| Disc type permanent magnet synchronous machine (PMSM) has characteristics such as light weight, small size, compact structure, low moment of inertia, steady running at low speed and so on. It was widely used in many fields, such as numerical control machine tools, robots, electric vehicles, elevators, household appliances, etc. Motor is one source of the noise, whose noise level became a significant index to evaluate its quality and an important factor affects its competitiveness.This issue is from the Innovation Team project of Education Department of Liaoning Province (2006T100). This dissertation concentrates on calculation and suppression techniques of electromagnetic noise of disc type PMSM of six phases, dual-Y and 30 o shifts, and with multi-pole and few-slot, whose purpose is aimed to achieve a more accurate calculation of electromagnetic noise and to provide a definite basis for the design of motors with low noise.The normal electromagnetic force caused by the mutual action of stator and rotor is the main source of motors'electromagnetic noise. On account of the structure characteristics of disc type PMSM of multi-pole and few-slot, six phases, dual-Y and 30 o shifts, this thesis firstly carries out the study on the magnetic field distribution in the air gap. As the stator winding of six phases, dual-Y and 30 o shifts is equivalent to two separate Y connected winding of three-phase, the harmonic distribution of magneto motive force (MMF) in the stator winding of this structure is obtained. When the maximum common factor of overall number of slots and pole pairs is t, the whole winding can be separated into t same units. Study on the unit motor, the magnetic field distribution generated from the permanent magnet with slot in the stator or non-slot in the stator is discussed through analytic method. It turned out that, for the motor with multi-pole and few-slot, six phases, dual-Y and 30o shift, when the pole pairs of unit motor serves as the fundamental wave, there is no harmonics of 5th and 7th order in the MMF of stator winding, and the order of harmonic generated by the permanent magnet in the rotor is decided by the match of the number of poles and slots.The natural frequency and mode of stator system are the main research content on the electromagnetic vibration and noise of motors. According to the stress and vibration direction of stator system in the disc type PMSM, the stator core and the cover of axial-flux inner rotor (AFIR) disc type PMSM is equivalent to an elastic sheet, whose frequency constant of different ratios of inner and outer diameter and different modes of vibration is determined through the software ANSYS. And then, the calculation method of the natural frequency of the stator system is obtained, and the procedure for the calculation of electromagnetic noise is established. Applied the calculation method of inherent frequency on two prototypes of 15kW and 5kW, the data are in good agreement with the experimental results.On the process of calculating the electromagnetic noise of AFIR disc type PMSM, there is a hypothesis that the electromagnetic noise on the cover side is the strongest, and the effect of motor's draw ratio on the distribution of noise is ignored. However, the motor's draw ratio definitely has influence on the noise around the motor. In order to consider the influence of motor's draw ratio, this paper carried out the acoustic field calculation on the AFIR disc type motor with different draw ratios through the software ANSYS, the relationship between the draw ratio and the distribution characteristic of noise is obtained, and the analytic program is corrected accordingly. Finally, through the calculation and analysis, this dissertation provides the suppression measurements of electromagnetic noise of disc type PMSM with multi-pole and few-slot.
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