Electromagnetic Field Analysis Of Active Magnetic Bearings And Eddy Current Power Research

This paper is mainly to study the influence of the rotor speed and the conductivity of the rotor material on flux distribution in radial Active Magnetic Bearing(AMB), and to calculate the eddy current losses in the rotor.Due to its precision and directness, the analytical model can be used to common AMB's theory research. The research of the 2D distribution of the flux is based on the Yoshimoto model, on the condition that the magnetic permeability is same and constant in all directions, and neglecting the influence of the rotor eddy current on the flux distribution of the stator's magnetic pole.The flux distribution in a rotor is analyzed quantificationally when it is running at a constant speed. And the variation of the radial and tangential component of the B is studied when rotor rotates at a varying speed. Based on these studies, the rotor's eddy current losses stimulated by a harmonic of the magnetomotive force are estimated.The 2D electromagnetic field in laminated rotor is analyzed by introducing a simplified magnetic vector potential. The flux distribution is observed with the rotor running at varying speed. A graph shows the variation of the eddy current losses in the rotating laminated rotors which are made by materials of different performance parameters.All the research mentioned above are carried out based on the assumption that the magnetic permeability of the rotor material is linear to H in all directions, and its result can be used to optimize the AMB structure. However, in some special circumstance, the anisotropy of the rotor's material must be taken into account when rotor's eddy current losses are calculated, and the axial leakage can not be neglected ether. So the Yoshimoto's model is not compatible any more. To solve the problem, a discrete equation of the flux distribution is acquired by Galerkin's method, and the rotor's eddy current losses is evaluated by 3d FEM , and the results coincide with the ones given by literature.The transient flux distribution is simulated by soft of Maxwell, during the period that the rotor changes from the state of suspended static to the state of running at a constant speed, a phenomenon of B lag of H is observed during the simulation.The calculation of the analytical model is mainly carried out by Matlab, and the detail on models is attached in appendix.