Patent GB-301953-A (GB)
Title: Improvements in and connected with the automatic regulation of dynamo electric machines
IPC: H02J7/16
Filed: 1927-09-08
Abstract: 301,953. Stone & Co., Ltd., J., and Honey, A. E. Sept. 8, 1927. Exciting. - For automatically regulating the voltage of a dynamo-electric generator in dependence upon the speed a self-regulating auxiliary brush dynamo revolving therewith is connected so as to oppose the flow of current in the exciting circuit of the main generator. As shown applied to an alternating-current train-heating installation. the rotor coils c, c<1> of a two-phase alternator are connected through slip rings d - - d<2> and switches g - - g<3> to heaters h<1> - h<3> The switches g - - g<3> when closed shortcircuit resistances j - - j<3> in the circuit of the field winding a which is fed from a. battery b. Mounted on the shaft of the alternator is a three-brush dynamo k preferably having a toothed ring armature, and having a shunt field winding l and a winding l<1> connected to one of the main brushes and an auxiliary brush n. On the shaft there is also a small centrifugal governor o having movable contact plungers p, p<1> co-operating with fixed contacts q - u. When the train is at rest, the governor parts occupy the position shown, in which position the armature of the regulating dynamo is short-circuited through the contacts q, r and the plunger p. At the same time the alternator field winding a is in a closed circuit with a non-inductive resistance 2 through the plungers p, p' and contacts q - - t. When the train reaches cut-in speed, the plungers occupy the intermediate position shown in full black. In this position the armature of the regulating dynamo is still short-circuited, but the field winding a of the alternator is connected across the battery b through the plungers p, p<1> and contacts q, r, s, u, the non-inductive resistance 2 being cut out of circuit. As full speed is approached, and the plungers reach the positions shown in dotted lines, the short-circuit across the armature k is removed and the auxiliary machine is thus connected in series with the field coil a and in opposition to the battery b, but by reason of the self-regulation of the auxiliary machine, the voltage of the auxiliary machine does not increase in proportion to the speed. An artificial load comprising a calibrating resistance y having a constant temperature coefficient may be connected across the brushes of the auxiliary generator, and, to limit the voltage of the main generator when a few only of the heaters are in use, a switch v<2> normally short-circuiting a resistance z in series with the resistance y is adapted to be opened by a spring acting in opposition to a relay coil v<1> in the main excitation circuit whereby the opposing voltage of the regulating dynamo is increased. To compensate for variations in the voltage of the battery b, a shunt relay coil x<1> connected across the battery acts in opposition to a spring to open a switch x<2> short-circuiting a resistance x in series with the resistance y so long as the battery voltage is normal or below normal, but when the battery voltage is above normal the switch x<2> is opened and the opposing effect of the auxiliary dynamo is increased. Since the centrifugal governor works in two steps, two concentric springs o<1>, o<2> of different strengths may be employed therein. Electromagnetic switch gear may replace the governor, the coils being excited from the terminals of the regulating dynamo which in this case is not short-circuited at low speeds. Specification 281,010, [Class 38 (iv), Electric supply and transmission systems &c.], is referred to.