Dynamic levitation behavior of a radial-type SMB under axial load condition

•Under a constant axial load, the axial levitation force and displacement vary in a similar form of dynamic variance. Both of them fluctuate sinusoidally: the period keeps constant, while the amplitude decays gradually to be stable.•Even though the steady-state average of axial levitation force equals the constant load, both the load size and the initial velocity drift the work point of the PM rotor.•Subjected to the sinusoidal load with different frequencies, the axial levitation force and the axial displacement present a complex variation rule and no longer sinusoidal law, because of the superposition effect of the natural frequency of SMB and the sinusoidal load frequency. Due to the external disturbances or the time-variable load, it is necessary to study the dynamic levitation behavior in order to guarantee the stable levitation of superconducting magnetic bearing (SMB). This paper investigates the dynamic levitation behaviors of a radial-type SMB under axial load condition. By adopting the Power-law E-J relation, the simplified H-formulation finite element model of a radial-type SMB was established to calculate the axial dynamic levitation behavior with the aid of the PDE module and ODE module in software COMSOL. The experimental measurements of the axial levitation force were performed in the field cooling condition so as to validate the model. Then, the dynamic levitation behaviors of the radial-type SMB were discussed when the PM rotor suffers from the external disturbances including the axial constant load with different initial velocities and the sinusoidal time-variable loads. The results show that both the load size and the initial velocity drift the work point of PM rotor. And the sinusoidal load leads to a complex time-evolution of the levitation behavior. The study is useful to predict the effects of external disturbances on the dynamic levitation behaviors in the practical applications of the SMB.