Design study of DC motors with high-Tc superconducting field winding

The slotless DC motor with multiplex windings has been designed, constructed and demonstrated at British Rail and UMIST over a period of several years. It can be designed with ratings much higher than is possible with conventional slotted DC motors. However design projections for high power ratings based on the normal type of excitation showed that the field system would be rather heavy. The recent development of higher temperature superconductors might provide a field system of acceptable weight. One of the principle applications for such high power DC motors would be ship propulsion requiring power ratings extending to tens of MW at speeds below 200 RPM. However for an initial demonstration it is necessary to build a small laboratory machine. The paper presents some of the concepts to be incorporated within the proposed laboratory machine which has a projected rating of 9kW. In addition, a design for a 10MW machine is presented and compared with a conventional design