process of energy conversion in SRM is explored by both electromagnetic theory and simulation, the origin and spatial distribution of flux densities and force densities are studied via finite element analysis. A novel surface Maxwell Stress Tensor (MST) method is proposed to analyze the stress over critical sections of the machine geometry. On the field analysis basis, bipolar excitation and flux barrier placement techniques are introduced as an application of magnetic field alternation technique. Simulations are conducted to prove how respective prescribed goal is achieved.

A comprehensive insight into the energy conversion and field quantities distribution has been the focus of this thesis. This has been verified by finite element analysis. Approaching the electromechanical energy conversion process at a microscopic level, this paper paves the way for further investigation into performance optimization of SRM by both electrical and mechanical design.