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Analysis to the Forced Vibration of a High Temperature Superconducting System With Hysteresis

Dynamic behavior with the hysteresis of the levitation force of a high temperature magnet-superconductor system is investigated with application of a displacement harmonic excitation. The dynamic characteristics of the transient stage and the steady stage of forced vibration of the system are discussed in detail. The period-doubling and the natural frequency components are found in forced vibration. It means that the initial frozen magnetic field in superconductor plays an important role on the vibration response. The vibration amplitude vs. excitation frequency is presented. A transition excitation frequency with triple natural frequency is given to distinguish the range of vibration center. The vibration amplitude of the superconducting levitation system shows a linear increasing with the excitation amplitude, which is found to be independent on the critical current density with considerations based on the Bean's critical model. However, the critical current density greatly affects the location of the vibration center. The critical excitation amplitude vs. the field frequency to the superconductor is presented. Levitation is stable most when the sample is exposed to a low-frequency field. In this case large amplitude of the alternating field is needed to break-off of the sample.