Dependency of hysteretic loss on speed and tilt in a rotating superconducting magnetic bearing

Abstract

Abstract Superconducting magnetic bearings enable friction-free rotation, which is beneficial for different applications. Whereas mechanical losses are drastically reduced, additional hysteretic losses might be generated as for example by a process-related tilt of the field-cooled permanent magnet of the superconducting bearing. We designed a caloric measurement setup with a resolution down to 5 mW in order to study such losses in more detail. Therefore, a field-cooled magnet ring is deliberately tilted up to 3° before it rotates with a speed of up to 5000 rpm above the superconducting ring. The generated losses inside the superconductor lead to an increased evaporation rate in the attached liquid nitrogen bath, which in turn results to a measurable volume flow. The determined losses increase almost linear with speed, whereas an exponential increase was observed for the tilt angle. The results were confirmed by 2D simulations using a two-component model leading to similar dependencies for the hystertic losses on speed and tilt.