Researches On Behavior Of Vibration And Noise In Axial Flux Permanent Magnet Motor

Researches on behavior of vibration and noise in axial flux permanent magnet motor are conducted in this dissertation. The main research contents are as follows.Firstly, axial fluctuating electromagnetic forces caused by various harmonic magnetic fields in air gap are analyzed and calculated for 5kW axial flux permanent magnet motor for boat. Because the axial electromagnetic force created on stator teeth in air gap magnetic field is the main reason for electromagnetic noise and vibration in axial flux permanent magnet motor, axial magnetic flux densities are extracted in electromagnetic field analysis. The axial electromagnetic forces in the air gap are calculated by Maxwell stress tensor method and the harmonics of the force density are also analyzed. Distribution of 3-D magnetic density of axial flux permanent magnet motor is obtained by calculating 3-D magnetic field. 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 power angle. The principle resulting in axial electromagnetic force in axial flux permanent magnet motor is deduced by numerical algorithm.Secondly, according to loading condition obtained by analysis of electromagnetic field, the structure transient response of axial flux permanent magnet motor is analyzed. The axial electromagnetic force acting on stator tooth obtained by calculation of motion electromagnetic field is applied to 3-D model of axial flux permanent magnet motor. The displacement response of all nodes is obtained by transient analysis of 3-D structure for the motor. Modal analysis in structure of electrical motor is an important method to determine whether the resonance of the structure can be induced under axial electromagnetic force. Some modal frequencies and shapes of 5kW axial flux permanent magnet motor are calculated by 3-D finite element method. The improved scheme is presented in structure of the motor.From experimental investigation of axial flux permanent magnet motor, the relationship between axial electromagnetic force and vibration modal frequencies is examined, and the relationship between axial electromagnetic force and electromagnetic noise frequencies is determined, too. It, theoretically and experimentally, draws the conclusion that the axial electromagnetic force frequency is a main factor affecting upon sound radiation of axial flux permanent magnet motor.