Patent GB-168181-A (GB)
Abstract: 168,181. White, A. E., (U.S. Light & Heat Corporation). June 10, 1920. Exciting.-The generator of a train-lighting system is provided with an auxiliary field winding or windings, an auxiliary brush or brushes and a polarized electromagnetic switch to maintain the polarity of the generator constant when its direction of rotation is reversed. The auxiliary field windings are cut out when the normal cutin switch operates, and are cut in to reduce the generator voltage by means of an ampere-hour meter or a relay when the battery is fully charged. The generator is provided with a field winding to compensate the armature reaction, and this winding may be connected in the lamp circuit to increase the voltage of the generator when the lamps are increased. A generator 1, Fig. 1, is provided with main field windings 2 connected to auxiliary brushes 5, 6 and to a control switch A which varies the direction of the current in the windings 2 according to the direction of rotation of the armature. The generator is also provided with an auxiliary winding 28 and a regulating winding 7 both of which are placed in quadrature with the main windings 2. The control switch A comprises a polarized armature 18 connected to a pivoted insulating-member 17 carrying contacts 19, 20 which engage contacts 12, 13 on a member 11 and contacts 15, 16 on a member 14. A differential ampere-hour meter 34, connected in the battery circuit 30, operates one element 36 of a switch 35, 36 and the usual cut-in switch 27 short-circuits a resistance 29 and the winding 28 when in its closed position. When the car is at rest the parts occupy the position shown and the field windings 28 and 7 are connected in series with the resistance 29 and meter 34 across the battery 30. When the train starts, an electromotive force is developed across the brushes 5, 6, due to the action of the field winding 28 and the main windings 2, and the switch windings 22, 23 are energized by a current the direction of which is dependent on the direction of rotation of the armature. Under these conditions the electromotive force developed across the main brushes 3, 4 energizes sufficiently the polarizing winding 25 of the switch armature 18, thereby operating the member 17 of the switch A to excite the field windings 2 in the proper direction to ensure positive polarity of the brush 3 under both directions of rotation of the armature. When the voltage of the generator reaches a predetermined value the switch 27 closes to connect the generator directly to the load circuit and to short-circuit the resistance 29 and winding 28 if the contacts 35, 36 of the meter 34 are open. A variable regulating winding 7 is provided to compensate for the armature reaction of the generator. When the battery is fully charged the contacts 35, 36 of the meter 34 are closed to connect the winding 28 in series with a resistance 38 and the winding 7 across the generator. The action of this winding decreases the excitation of the windings 2 and the voltage of the generator is reduced in order that the battery 30 may float on the line. In a modification, the ampere-hour meter 34 is replaced by a voltage-relay controlling the circuit of the winding 28. In a further modification the winding 7 is placed in the lamp circuit only, and by its action the output of the generator is increased as the lamp load is increased. In the arrangement shown in Fig. 4, the generator 1 is provided with four poles 44 - - 47, main 'brushes 3, 4, and an auxiliary brush 5<1>. The poles are provided with auxiliary windings 49 - - 52, connected in series with a resistance 48 across the terminals of the cut-in switch 27, and with main windings 53 - - 56, connected in series with the polarizing winding 25 of the control switch A. As shown, the generator armature has just commenced to rotate in the direction indicated by the arrow and due to the excitation of the coils 49 - - 52, currents are developed in the field windings 53 - - 56 and in the windings 22 and 23 of the switch A in the direction indicated by the arrows. An electromotive force is developed across the main brushes 3, 4, the current in the coil 23 is reversed, and the switch A operates to open the contacts 16, 20, the contacts 15, 19 remaining closed. When the voltage across the brushes 3, 4 reaches a predetermined value the switch 27 is closed to short-circuit the windings 49 - - 52. When the battery 30 is fully charged, the contacts 35, 36 are closed to energize the field windings 49 - - 52 in the opposite direction, their action assisting the armature reaction to reduce the generator voltage. In the arrangement shown in Fig. 5, the main brushes 3, 4 are connected to line through compensating windings 59, 60 selectively energized in accordance with the direction of rotation of the generator 1. Field windings 61, 62 and a resistance 48 are connected across the cut-in switch 27. The contact 65 of the contact switch A engages contacts 15, 16 when the generator is at rest, the contact 15 only when the generator rotates in the direction of the arrow, and the contact 16 only when the generator rotates in the opposite direction. The lead 9 is connected through a switch 34, closed when the battery is fully charged, and an adjustable resistance 38 to a. point between the resistance 48 and a field winding 61. When the generator is at rest the resistance 48 and field windings 59 - - 60 are connected in series across the battery 30, the windings 59 and 60 opposing the action of the windings 61 and 62. Upon rotation of the generator in the direction indicated by the arrow a current passes from brush 3 through field winding 59, winding 22 of switch A, contact 15 to spring 65, where it divides, one part flowing through winding 25 and field windings 63, 64 to brush 5<1> and the other part through the winding 23 and field winding 60. The switch A operates to break the circuit of winding 60 at the contact 16, while 59 remains energized to act as a compensating winding to oppose the armature reaction. The operation of the switch 27 short-circuits the field windings 61, 62, which are energized in the opposite direction to reduce the generator voltage by the closure of the switch 34 when the battery 30 is fully charged.