| 摘要 |
1,126,968. Dynamo-electric machines; rectifiers. SIEMENS-SCKUCKERTWERKE A.G. 17 Dec., 1965 [18 Dec., 1964; 1 April, 1965; 15 April, 1965], No. 53723/65. Headings H2A and H2F. Commutation in a superconducting D.C. machine or A.C. to D.C. converter is achieved by making each armature coil partly of a material having a sufficiently low critical field to be rendered normal by the working field of the machine so that each coil is rendered alternately resistive and superconductive by the passage of the field which generates the induced E.M.F. As shown, sections 11 of armature coils 2, 3, 4 and 5, are sequentially made normal by the pole flux to prevent reverse flow of current from the active coils through the bus-bars 6, 7. By this means, the negative half-cycles are suppressed. The sections 11 may (Figs. 2a, 2b, not shown) be on opposite sides of a single coil having two turns. These turns may be spaced by one pole-pitch (Fig. 4, not shown), and the leads 6, 7 may be at opposite ends of the machine (Fig. 5, not shown). The coils may extend over axially spaced poles which are staggered and of opposite polarity (Fig. 6, not shown). A single coil may be arranged to carry current in both directions (Figs. 7, 8, 9, not shown), by providing it with two circumferentially spaced parallel connected switching paths 11 which operate alternately. Each coil may have several turns, and it is described in Fig. 11 (not shown), how superconductive layers (18) may lie between plastics layers (19) and between copper foils (17) which act as the switching paths. The machine may be of cylindrical or planar air-gap type (Figs. 12, 13, not shown) and special commutating poles may be provided to give loss-free commutation (Figs. 14-18, not shown). Commutating voltage may be injected by self-saturating chokes on each coil (Figs. 20, 21, not shown), A rotating-field converter is shown in Fig. 22. The switching paths may be superconductors such as lead, niobium, or alloys of lead-bismith, niobium-tantalum or molybdenum-rhenium, and one less than 10<SP>-5</SP> cm. thick. The rest of the windings are of alloys which remain superconductive in the working field such as niobiumzirconium, titanium-niobium, niobium-tin, or vanadium-gallium. |
