Patent GB-191125109-A (GB)
Title: Improvements in Apparatus for Automatically Maintaining a Uniform Load on the Prime-mover of an Alternating Current Generating Set.
IPC: H02J7/34
Filed: 1911-11-11
Granted: 1912-11-11
Abstract: 25,109. Lancashire Dynamo and Motor Co., and Siddeley, H. C. Nov. 11. Equalizing load on prime mover.-To equalize the load on the prime mover of an alternator subject to varying loads, a direct-current machine coupled to the alternator and connected to a battery is provided, the excitation of this machine being caused to vary in accordance with the load on the alternator in such a manner that, on the occurrence of high loads, the machine runs as a motor to assist the prime mover, and on the occurrence of low loads, it runs as a generator to charge the battery. In the arrangement shown in Fig. 1, a prime mover A, an alternator B, a directcurrent machine C connected to a battery F, an exciter D for the machine C, and an exciter E for the exciter D and alternator B are mounted on a common shaft. A resistance d<5> in the circuit of the field winding d<4> of the exciter D, or in the field c<4> of the machine C when no exciter is provided, is controlled by a solenoid g<3>, against the action of a counterweight h', in accordance with the strength of current in the mains G. When the load on the mains G fall below the normal, the decreased action of the solenoid g<3> causes the resistance d<5> to be decreased, thereby increasing the excitation of the exciter D and consequently the excitation of the machine C, so that the machine C runs as a dynamo to charge the battery F. When the load on the mains G increases above the normal, the increased action of the solenoid g<3> decreases the excitation of the exciter D, and conseqnently that of the machine C, in which case the machine C runs as a motor to assist the prime mover A. When it is desired to control the excitation of the machine C in accordance with the state of charge of the battery F as well as the load on the main G, an additional winding f<1>, Fig. 2, connected across the battery F is provided, this winding being arranged to act in opposition to the winding g<3>. The excitation of the alternator B may also be controlled in accordance with the state of charge of the battery by providing its exciter E with an additional field-winding e<5> connected across the battery. In a modification of this arrangement, the winding f<1> is replaced by a winding c<5> on the machine C or on the exciter therefor. The exciter D would, in each of the modifications, be provided with a field winding connected across its brush. In the modification shown in Fig. 3 the exciter D and the fieldwinding c<4> of the machine C are placed in series across the terminals of the machine C, and the polarity of the exciter D is reversed in accordance with the load on the mains G and the state of charge of the battery, by means of two opposing field-windings p, n and a resistance q. The alternator B is also excited by the potential difference between the exciters D, E, as these machines are connected in series across the brushes b<3>, b<4> of the alternator. In the modification shown in Fig. 4, the electromotive force of the exciter D is regulated and reversed by means of a rheostat R, the position of the arm H of which is controlled by windings f<1>, g<3>.