Inverstigations On Vibration Of Axial Flux Permanent Magnet Motors

With the devolepment of permanent magnet material and manufacturing process, axial flux permanent magnet(PM) motors are significantly improved relative to that of radial flux motors. They have many advantages such as simple structure, short axial length, reliable operation and high power-weight ratio etc., finding wide application in high power, high power density and special installation requirements. Since PM motors are of symmetric systems with fluctuating forces, they inevitably produces noise and vibration like the radial one, reducing the performance and even life of motors. This work studies the vibration characteristics of topoloical structure and relationship between basic parameters and transverse forced vibration. Main contents are as follows:This work examines the tooth frequency excitation of axial flux PM motors, by using superposition method, and clarifies the relationships between the slot/pole combinations and unbalanced magnetic pull(UMP) and cogging torque(CT), and then proposes a method for vibration suppression. Based on these results, the effect of slot/pole combinations on the three kinds of force modes has been identified as Axial translational rotational modes(ATR), Radial translational tilting modes(RTT) and Balanced modes(B). Secondly, numerical verification is carried out. The radial, tangential and axial magnetic forces in the airgap are calculated by Maxwell stress tensor method, and the UMF and CT about three axes are obtained via the superposition of their projections. Three dimensional static electromagnetic Finite Element Methods is employed to calculate the UMF and CT, and numerical results are well consistent with the theoretical analysis. Finally, general dynamic model of disk type stator undergoing axial vibration is developed by using Hamilton’s principle, in which stiffness perturbation of magntic force due to rotating magnetic field in the airgap is included. The forced response is examined and results imply that the relationships between parameters such as the length of air, pole pairs, pole-arc coefficient and transverse forced vibration.Main works of this thesis is a part of the National Natural Science Foundation of China(Investigations on Mechanism of Noise and Vibration Reduction of Permanent Motors Based on Phase Tuning, Grant No. 50705062), and a part of the National Natural Science Foundation of China(Dynamic Topology Optimization of Rotational Ultrasonic System, Grant No. 51175370). This work provides a theoretical basis for vibration and noise reduction of the axial flux PM motors.