Magnetics and Superconducting Coil Design of a 10 MJ, Fast Discharging Homopolar Machine

The design of the magnetic circuit and the superconducting coil of a 10-MJ homopolar machine is presented. The machine is-of the two-rotor drum type releasing its kinetic energy within 30 ms into an inductive load. The rotors' surface speed is 277 m/s. The machine is a model of a l.3-GJ homopolar whose magnetic-circuit conceptual design is also described. The stator of the machines includes highly saturated iron to enhance flux concentration in the rotor and to reduce flux leakage. The flux intercepting the rotor for a given excitation mmf is maximized by variation of the rectangular coil cross-section's linear proportions and the linear dimensions of the discretely placed iron and air portions in the stator. The superconducting coils are designed to be transiently cryostable at an average current density of 40 A/mm2, which means the coil can recover from a localized quench. · They are placed in three chambers filled with liquid helium. All are installed within the outer flux return iron which also serves as the vacuum vessel.Center for Electromechanic