Homopolar DC motor and trapped flux brushless DC motor using high temperature superconductor materials

Two motors have been designed and built for use with high-temperature-superconductor (HTSC) materials. They are a homopolar DC motor that uses HTSC field windings and a brushless DC motor that uses bulk HTSC materials to trap flux in steel rotor poles. The HTSC field windings of the homopolar DC motor are designed to operate at 1000 A/cm/sup 2/ in a 0.010-T (100-G) field. In order to maximize torque in the homopolar DC motor, an iron magnetic circuit with small air gaps gives maximum flux for minimum Ampere turns in the field. A copper field winding version of the homopolar DC motor has been tested while waiting for 575 Ampere turn HTSC coils. The trapped flux brushless DC motor has been built and is ready to test melt textured bulk HTSC rings that are currently being prepared. The stator of the trapped flux motor will impress a magnetic field in the steel rotor poles with warm HTSC bulk rings. The rings are then cooled to 77 K to trap the flux in the rotor. The motor can then operate as a brushless DC motor.