Investigation On The Electromagnetic Vibration Of Permanent Magnetic Machines Based On Coupled Magnetic Mechanic Method

The electromagnetic vibration and noise, which are considered the main sources of the acoustic noise and vibration of permanent magnet machines, are analysed in this paper. The electromagnetic field, the vibration characteristics and their coupling of the permanent magnet machines are discussed.First of all, an analytical model for the prediction of armature reaction magnetic field in surface mounted permanent magnet machines is developed, which can consider the effects of stator slots and rotor eccentricity. The magnetic field domain in PM machines is divided into three subdomains, which are the air-gap subdomain(including the magnet whose remanence is zero), the stator slots subdomain and the slot opening subdomain. The magnetic field governing equations are firstly built, and the general solutions contain the coefficients to be determined. Then by applying the boundary conditions and interface conditions which are derived by a one-order perturbation method which considers the rotor eccentricity, the coefficients are determined.Secondly, the analytical subdomain model for the prediction of armature reaction magnetic field in surface mounted permanent magnet machines is combined with an analytical model for the prediction of open-circuit magnetic field developed by other people. The combined analytical model the used to analyze the electromagnetic forces in two different types of PM machines, viz. a machine with4poles and24slots, and a machine with8poles and12slots. The distribution of the electromagnetic forces in two condition of no load and load are derived, and the time harmonic components distribution and space harmonic components distribution are derived.At last, two types of coupled magnetic-mechanic analysis method are presented.The weak coupling method is firstly introduced:The Simulink software is used to analyze the control circuit, and the JMAG software is used to analyse the electromagnetic field of the PM machine, and the electromagnetic force of the PM machines excited by the control circuit is acquired by the coupled circuit-field analysis. Then the force is loaded on the3D vibration model to analyse the vibration characteristic of the machine. An interior PM machine with8poles and48slots is taken for example to illustrate the weak coupling method.The strong coupled magnetic-mechanic analysis method is then introduced. This method can consider the mutual influence between the electromagnetic field and the vibration, making the result more accurate. The complete analytical model introduced before and achieved by programming in MATLAB is used to analyse the electromagnetic field, the vibration characteristic is analysed by FE method based on the3D vibration model built in ANSYS. The APDL language is used to call the electromagnetic model and the vibration model, and to build the communication interface between MATLAB and ANSYS software. Then the strong coupled magnetic-mechanic analysis is finally achieved. A machine with4poles and48slots, and a machine with8poles and12slots are taken for examples to illustrate the strong coupling method. The result of simulation in accordance with theory.