Large superconducting DC drives with separate torque reaction windings

A slotless-armature DC motor with multiplex winding can be designed for higher power rating compared to one with a conventional slotted armature. Conventional field systems would be very heavy and a superconducting field winding is considered in order to create an iron-free stator and lightweight machine. The superconducting field winding is relieved of reaction torque by means of a special winding attached to a separate torque tube. The reaction winding is also designed to establish the necessary commutation flux in the interpole region. Test results from a small laboratory machine demonstrate the principle of the proposed torque reaction winding. A design for a 20 MW ship propulsion motor is presented.