GB638861A - Improvements in and relating to electromagnetic induction apparatus - Google Patents

Abstract

638,861. Current transformers. BRITISH THOMSON HOUSTON CO., Ltd. Aug. 10, 1945, No. 20542. Convention date, Aug. 16, 1944. [Class 38 (ii)] Electromagnetic induction apparatus such as a current transformer comprises an annular winding, an annular core which extends through the window of the winding, and a coil wound round a part only of the core so that it is concentrated on the core where it passes through the window of the winding. The annular core is made from flatwise, bent, magnetic strips 6 and completed by a removable yoke 9 at overlapping butt joint areas in the manner described in Specification 621,675. The secondary 7 is wound round the main part 6 of the core and concentrated mainly where it is interlinked by the primary coil (not shown), so that the primary leakage flux which on high loads would saturate the core, is counteracted by the secondary leakage flux so that the ratio correction factor is kept lower and more constant. The yoke 9 is inserted and insulated with material such as crepe paper 14, after secondary 7 and insulation 8 have been wound on part 6 of the core and the primary ring has been placed in its linking position. By omitting some of the strip from yoke 9, a part 20 of the secondary winding may be wound round part only of the core to give partial compensation. Specification 539,730 also is referred to.