Three-phase Permanent Magnet Switching Flux Motor

Novel PM doubly-salient motors developed from switched reluctance motor have been extensively studied since the switched reluctance motor was invented. These doubly-salient motors have coils and magnets in the stator, but not in the rotor. Therefore, the motor structure is very simple, and manufacture cost is low. Along with the development of the modern power electronics techniques, CAD and microcomputer control techniques, the problems on the topology, control and drive design of the doubly-salient motors have been solved effectively.The PM flux-switching machines studied in this thesis, which have a magnet imbedded in each stator tooth, combine the merits of both switched reluctance motor and PM motor, such as simple structure, robustness, fault tolerance, high efficiency, etc. In addition, the disadvantages of the switched reluctance motors, such as complicated control, acoustic noise and vibration, are effectively overcome. In the PM flux-switching machines, the PM-excited flux always exists and has a constant direction in the magnet. However, the flux path changes with the rotor position, resulting in variation of both amount and direction of flux-linkage in the stator coil, and thus inducing back-EMF. The machines can be driven as a BLDC or BLAC machine.The phase back EMF, cogging torque, radial force of the PM flux-switching machines are computed with finite element analysis software in the optimal design. The FEA results of the machines with different geometric variables such as stator pole arc and rotor pole arc are comparatively studied. Some topology geometric variables are optimized in order to enhance the machine performane.There are two different structure machines studied in this thesis, viz, structure 6/4 and structure 6/5. Cogging torque exists in both machines, and unbalanced radial force exists in the 6/5 motor. These are harmful to the machine's performance, so rotor skewing is used in order to reduce or eliminate the cogging torque and radial force.Finally, the machines are prototyped, with a same stator and four different rotors, the static and stable operation performances of the prototypes are tested. The experimental results agree with the above-mentioned FEA results. It is seen both in experimental results and FEA results that the 6/5 machine has a much higher back EMF coefficient and fewer EMF harmonics than the 6/4 machine, indicating a superior torque capability.