Patent GB-292172-A (GB)
Title: Improvements in and relating to dynamo-electric machines
IPC: H02K23/42
Filed: 1928-06-16
Abstract: 292,172.. International General Electric Co., Inc., (Assignees of Allgemeine Elektricitõts-Ges.). June 16, 1927, [Convention date]. Exciting; dynamos, regulating; cores. - A continuous-current selfexcited dynamo is adapted to give stable voltage regulation at any flux density down to that due to its residual magnetism by being provided with separate stabilizing windings at some point on the magnetic circuit outside the armature which produce a closed flux separate, from and superposed upon the main flux. This closed flux confers stability and adjustability on the machine voltage during both the period of preliminary excitation by the stabilizing winding alone and the later period when the main windings are operative. The auxiliary flux may, in part, oppose the main flux and may, alternatively, be produced by windings which also produce the main flux. The invention is described in connection with Fig. 1, which shows a pole having main flux windings Aw, and two stabilizing windings Aw2<SP>1> and Aw2<SP>11> wound on portions Qs<1> and Qs<11> of the pole, the. current in the former being fixed in direction so as to give a flux coincident with the residual magnetism of the machine and that in the latter being reversible. It is shown by means of excitation characteristic curves that by controlling the absolute value of the magnetizing force of the windings, the ratio of the magnetizing forces in the two stabilizing coils and the reluctances of the different components of the magnetic circuit. anv stable excitation characteristic may be obtained, as in Fig. 2 (which shows the relationships between gap fluxes and ampere-turns), between the residual magnetism line III and the two normal limiting characteristics I, II of the machine in accordance with the magnetic saturations which may be produced in the different parts of the pole. Over the earlier part of the characteristic, the main winding need not carry current. One of the stabilizing windings may be omitted, giving the construction shown in Fig. 4, and the pole subdivision may be effected as shown in Fig. 6, by a division of the laminµ. An additional reluctance may be given by a gap o<1> in the pole, Fig. 6, or between it and the yoke, Fig. 7. Fig. 8 shows a form in which the stabilizing windings are wound on the normal yoke of a machine which carries the stabilizing flux as shown by dotted lines. The flux due to the main coils (not shown) is indicated by full lines. Such an arrangement renders it possible to convert any finshed machine into a stable one. The stabilizing windings may be connected in parallel or series with the main windings and are excited from the normal armature. In the former case a lever of the regulating resistance of the machine simultaneously cuts out separate resistances in the main and stabilizing circuits during its initial movement and short-circuits the stabilizing coils towards the end. In the latter case it is preferable to keep the stabilizing winding currentless during the initial movement of the lever and short-circuited towards the end, as shown in Fig. 10 in which sand h, indicate the stabilizing and main windings respectively. Specincation 231,490 is referred to.