Fractional Modeling and Analysis of Inductance for Thrust Magnetic Bearings

Thrust magnetic bearings (TMB) are typically of solid structure, with windings wound around. There is prominent eddy current effect, which results in frequency-varying inductance of the TMB winding. The traditional models cannot accurately describe the time-varying characteristics of the TMB coil. Considering the eddy current effect can improve the accuracy of the model, but there are still nonlinear factors, which still make it difficult to accurately describe the response of the system over the full operating frequency range. Therefore, this paper proposes a modeling method for the TMB Inductance based on fractional order elements, and the fractional order TMB model is established using parameter identification methods based on the measured TMB inductance and resistance values to tackle the nonlinear factors. The accuracy of the model is verified by simulations and experimental tests with current ripple under different switching frequencies.