Development of superconducting DC machines at international research & development Co., Ltd.

The entire program of the development of superconducting dc machines at International Research & Development Co., Ltd. (IRD) from 1963 onwards is covered. The early thinking on the choice of the type of machine and the reasons for selecting the homopolar are described; the first 50-hp model motor and the 3250- hp Fawley motor are then discussed. A brief account is given of the testing of the latter both at IRD and Fawley. The bulk of the paper is devoted to an account of the approach to the development of these machines at IRD, concerning principally the areas of current collection, magnetic screening, and terminal voltage, The importance of achieving a high current density in brushes is explained and an account is given of a new method of current collection developed at IRD and is based upon the use of carbon fibers. A brief discussion is made on superconducting windings, refrigeration systems, speed control, and the effects of failure of the cryogenic plant. Finally, reference is made to the superconducting marine propulsion system now under construction at IRD.