GB190304533A - A New or Improved Method of Regulating the Voltage of Alternating and Continuous Current Generators by Means of Alternate Current Excitation. - Google Patents

Abstract

4533. Crompton & Co., and Goldschmidt, R. Feb. 26. Dynamos, regulating.-Relates to a method of regulating a direct-current dynamo by the use of an alternating current in a compounding field coil, and to the application of such a dynamo as the exciter of a self regulating alternating-current generator or alternator in which the voltage rises as the current drawn off increases. If the dynamo is worked at about the "knee" of its characteristic as regards the shunt or ordinary field coil, and if the exciting power of the alternating current in the compounding-coil S2 is less than that of the current in the shunt coils S1, the dynamo voltage is pulsating and unidirectional, and varies, in its mean value, inversely as the compounding-current. The pulsating voltage is rendered practically continuous by the use of a choking-coil D in series with the dynamo, and is regulated by varying the compounding-current. In the application of a dynamo B, regulated in this manner, as the exciter of an alternator A, the alternating current for the compouuding-coil S2 is the resultant of two opposing voltages, drawn from a resistance R in series with the alternator A and a transformer T placed across the alternator terminals. The "resistance voltage" is normally less than that of the transformer T, but increases with the alternator current until this current is a maximum, when the voltages neutralize each other. The current in the coil S2 thus varies inversely as the alternator current, so that the dynamo current which excites the alternator increases with the alternator current. The opposing voltages may otherwise be taken one from a series transformer, replacing the resistance, and the other directly from the alternator terminals. The same result is obtained by the use of two compounding-coils S2 in parallel and in series respectively with the alternator. The compounding-coil may be wound on the same part of the dynamo field magnets as the shunt coil, or on the yoke part. In the case of multiphase alternators, multipolar exciters are employed, the compounding-coils carrying the different phases of the alternating current being wound between the several pairs of poles. Small alternators may themselves be wound with the compounding-coils, but with this arrangement a superposed voltage of double frequency is obtained. When several alternators are excited by the one dynamo, the regulation is obtained by the use of auxiliary compounded dynamos in series with the main exciting-circuit and each arranged to regulate the corresponding alternator. Instead of compounding the dynamo as described above, it may be driven by a continuous-current motor having a compounding coil fed by the alternator current; an increase in the alternator current then increases the motor speed, and correspondingly increases the dynamo voltage.