Research On Permanent Magnet Synchronous Motor With Pole Width Modulation Composite Rotor

Surface permanent magnet synchronous motor has been widely used with simple manufacturing process, low cost, energy efficient features. However, surface permanent magnet synchronous motor flux density waveform can be approximately simplified as a flat-topped wave rather than the sine wave which is different from the induction motor flux density waveform. This is equivalent to introduce a large number of harmonics, , sinusoidal waveform level of generally input signal power is high, cause harmonic additional losses of motor increased, and affect efficiency, fail to reflect the energy efficiency of permanent magnet synchronous motor; In addition, the surface of traditional rotor can not be placed starting winding, the motor is difficult to achieve line-start, limiting the promotion and application of surface permanent magnet synchronous motor.Here start from the pole width modulation principle, improve the permanent magnet motor flux density waveform by dividing the rotor pole into some identical amplitude and varying width permanent magnet arrays, and arranging them according to the modulation, then the air-gap flux density waveform of traditional surface permanent magnet motor will close to sine wave, thereby increasing the sinusoidal of flux density, thus improving the performance of the motor.First of all, through theoretical analysis and calculation give out the general formula of magnetic modulation and schemes, according to the pole width modulation principle. Secondly, start from an important parameters called no-load EMF which is closely related to the motor air gap flux density, establish different pole models, analysis the influence to waveform distortion when air-gap flux density changes, and determine a practical 5 pole program; solve the pole width modulation-type permanent magnet synchronous motor no-load EMF and cogging torque data, then the pole width modulation rotor structure can inhibit the permanent magnet synchronous motor no-load induction potential harmonic and weaken the cogging torque comparing with traditional surface rotor structure. Again, produce prototype under the program, to verify the pole width modulation-type permanent magnet motor inhibits no-load EMF waveform and the cogging torque, the consistency of experimental and simulation data proves the theoretical analysis. Finally, use electrical materials of copper and 1J66 as the rotor pole jacket respectively, and make the no-load EMF and cogging torque of the motor are further weakened by improving the motor magnetic circuit, then use 1J66 and NdFeB permanent magnetic materials to constitute the composite rotor of permanent magnet synchronous motor, and simulation analysis of surface-mount pole width modulated composite rotor permanent magnet synchronous motor line-start performance.