Losses in High Speed Fractional Slot Concentrated Winding Surface Permanent Magnet Machines

Increasing demands for smaller and lighter ac machines in many transportation and industrial applications have intensified efforts to design high-speed ac machines that combine high power density and high efficiency. The resulting increases in excitation frequencies aggravate several loss mechanisms in the machine.;The objective of this thesis is to develop analytical models to predict special iron and stator winding loss components that occur during high-speed operation of fractional-slot concentrated-winding (FSCW) surface permanent magnet (SPM) machines. Closed-form analytical techniques are used to predict the flux distribution in the slot, including conformal mapping. The flux density solution impinging on each strand and bundle is used to estimate the individual proximity loss components.;An integrated analysis tool has been developed for predicting the total proximity losses in the slots of a FSCW-SPM machine. The model accounts for both strand-level and bundle-level losses caused by either armature reaction caused by the high-frequency stator currents or the rotating rotor flux contributed by the magnets. Results from this model have demonstrated the importance of transposition of the stator windings in FSCW-SPM machines in order to minimize proximity losses due to circulating currents.;The thesis also presents a model for estimating the iron losses in the stator teeth tips of FSCW-SPM machines based on analytical solutions for the magnetic flux densities using conformal mapping techniques. Tooth tip design details are important because a significant fraction of the total stator iron losses is concentrated in these structures during high-speed operation. The model has demonstrated its ability to deliver teeth-tip loss estimates that match finite element predictions within 15% for a prototype high-performance FSCW-SPM machine.;A prototype 55 kW (peak) FSCW-SPM machine with 12 stator slots and 10 poles has been built using a segmented stator structure and three-phase double-layer concentrated windings. Fabrication details are presented along with a combination of predicted and measured performance characteristics that highlight both the advantages and limitations of FSCW-SPM machines for demanding traction applications. The results of this testing have provide important confirmation of the new analytical proximity loss model with the aid of three identical stator cores with different stator windings.