GB315277A - Improvements relating to electric transformers - Google Patents

Abstract

315,277. British Thomson-Houston Co., Ltd., (Assignees of Wilson M. S.). July 10, 1928, [Convention date]. Transformers. - The ratio error in a current transformer is reduced by subdividing a part of the magnetic circuit into two parallel sections in which unequal flux densities are produced by means of an auxiliary winding embracing one of the sections, the flux densities in the two sections being such that one operates on that part of the permeability curve where permeability increases with flux density while the other section operates on that part of the permeability curve beyond the peak where permeability decreases with increased flux density. Division of the magnetic circuit may be made by perforating the core at one or more points 13. An auxiliary winding 16 in series with the main secondary winding 12 is placed around the smaller sections 15 to increase the flux density therein. Alternatively, increased flux density in the smaller sections 15 may be produced by placing the auxiliary winding on the larger sections 14 in such manner that it opposes the flux in the larger sections. Phase-angle error is reduced by providing a short-circuited winding 20 around one of the core sections.