Further Studies of a Low-Melting Point Alloy Used in a Liquid Metal Current Collector

Low-melting point bismuth-based alloys are potential replacements for NaK78as liquid metal slip ring material because of their lower reactivity and potentially greater hydrodynamic stability. This paper describes experiments of one such alloy in a model of a 300-kW superconducting homopolar motor using close clearance braid-type collectors. Slip ring tip velocities varied from 5 to 20 m/s and currents ranging from 500 to 2500 A. Viscous power losses tend to follow a simple turbulent model. In all, the data supports the use of low-melting point alloys (LMPA) us an alternative to NaK78.