A superconducting induction motor using double-helix dipole coils

The double-helix dipole configuration, which uses concentric pairs of oppositely-tilted helical windings to generate a dipole field, is the basis of a design for a unique high-torque, low-rpm, compact superconducting motor. We describe an analysis method that uses coupled mutually-inductive equivalent circuits for each phase for computing the performance and operating characteristics of such a device. We discuss the performance and limitations of an example motor that uses NbTi superconducting cables for the stator and rotor. The example device is a 4-pole, 2-phase induction motor that produces typically 10 000 HP for a 1-m effective length rotor with a 0.4 m diameter rotor operating at ∼300 rpm. In addition, the relatively large minimum bend radius of the double-helix coil configuration also facilitates the use of brittle superconducting materials such as HTS or A-15 for this application.