Superconducting DC Machines

  • A. D. Appleton
Part of the Nato Advanced Study Institutes Series book series (NSSB, volume 1)


A rotating electrical machine may be manufactured in a few minutes using some copper wire, a battery and a few odds and ends. However, when the power required from a machine is increased, more sophisticated methods are necessary and ultimately the available technology is pushed to its limits. For large direct current motors and generators, the subject of this paper, the limit of power using the conventional design approach is around 10 MW or so and, of course, the use of iron magnetic circuits is essential (we shall see later how essential is the iron if normal temperature materials are employed). The magnetic flux density in the iron may be between land2Tesla depending upon the selected machine geometry, and certainly flux densities much below this level are not much use for rotating electrical machines. It is for this reason that the early superconductors (type 1 superconductors) were of only academic interest to machine designers; the best of them is niobium with a practical working level of less than 0.2 Tesla. It is this fact which explains the absence of superconducting machine development from that historic day in 1911 when superconductivity was discovered to the mid 1960’s when the first machine (in the power range) was manufactured. Superconducting machines became possible with the development of type 2 superconductors, initially with niobium-zirconium, now with niobium-titanium and perhaps in the future niobium-tin. The potential of superconductors to electrical engineers is graphically illustrated in Fig. 1 which compares the current carrying capacities of copper and niobium-titanium.


Model Motor Super Conducting Current Collection Torque Reaction Armature Current 
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Copyright information

© Plenum Press, New York 1974

Authors and Affiliations

  • A. D. Appleton
    • 1
  1. 1.International Research and Development Co. Ltd.Newcastle Upon TyneEngland

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