Prediction and experiment of DC- bias iron loss in radial magnetic bearing for a small scale turbomolecular pump

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Iron loss calculation is a crucial part of turbomolecular pump design, since the molecular pump works in vacuum environment and the iron loss eventually transforms into thermal radiation. In this paper, an iron loss prediction model for a radial magnetic bearing of turbomolecular pump considering temperature influence is proposed. A ring specimen test under different dc-bias current, different frequencies, flux densities and temperatures are used to measure iron loss of steel laminations. Then, an iron loss model with variable hysteresis loss coefficients, eddy-current loss coefficients and dc-bias loss coefficients is used for iron loss calculation of the magnetic bearing. Flux densities of different part of magnetic bearing under different working states are obtained by using FEM. Finally, the measurement and subtraction method of iron loss in radial magnetic bearing is proposed, the accuracy the proposed iron loss model is validated by an iron loss test on a prototype of a 300 L/s 36000 r/min turbomolecular pump supported by magnetic bearing.