Research On Permanent Magnet Machine With Fractional Slot Concentrated Windings

Permanent magnet (PM) machines have lots of advantages such as smaller size, higher efficiency and higher power factor. They can be widely used in various industrial applications. With the emergence of new magnetic materials and the development of manufacturing technology, the unit capacity of PM machine is increasing year by year. However, disadvantages of traditional PM machine with integer-slot distribution windings (ISDW) are emerging gradually in low speed applications. With the increase of slots and poles, the machine design and manufacture become more difficult. In addition, the fact that the winding end of distribution winding is always long leads to the machine has more losses. Thus, fractional-slot concentrated windings (FSCW) are paid more attention and adopted widely in low speed PM machines. This thesis mainly studies winding theory, electromagnetic design, cogging torque and unbalanced magnetic force (UMF) of PM machines with FSCW. It is significant to improve design level and promote application of this kind of machine. The research contents are as follows:1. Theory of FSCW is studied, mainly focusing on the constructive conditions. A method of winding arrangement for FSCW under double layer or single layer is proposed. Winding arrangement for any FSCW can be completed through the proposed method. The winding factors of PM machine with FSCW under double layer or single layer winding arrangements are analyzed through formula method and potential method, respectively.2. The inherent relationship between multi-slot multi-pole machines and their unit machine is revealed. The FSCW-PM machine with 9 slots is chosen as the study object, because the number of derivative machines is larger and their winding factors are higher. The FSCW-PM unit machine with 9 slots is designed and its electromagnetic performance is analyzed. A FSCW-PM machine design software is developed, which can improve the efficiency of machine design.3. The generating mechanism of cogging torque is discussed and analytical expression is derived. The inherent relationship of cogging torque between the designed machine and its derivative machines is studied. The effects of pole and slot combinations, pole arc coefficient, width of slot opening, etc. on cogging torque of the designed 9 slots unit machine are analyzed, respectively.4. The generating mechanism of UMF is discussed and analytical expression is derived. The inherent relationship of UMF between the designed machine and its derivative machines is studied. The effects of pole and slot combinations, pole arc coefficient, width of slot opening, thickness of tooth tip, etc. on UMF of the designed 9 slots unit machine are analyzed, respectively.