| With advantages of high power density, low cogging torque, strong fault-tolerance ability and et al, fractional slot concentrated winding permanent magnet synchronous machines (FSCWPMSM) have wide application prospects in wind power generation, ship propulsion and electric vehicles. Recently, the research on FSCWPMSM is mainly on slot/pole combination, electromagnetic vibration and additional losses due to magnetic motive force (MMF) harmonics. The distinctiveness of its winding and magnetic circuit makes its analysis of parameter and performance, as well as electromagnetic design is very different from traditional integer slot per pole per phase machines. In this dissertation, FSCWPMSM is studied systematically, focusing on related problems in design and analysis.Based on star of slots, an effective method for calculation of winding factor in any harmonic order, with any slot/pole combination is established, suitable for both single layer and double layer winding. A large variety of slot/pole combination are analyzed, and the regularity of winding factor with slot/pole combination is summarized. Based on obtained winding factor and winding theory, the harmonics of three phase synthesis MMF is analyzed. Then, comparison between different slot/pole combination types is made, using winding factor, vibration mode, cogging torque and losses as evaluation index.An Analytical method for calculation of three phase self-inductance and mutual inductance is proposed based on winding function theory. The slot leakage inductance formula of concentrated winding with different slot/pole combination is deduced. The analytical method are compared with finite element method, the results are in good agreements for surface mounted FSCWPMSM. The influence of slot dimensions, as well as the current angle on phase inductance is studied. Three methods for computation of d-axis and q-axis inductance, namely, the vector control method, frozen permeability method and differential flux linkage method are compared.In-depth study on field weakening characteristics of permanent magnet machines is carried out. The influence of characteristic current, saliency ratio and permanent magnet flux linkage in per unit value on field weakening characteristics are investigated. The mechanism of field weakening improvement in segmented interior permanent magnet synchronous machines is revealed by frozen permeability technique. The field weakening performance of four design schemes including FSCWPMSM and integral slot per pole per phase permanent magnet machines are analyzed and compared.The magnetic loading and electric loading have great impacts on radial force density and losses, including both iron losses and eddy current losses in magnets. Both the magnetic loading and electric loading could change with the current amplitude and current angle. The radial force density of surface mounted FSCWPMSM under different load condition is analyzed by analytical method. For interior type FSCWPMSM, finite element method is used. The stator iron loss, especially in stator tooth tip, and eddy currents losses in both surface mounted and interior type FSCWPMSM are analyzed considering the variation of magnetic loading and electric loading. |
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