Patent GB-280624-A (GB)
Title: Improvements in or relating to dynamo electric machines
IPC: H02K23/20
Filed: 1926-08-16
Abstract: 280,624. Charlet, H. Aug. 16, 1926. Exciting; commutating-poles and windings. - An interpole machine capable of giving constant, increasing or decreasing volts with increase of speed has on the interpoles Wp, Fig. 1 (i) a winding E excited from a constant source, (ii), a series winding G excited from the main brushes 2. 2 and opposing the winding E and (iii) a compensating and commutating winding H, while auxiliary brushes 1, 1 under the main poles Hp and in quadrature with the brushes 2 are either short-circuited or used for exciting additional coils JK' on the main poles or on the interpoles or on both. The ratio of the main and counter ampere-turns E, G determines the characteristic of the machine. When the brushes 1, 1 are short-circuited, the limbs of the poles Hp are omitted and the shoes are seated directly on the yoke. Fig. 6 shows a form in which both main and interpoles carry coils JK<1>, JK<2> connected between the brushes 1, 1 and counter-windings G, G' connected between the brushes 2, 2. In this case, the use of an external source for the constant excitation coils E is unnecessary, the main brushes 2, 2 serving as the constant voltage supply at all speeds. By the use of a second winding and commutator the machine may be made to give another voltage, for example where a constant voltage network has to be fed and a battery charged simultaneously, as in the case of a train-lighting set. Fig. 7 shows a doublywound machine (without the interpole windings) in which the brushes 3, 3 of the second armature a give a voltage increasing slowly with speed and providing with the main brushes 2, 2 a 3-wire distribution having constant volts on one side and volts increasing slightly with speed on the other. By placing brushes on the armature a collinear with the brushes 2, 2, a 3-wire system is obtained in which the volts on both sides have the same relation with regard to speed as exists at the brushes 2, 2. Windings connected hetween the brushes 3, 3 may be placed on the main or interpoles or both, these windings being connected in series or in parallel. The pairs of brushes 1, 1, 3, 3 or 2, 2, 4, 4, Fig. 13, may be connected in parallel, as shown, or variant connections may be used, e.g. the brushes 1, 1 seriesconnected with 3, 3 and short-circuited. A rising volt-speed characteristic may be obtained without the use of a second armature by inserting resistance in the primary field circuit, for example by arranging the main switch so that when thrown over to battery charging it includes resistance in the circuit of the counter-windings and cuts it out when thrown to the constant-volt supply position. Also, the constant voltage characteristic may be obtained by including a stationary resistance w, Fig. 17, between the brushes 4, 4 of the second armature winding or the brushes 2, 2 when no second winding is used. To make a machine of this type run as a motor, the windings on the main and interpoles are connected with the brushes 2, 2, Fig. 14, and the resistance or short-circuit between the brushes 1, 1 or 2, 2 is suppressed. With a main pole winding JK<1> connected across the brushes 2, 2 a shunt motor is obtained and if in place of the winding Jk<1> a main pole counter-winding connected across the brushes 2, 2 be employed, a series machine results. Fig. 18 shows a doubly wound machine suitable for starting the engine of a car and lighting. The main armature supplies, say, 12 volts and the auxiliary one 4 volts so that the lamps are fed by the 12 volts and the battery and the two armature voltages are added for charging. The auxiliary armature gives the low voltage strong starting current (this connection is illustrated in the Specification) as a series or compound machine. In any of the machines described, the compensating and commutating windings H, Fig. 1, may be extended to the centres of the main poles and embrace the whole armature circumference, as at H<1>, Fig. 20, the portion H on the interpoles acting as commutation windings.