Patent GB-190404772-A (GB)
Title: Improvements in Controlling Alternating Current Motors.
Filed: 1904-02-26
Granted: 1905-01-19
Abstract: 4772. British Thomson-Houston Co., [General Electric Co.]. Feb. 26. Motors, controlling. -Repulsion motors are controlled by a system whereby the short-circuiting brushes on the secondary member are displaced from the line of magnetization of the primary field and the motors are connected in series to the current supply, after which the brushes are moved step by step towards the line of magnetization ; when the motors speed up, they are connected in parallel, and the brushes are again displaced, after which the brushes are again brought back. In Fig. 5, which shows the circuits for a single car in a train-control system, the motors M', M' are connected by switches A, B, H to the work circuit from the trolley T, and U<1>, U<2> represent devices, shown in detail in Fig. 6, for turning the brushes. The secondary C<2> of a transformer supplies the control current, and the reversing-switch H acts by supplying current to either the right-hand or left-hand taps of the motors M<1>, M<2>, according to which of the strips i<1> ... i<5> ... are under the stationary contacts h<1>; this is determined by the coil F<1>, R<1> which is energized, and in turn depends upon the position of the reversing-switch N. By shifting the connection from one tap to the other the direction of magnetization is varied, and the motors reversed. Similarly, the motors are connected in series or parallel according to the position of the cylinder of the series-parallel switch B. The switches A, B are interlocked, as are also the control and reversing-switches J, N, and with the connections shown the switches B, H do not open under load. If the reversing-switch N is in the forward position, with the contacts F over the stationary contacts o' &c., on moving the controller J into the position 1<x> two circuits are closed from the secondary C<2>, one current flowing through the contacts k<3>, j<2>, and k<8> to the coil S of the switch B, and back to the transformer through the contacts s, k<2>, j<1>, k<1>, and the other flowing through the contacts o<1>, n<1>, o<2> to the coil F<1> of the switch H, and back to the transformer C'. In this position, therefore, the motors are in series to drive forward. On moving the controller into the position 2x, an additional circuit through the contacts k<3>, j<2>, k<4>, b<6>, d<5>, and b<5> to the coil a is closed. The switch A is thereby raised, and the motors connected to the work circuit, and the circuits of the coils S, P are broken, so that any change of the switch B is prevented so long as the main switch A is closed. In the position 3x, the coils v<1> are energized, and the brushes slightly turned, with their carrier 12, by gearing 13, 14, 15, and 16, and in the next position the coils v<2> are energized, and so on, until the motors are at top speed in series. When the position 5<Î1> is reached, the switch A opens, the coils v<1> &c. are de-energized, and the brushes are displaced by springs 19, Fig. 6, and at the position 6<x> the motors are connected in parallel ; further movement of the control J shifts the brushes as before. As shown in Fig. 6, if any of the coils v<1> &c. becomes energized, it is attracted by the backplate of the member adjacent to it, and so shifts the rack and operates the brushes 10.