GB387921A - Improvements relating to the voltage regulation of alternators - Google Patents

Abstract

387,921. Dynamo-electric machines. ENGLISH ELECTRIC CO., Ltd., 28, Kingsway, London, and ELLEFSEN, O., 18, Redburn Road, Frizinghall, Shipley, Yorkshire. July 8,1932, No. 19356. [Class 35.] Exciting.-A synchronous alternating- current machine has a field winding supplied from a continuouscurrent source independent of the load on the machine and also supplied with rectified current from a half-wave type of rectifier associated with the secondary winding of a transformer, the primary of which is fed by the armature of the machine. In the form shown in Fig. 1, the secondary winding 6 of a current transformer is in series with the field winding 5 supplied from a continuouscurrent source 3a, 3b, and a rectifier 7 of the valve or metal-oxide type is connected across the transformer winding 6. On one set of half-cycles the voltage set up in the winding 6 acts in the same direction as the applied voltage to increase the potential difference across the winding 5, and during the other set of halfcycles, a heavy current circulates in the closed circuit formed by the winding 6 and rectifier 7 without appreciably reducing the potential difference across the winding 5. In a modification, Fig. 2, the field winding is in two parts 5a, 5b connected to slip-rings 9a, 9b, 9c and the rectifier 7 and transformer secondary winding 6 are connected in series across the part 5a which has a lower resistance per turn than the part 5b. If the field winding is to be wound with the same wire throughout, a resistance must be included in the continuous-current circuit ; for this purpose, a resistance element which cannot be cut out may be included in the rheostat 4. In the case of polyphase machines employing a transformer in each phase, the ree ends of the secondary windings are connected together and to the slip-ring 9b, and the free rectifier terminals are connected together and to the slip-ring 9c. The transformer primary winding or windings may be connected across the alternating-current mains 2a, 2b in which case the rectifiers must be reversed if compounding is required so that the rectified impulses oppose the applied exciting voltage.