GB509812A - Improvements in and relating to electric transformers - Google Patents

Abstract

509,812. Transformers. BRITISH THOMSONHOUSTON CO., Ltd. April 12, 1938, No. 11224. Convention date, April 15, 1937. [Class 38 (ii)] In a regulating transformer provided with a main winding 1 which co-operates, through a change-over switch 5, with a regulating coil 2 which can be operated as a series buck or boost connection and is temporarily separated from the main winding during the change over, the regulating coil 2 is provided with a potential surround 6 which is maintained at substantially the potential of the point of the main winding to which the regulating coil is connected. As shown in Fig. 1 the regulating coil 2 is formed as a single layer coil of several conductors arranged as a multiple-helix over a core, the ends of the coil being respectively connected to the contacts 3, 4 of a change-over switch, the movable contact 5 of which is connected to one end of the main winding 1. The potential surround 6 consists of a metal screen which is preferably slit longitudinally and connected by a conductor 7 to one end of the main winding 1. In a modification, part of the main winding is used as a potential surround at both sides of the regulating coil, and the contact arm of the change-over switch is connected to one end of the regulating coil and co-operates with contacts respectively connected to the end of the main winding and to a tapping on the winding, whereby the regulating coil can be connected either in series with the main winding or in parallel with the portion up to the tapping. Fig. 3 shows a further modification, wherein the regulating coil 2 comprises a normally wound tapped cylindrical coil, and the potential surround is formed on one side by a part 8 of the main winding 1 and on the other side by a balancing winding 9 of several parallel connected coils connected to the lower end of the part 8 by a conductor 10. A slit metal cylinder may be used instead of the balancing winding 9.