Homopolar motor technology development

Homopolar motors are compact and, therefore, are attractive for use in a direct electric drive for a ship. The critical components for the motor are the brushes, the superconducting coils, and the power conversion system to produce the high current, low voltage DC required for the motor. A program is underway at General Atomics for the Office of Naval Research in which a 500 kW Test Stand Motor and a 3.7 MW Motor are being built for demonstration of the technology. The Test Stand Motor will use one superconducting coil and about 25% of the copper fiber brushes needed for the 3.7 MW motor. The latter will use the rotor from the Test Stand Motor, a full complement of brushes, and two superconducting coils. NbTi superconducting coils are being used, but the design allows for a direct transition to high temperature superconductors when it is cost effective and practical to do so. Selected features of the test facility and designs for both motors are discussed together with projections for motors at the 19 MW level in terms of size and weight.