Application of Electromagnetic Shunt Damper to Subharmonic Resonance of Superconducting Magnetic Levitation System

Abstract

This study investigates the effectiveness of the electromagnetic shunt damper for reducing the amplitude of nonlinear resonance of a superconducting magnetic levitation system by numerical calculation. An electromagnetic shunt damper, a type of dynamic vibration absorber, can suppress mechanical vibration of the main system by converting a part of its vibration energy into electric energy of a subsystem consisting of an electric circuit. Since the electromagnetic force caused by superconductors has nonlinearity, complicated nonlinear resonance can occur in the superconducting magnetic levitation system in addition to its main resonance. This study especially focuses on 1/2-order subharmonic resonance, which can generate a larger vibration component at half the excitation frequency. Numerical calculations were carried out to examine how two types of electromagnetic shunt dampers consisting of LCR series and parallel circuits can effectively suppress this nonlinear resonance. As a result, it was confirmed that the parallel type electromagnetic shunt damper is more effective in reducing the amplitude of the subharmonic resonance than the series type, even under the condition of a larger excitation amplitude.