Research Of Magnet Arrayed Modulation Line-Start PMSM

Permanent magnet synchronous machines (PMSM) with the structure of surface-mounted permanent magnet have the characteristics of small in size, good performance, high efficiency and simple process. However, it can only be adopted in the occasion of frequency converter supplied due to its deficiency of line-start. In the traditional rotor with structure of surface-mounted, there are great deals of harmonic component in air gap field, additionally with the high non-sinusoidal voltage and current waveform generated by frequency converter, which results with the increase of harmonic added loss and decrease of efficiency and finally restrict the PMSM's advantage of energy conservation. Furthermore, the application of surface-mounted PMSM is limited because the shortcoming of line-start due to its lack of space to install starting windings.An approach by placing distributed magnet on the surface of rotor and starting windings between magnets, which is named magnet arrayed modulation method, is proposed in this paper. By this novel designing the sinusoidal degree of waveform is improved in permanent magnet synchronous motor and also with the ability of line-start be provided by equiping the starting windings in the gap between magnetsThe theory of magnet modulation with structure of arrayed rotors is given at first. And general formula was given by theoretical calculation and analysis, Then the analysis of flux density waveform in the PMSM with distributed magnet rotor in arrayed modulation was carried out with the finite element method based on a special example of five magnets setting in one pole. Sinusoidal degree comparision between novel magnet arrayed modulation structure and traditional monoblock structrue was obtained by harmonic analysis and introducing of sinusoidal distortion. Meanwhile, the simulation of motor line-start process, which with copper and aluminum windings mounted between distributed arrayed magnets separately, was conducted with ANSOFT. Finally, prototype of motor with traditional monoblocked rotor and magnet arrayed modulation rotor is produced. Experiment system was built for the test of prototype with copper and aluminum starting winding respectively, including the measurement of dynamic speed, starting torque, starting current and lowest starting voltage. The results of simulation and experiment both show that motor with the structure of agnet arrayed modulation is high in sinusoidal degree by its improvement of air gap field and also with the possess of line-start of surface-mounted PMSM. This paper provided correlation theory method and experiment basis for the research and design of line-start PMSM motor with distributed magnet rotor in arrayed modulation.