During recent years, there has been increased interest in the incorporation of fractional-slot concentrated stator windings (FSCW) into permanent magnet machines for high power density applications. This thesis focuses on the opportunities for extending this FSCW technology to interior permanent magnet (1PM) machines, highlighting both the merits and limitations of this combination.;This thesis proposes development of an electromagnetic lumped-parameter magnetic circuit model (MCM) specifically tailored for the FSCW-IPM machine. MCM is typically much faster to solve since it contains a small fraction of the nodes used in standard electromagnetic FE calculations with reasonable accuracy. The calculation speed advantage makes the MCM highly attractive for use in 1PM machine design optimization programs to explore multi-dimensional design spaces.;Presence of high degree of electromagnetic nonlinearities that are associated with high-performance IPM machine designs makes the development of an MCM with sufficient accuracy highly challenging. The resulting MCM for FSCW-IPM machines is capable of accurately estimating the machine's flux linkages, torque, voltages, and iron core losses for a wide range of current excitation operating points.;This research program includes an investigation saliency trends in FSCW-1PM machine configurations and their dependencies on key machine design parameters such as the slots-per-phase-per-pole (SPP) value. The trends in magnetic saliency of FSCW1PM machines clarify the reasons for the typical dominance of magnet torque in FSCW1PM machine designs.;A detailed design of a 55 kW (pk) FSCW-IPM machine for an automotive traction application together with experimental verification on the resulting prototype machine confirms the MCM's accuracy. The generality and scalability of the MCM are also demonstrated by comparing its predictions with FE for several FSCW-IPM machines with a variety of power ratings, winding configurations, numbers of phases, as well as exterior rotor configurations.;Finally, this research also addresses the structural modeling of IPM machine rotors and the special challenges associated with these rotor configurations. Structural design optimization methods are developed to minimize the sum of the widths of the rotor magnet cavity bridges and center post in order to reduce the amount of magnet shorting flux, thereby increasing the machine's power density.
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