Dual Coil Superconducting AC Homopolar Machine for Turbo-Generator Applications

High-speed, high-power-density generators capable of being directly coupled to a gas turbine engine are needed in the multi-megawatt class for power generation aboard hybrid-electric aircraft and ships. Here we present a homopolar generator concept featuring dual stationary REBCO high-temperature superconductor field coils, one at each end of the machine, and a mass-optimized rotor consisting of discrete pole pieces. The location of the field coils permits easy access for servicing or replacement, and enhances flux concentration along the active length. The design produces a calculated rated power of 5.5 MW with 97.6% efficiency at 8000 rpm, corresponding to a power density of 3.5 kW/kg.