Design of an Integrated Starter-Alternator for a Series Hybrid Electric Vehicle: A Case Study in Axial Flux Permanent Magnet Machine Design

Authors

Jessica L. Colton, University of Nebraska at LincolnFollow

Date of this Version

Winter 2010

Document Type

Article

Comments

A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Interdepartmental Area of Engineering (Electrical Engineering), Under the Supervision of Professors Jerry Hudgins and Dean Patterson. Lincoln, Nebraska: December, 2010
Copyright 2010 Jessica L. Colton

Abstract

This thesis details the design of an electric machine to perform as both a starter and alternator in a series hybrid electric vehicle. The focus of the work is on practical design aspects specific to single-sided axial flux permanent magnet machines with non-overlapped windings. First, a characterization of the rotor losses in these machine types is presented through experimental validation of finite element analysis estimates. The approaches taken to model the axial flux geometry, especially in two-dimensions, are detailed, and the difficult issue of validating the finite element analysis estimates with experimental data is addressed with a prototype 24-slot, 20-pole single-sided machine fitted with single-layer non-overlapped windings. Next, the comparative advantages and disadvantages of the single-sided axial flux geometry and the most common form of radial flux structure, with an inside rotor, are explored within the context of surface mount permanent magnet machines. New material is offered which highlights the benefits of the single-sided axial flux geometry and the constraints and assumptions made when making the comparisons are discussed in detail, including a study of the biases these can introduce. The basis of comparison is founded on constant electromagnetic airgap shear stress, being the product of electric and magnetic loading, and indeed the constancy of both those factors. The metrics used for comparison are the mass of the active materials and the volume essential to house said materials. A range of lesser issues that are relevant when choosing a machine structure are presented and discussed. Finally, the performance criteria for the integrated starter-alternator are quantified based on characterization of the internal combustion engine and the energy storage system of the vehicle and a full account of the design process is detailed, including justification of all design choices.