Researches On Behavior Of Vibration And Noise In Permanent Magnet Synchronous Motor

The researches on vibration and noise of electrical motors stemmed from the 1940's. The main work oriented towards induction motors, synchronous motors and DC motors. Since Rare Earth Permanent Magnet Synchronous Motor (PMSM) is a new and developing high efficiency special electrical motor, at present, the total and systematic researches on vibration and noise of the PMSM are still rather rare. The problem of vibration and noise of the PMSM have been a difficult dilemma. It becomes a key factor of stable running of PMSM and bottleneck of meeting standard of PMSM when the vibration and noise is serious. Therefore, the researches on vibration and noise of the PMSM can solve the key technology, promote the development of science, technique, economy and society, and expedite the increasing of GDP.The work of this dissertation about researches on vibration and noise characteristics of PMSM includes calculation of damped critical speed of anisotropic supporting rotor-bearing system of the PMSM. Transfer matrix adding time factor is founded and calculated with shifted QR algorithm. As the whirling of the rotor of PMSM directly produces dynamic off-center of the rotor, it results in unbalancing magnetic traction, further influencing the critical speeds of the rotor and increasing dynamic off-center of the rotor. Therefore, the calculation of critical speed of anisotropic supporting rotor-bearing system of the PMSM is a typical mechanical and electrical coupling problem.By means of 2-D motion electromagnetic field calculation of dynamic off-center of rotor in PMSM on load, it shows that magnetic flux density waveform in the air gap relates to magnet configuration, current harmonics, wound distribution, the number and formation of tooth slot of stator and rotor and power angle. It is found that magnetic flux density waveform in the air gap varies from rectangular to approximately sinusoidal waveform when the rotor position changes from direct axis at no load to quadrature axis at load with power angle and phase current increasing. According to radial electromagnetic force calculation and harmonic analysis by numerical method, principle resulting in radial electromagnetic force in PMSM is deduced.Modal analysis of stator of electrical motor is an important method to determine whether the resonance of the stator can be induced under electromagnetic forces. Various order modes of the stators of 1 lkW PMSM and 9.5kW PM servomotor for elevator are calculated by 3-D finite element method. Furthermore, all nodal displacement, velocity and acceleration response can also be calculated if the radial electromagnetic forces act on the model. It establishes fundamental for research on relationship between vibration modal orders and sound radiation ratio and prediction of vibration and noise.From experimental investigation of PMSM, the relationship between radial electromagnetic force and electromagnetic noise frequencies is determined on dynamic off center rotor condition. It, theoretically and experimentally, draws the conclusion that the switching frequency of pulsewidth modulation (PWM) current from inverter is a main factor affecting upon sound radiation of PMSM in servo system of permanent magnet motor control.