Patent GB-190408403-A (GB)
Title: Improvements in and relating to Alternating Electric Current Motors and Generators.
IPC: H02K19/32
Filed: 1904-04-12
Granted: 1905-04-12
Abstract: 8403. British Thomson-Houston Co., [General Electric Co.]. April 12. Motors, controlling.-Motors, operating synchronously at several speeds and having a good starting - torque and yet operating economically at synchronism, are arranged with the conductors of the windings connected in groups joined to the external circuit, so that the number of poles in both stator and rotor can be varied by changing the external connections and, at the same time, the impressed voltage is varied, and various parts of the winding are connected in series or parallel with regard to the source of alternating current. Fig. 1 shows the connections whereby three speeds may be obtained, and Fig. 2 the developed field winding for such a motor. In the latter, the number of poles is determined by the direction of the current in the various conductors F<1>, F<2>, F<3>, F<4>; with any determined number of sets of poles, in certain conductors the current direction varies in the same sense for all of the predetermined number of poles, and the groups above referred to are obtained by connecting in series the conductors in which the current variations are identical, and the terminal connections of the groups are varied to vary the number of poles. In the motor shown, twelve, six, or eight poles may be produced by joining d' and d<3>, or d' and d<4>, or the pairs made by joining d' and d<4>, and d<2> and d<3>, to the source of current. In the position 1 of the controller, Fig. 1, the current path is from the lead a<1> through the contacts c<1>, c<3> and rectangle A<1> to the contact c', where the current divides, part going to the contact c'‹, rectangle A', and contacts c<9>, c<7>, and thence to the lead a<3>, and the remainder passing through the rectangle A<3> and contacts c<15>, c<13> to the lead a<3>. The conditions resulting are shown in Fig. 1 x, and the field F, being short-circuited through the rasistance r, acts as the secondary of an induction motor. To improve the starting-torque and to prevent hunting, a squirrel-cage winding E, Fig. 2, is introduced. In the position 2 of the controller, the armature connections are unchanged, but the field is short-circuited through the resistance R in parallel with the resistance r. The resistance R is gradually cut out as the controller is moved, till at the position 5 the field is connected to the source of direct current f<2>, f<1>, as shown in Fig. 5<x> ; to increase the efficiency, the resistance in series with the field is cut out, the impressed voltage is increased, and the armature changed from Y to delta connections. In the position 7, the armature is connected in Y again, but the halves are connected in parallel, which thus corresponds to the eight-pole arrangement described in Fig. 2. As the controller is again moved, the armature speeds up, till, at the position 10, the fuel F is again connected to the leads f<1>, f<2> with resistance in series. At the position 11, the armature is again changed to delta, the resistance is out out, and the position fur second synchronous speed is obtained, At the next position, the armature is again connected in Y, and the changes go on as before till, as shown in Fig. 15<x>, the armature is in delta, and the final position for third speed is reached. The invention may be applied to dynamo-electric generators.