Numerical Simulation and Experimental Analysis on the AC Losses of HTS Bulks Levitating Under a Varying External Magnetic Field

Abstract

Alternating current (AC) loss occurs when the high-temperature superconducting (HTS) maglev running on a permanent magnetic guideway (PMG) with a varying field. The running stability and safety of the HTS maglev vehicle will be influenced by the AC losses, which are closely related to the magnetic field fluctuation of the PMG and the levitation characteristics of HTS bulks. In order to study the AC losses of the HTS bulk under a varying field with different frequencies and amplitudes, numerical simulation and experimental analysis are employed. The simulation model was built by COMSOL Multiphysics with the partial differential equations module and heat transfer module. The experimental analysis of AC losses was designed based on a calorimetric method. The experiments are based on an HTS maglev dynamic measurement system, in which the rotational velocity of the PMG and working height of the HTS bulks are changed for simulating the experimental conditions of different frequencies and amplitudes of the AC field. And, the AC losses of HTS bulks are deduced from the evaporation amount of the liquid nitrogen. The simulation findings are consistent with the experimental phenomena qualitatively, which not only verify the rules of frequency and amplitude, but also the availability of the numerical simulation method. Moreover, the findings provide important hints for the future design of the HTS maglev systems.