Comparison of interior and surface PM machines equipped with fractional-slot concentrated windings for hybrid traction applications

Electric drive systems, which include electric machines and power electronics, are a key enabling technology for advanced vehicle propulsion systems that reduce the petroleum dependence of the ground transportation sector. To have significant effect, electric drive technologies must be economical in terms of cost, weight, and size while meeting performance and reliability expectations. This paper will provide details of the design, analysis and testing of two permanent magnet (PM) machines that were developed to meet the FreedomCar 2020 specifications. The first machine is an Interior PM (IPM) machine and the second machine is a surface PM (SPM) machine. Both machines are equipped with fractional-slot concentrated windings (FSCW). The goal of the paper is to provide a quantitative assessment of how achievable this set of specifications is as well as a comparison with the state of the art. The paper will also quantitatively highlight the tradeoffs between IPM and SPM FSCW machines especially in the context of traction applications.