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In recent years,with the improvement of the permanent magnet materials’magnetic properties, and the decreasing of the price of materials, coupled with the many advantages of permanent magnet generators, more and more field are using permanent magnet generator. Permanent magnet generator has the advantages of small size, low loss, high efficiency, when energy conservation and environmental protection are taken seriously increasingly in today, so it is very necessary to its research. But the instability of the output voltage limits the application of the permanent magnetism generators, in order to solve the unsteady problem of permanent magnet generator’s output voltage, to most people, they research it form the motor body and the external power electronics circuits two aspects.This paper analyzed the structure and character of earth rare permanent magnet synchronous generator in detail, selected generator’s stator and rotor structure according to actual conditions. The rotor adopted radial excitation structure that generator internal structure arranges more closely. Permanent magnetic material adopted NdFeB, which has the advantages of high magnetic energy product, high remanence induction, and straight demagnetization curve and so on.This study started from the internal structure and working principle of permanent magnet generator, analyzed internal factors which influence the generator’s output voltage, which is the armature reaction. To reduce the influence on generator’s output voltage, firstly optimized flux density operating point of stator tooth and generator structure, then optimized the size of air gap.Finally, to improve the performance of permanent magnet generator and expand the scope of application, and also provide a reference for the optimal design in future, appropriate parameters were obtained, the output voltage of the generator was controlled.This study constructed geometric model and the two-dimensional model on the basis of the finite element analysis software Ansoft12.1, and calculated the transient field based on the two-dimensional model. Simulation results coincide with practice operation results, so this method can be used for generator’s optimization design. Through the result of transient field calculating, we can observe distribution of magnetic line of force and B,besides the influence on generator’s output voltage, and confirm the structural parameters and materials of generator, that Stator material is D23, the best operating point stator tooth is 1.8T, the width of stator yoke is 5mm; the pole arc coefficient of rotor magnet is 0.6, the width of air gap is 1.5mm; permanent magnets select NdFeB N48 (Br=1.38THc=870kA/m),which width is 2.5mm.
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