Patent GB-190223066-A (GB)
Title: Improvements in Systems of Electric Lighting
Inventor: LEITNER HENRY
Filed: 1902-10-23
Granted: 1903-11-19
Abstract: 23,066. Leitner, H., and Lucas, R. N. Oct. 23. Dynamos, regulating; field magnets.-Relates to the lighting of trains by means of accumulators charged by a main dynamo driven at a variable speed, a subsidiary dynamo driven at the same or a proportional speed, being employed to weaken the field or fields of the main generator as the speed of driving increases. This regulation is in the present case assisted by one or more of the following resistances :-(1), one whi3h becomes more conducting as it rises in temperature, and is arranged in series with the shunt or fine wire winding of the subsidiary dynamo, (2), another which becomes less conducting as the temperature rises, and is arranged to be in parallel with the armature circuit of the subsidiary dynamo, and, (3), one, similar to (2) which is in series with the fine wire field winding of the main dynamo and is adapted to be heated by current from the main dynamo flowing through a second resistance placed near to it. The shunt a of the main generator is in series with the wire resistance a<1> and with the series winding d of the demagnetizing-dynamo. The series winding c of the main generator is connected to a wire resistance a<2>. One or more lamp resistances h are placed in the shunt b of the subsidiary dynamo, and a wire resistance i is arranged across the main generator field and armature. The other parts shown are :- Commutators, brushes, and armatures e, f of the main dynamo and demagnetizing-dynamo mounted on the same shaft, the battery g to be charged, and the switch for switching the dynamo into the accumulator circuit. This switch consists of a balanced armature with contact-pieces o, p for bridging the gaps m, n, a high-resistance winding l, a fine-wire winding j, and a low-resistance winding k of the field. When the speed increases sufficiently for current to be generated, it passes through the winding c, the resistance a<2>, and the resistance j, after which it branches, partly passing through the armature winding l and the leads l<1>, l<2> back, and partly passing through the lamp h, the winding b, and so back. The field of the switch and its armature having both been energized, the armature turns against the action of a spring until the gap m is bridged. This only takes place when the electromotive force of the generator is above that of the battery. The current now flows through the winding j to the cells, charging them with a feeble current. As the voltage of the generator increases the armature turns still further till the gap n, n is also bridged. The charging-current now passes mainly through the thick wire k, thereby strongly charging the cells and also strengthening the field of the switch, causing it to act as a holding-down relay. When the main current falls, the beforementioned spring opens the switch. When the voltage of the generator tends to rise too high, sufficient current flows through the lamp h to reduce its resistance, thereby allowing more current to flow through the winding b, which results in the field of the demagnetizer being strengthened and the current in the winding a reduced. On the other hand, if the voltage of the generator falls, less current passes through the lamp, the resistance thereof increases, and the magnetic field of the demagnetizer is also weakened. The wire resistance i acts as follows :-When the generator voltage falls, less current passes through the resistance i, whereby its temperature falls and its resistance decreases, allowing more current to pass through the field winding a. When the voltage increases, the reverse action takes place, so that less current passes through the field winding a. The resistance a<1> acts somewhat similarly. When the generator current increases, it heats the resistance a<2>, and this by radiation heats the resistance a'. The latter therefore diminishes the current in the field winding a. If the generator current falls, the temperature of the resistances a', a<1> falls, and more current flows through the winding d. In cases in which the variations of speed are not extreme, the system of resistances above described may be used alone, the subsidiary dynamo being dispensed with.