In the JR Maglev system, trains are operated by the electrodynamic force between ground coils and on-board superconducting coils (SC-coils). When a train runs, SC-coils are vibrated by the electromagnetic disturbance, which occurs when the train passes over ground coils. Such a phenomenon generates a frictional heat in the SC-coil. It has been surmised that the frictional heat is caused by the relative microscopic slips between structural components of the SC-coil. The purpose of this study is to elucidate the mechanism of frictional heating inside the SC-coil, and to reduce them. A fretting test was performed at liquid-helium-cooled boundaries between the structural components of the SC coil. The test results demonstrated that frictional heating had occurred at the boundary between a epoxy-impregnated SC-coil and coil fasteners. Furthermore, a method to reduce the frictional heating inside the SC-coil was considered by using a correlation between hardness of the frictional surface and amount of the heating. Then, an effect to reduce the frictional heating was demonstrated by liquid-helium-cooled fretting test.

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