Impact of vibration-induced disturbances on superconducting magnets
Scholle, Elizabeth Ann
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Permalink
https://hdl.handle.net/2142/19266
Description
Title
Impact of vibration-induced disturbances on superconducting magnets
Author(s)
Scholle, Elizabeth Ann
Issue Date
1995
Doctoral Committee Chair(s)
Schwartz, Justin
Department of Study
Nuclear, Plasma, and Radiological Engineering
Discipline
Nuclear Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Mechanical
Engineering, Nuclear
Physics, Electricity and Magnetism
Language
eng
Abstract
In magnetic levitation (maglev) systems, the interaction between the superconducting magnets (SCMs) and the discrete ground coils causes electromagnetic and mechanical vibrations. These disturbances limit the performance of the maglev, as occurred in the Japanese MLU002 maglev. Here I examine how the electromagnetic oscillations are translated into mechanical vibrations and the subsequent effects on thermal stability.
Dynamic circuit theory is used to determine the harmonic forces on the SCM. The levitation, guidance and propulsion forces are represented by the summation of steady state forces and an oscillatory component due to the ground coils being discrete. The oscillatory component drives the vibrational response. Normal mode analysis is performed to determine the transient and steady state motion of the conductor. The energy dissipated within the conductor due to hysteretic and viscous damping is then determined from the conductor displacements. This energy forms the input to a two-dimensional, transient, thermal stability analysis.
The results from the analysis methods described here have been qualitatively compared with experimental results obtained at the Japanese Railway Technical Research Institute's vibration test stand. Results indicate excellent qualitative agreement in functional form.
Results show how variations in the mechanical properties of the conductor affect the stability of the MLU002 as a function of velocity. It was found that the vibrational resonances occur at certain combinations of Young's modulus and vehicle velocity, quenching the magnets.
The use of high temperature superconductors has also been explored. The strains induced by the vibration of the conductor are detailed. Provided that the resonances can be avoided, the strains experienced by the conductor should not be problematic. The use of cryocoolers operating in the range of 20-40 K is also shown to be possible for maglev applications.
The ability to predict the velocity at which resonances, and hence quenches, occur allows future maglevs to be designed to avoid such quenches by shifting the critical velocity above that intended for operation. An example of this is shown, using system parameters from the design of the new Japanese maglev test facility in the Yamanashi prefecture.
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