Research On Eddy Current Losses In Radial Magnetic Bearings Based On ANSYS

In vacuum, the power losses in magnetic bearing are consist of: copper loss and iron loss (hysteresis power losses, eddy current losses).Power losses have some influences on the stability and dynamic characteristic of magnetic bearing: At first, in large-scale compressor and motor adapting magnetic bearing, large power losses will make masses heat may decrease the gap between rotor and stator, even make the stator contact the rotor. As for insulating material, it will age rapidly when the working temperature is higher than the limit temperature. So masses heat due to large power losses will decrease the stability of the system. Secondly, large power losses will make the rotor expanded and the temperature excursion of sensor. The temperature characteristic of sensor influence the precision of measured displacement, the precision of measured displacement directly influence the precision of control system, and the precision of control system will further influence the dynamic characteristic of magnetic bearing. Because power losses have deeply influence on magnetic bearing, the research on power losses is a pressing problem to be solved.The main tasks of this paper are as following: (1) The paper discusses the FEM of analyzing electromagnetic field and the cause of hysteresis power losses and eddy current losses, analyses the eddy current losses in single silicon sheet; (2) The distribution of electromagnetic field is the main part in the research of magnetic bearing. The magnetic field is the bridge between the current and force, the amplitude of current directly influenced the amplitude of electromagnetic force and characteristic of magnetic bearing, and the relationship is realized by magnetic field. The paper simulated the magnetic field of radical magnetic bearing of coupling experiment platform and measured the distribution of radical magnetic bearing of coupling experiment platform; (3) Adapting harmonic method of ANSYS to calculate the eddy loss of magnetic bearing, studied the relationship between the control current and the eddy loss, the influence of skin effect and magnetic saturation on eddy loss. The paper analyses eddy current losses in the alternating pole (NSNSNSNS) configuration and paired pole (NNSSNNSS) configuration in radial magnetic bearing.The research indicates that the eddy current losses of radical magnetic bearing is related to the amplitude and frequency of the coil current, distributing of the magnet pole, in the meanwhile ,which is influenced by the skin effect and magnetic saturation.