GB618709A - Improvements in and relating to dynamo electric machines - Google Patents

Abstract

618,709. Exciting dynamo-electric machines. HILL, E. P., and METROPOLITAN. VICKERS ELECTRICAL CO., Ltd. Nov. 13, 1946, No. 33711. [Class 35] In a generator whose output voltage is required to vary in linear relationship with the current in a controlling field winding, the drooping effect of the saturation of the generator field is offset by boosting with a shunt field winding connected through a non-linear resistance. This resistance is composed of material known under the Registered Trade Mark " Metrosil," which allows a disproportionate current to flow in the shunt field winding for high voltages. In the form shown in Fig. 1, the separately excited field winding 2 of a generator 1 is boosted by a shunt field winding 3 connected in series with a non-linear resistance 4. In another form (Fig. 4) the shunt field winding 3 and controlling winding 2 act on an exciter 5 which in turn energizes the main generator 1. This exciter which may be a metadyne or armature-reaction type of machine, may have several controlling windings so that the generator output is governed by a combination of factors. An arrangement is shown in which the shunt winding is used to limit the generator output or other quantity, by means of a relay which reverses its polarity so that it bucks the separately excited winding at a predetermined value of armature current. In a further modification, the response of the generator to the controlling field is quickened by connecting this field winding in series with the secondary of a transformer whose primary carries the generator armature current. Specification 574,155 is referred to.