GB933269A - Improvements in or relating to electro statically screened transformers - Google Patents

Abstract

933,269. Transformers. AUTOMATIC TELEPHONE & ELECTRIC CO. Ltd. April 17, 1961 [May 31, 1960], No. 19198/60. Class 38(2). In a transformer having four coils, each coil being enclosed in an electrostatic screen, the coils are arranged in two similar pairs and secured coaxially, one pair on each face of a rigid insulating board 10 (Fig. 1A) by bonding the coil screen cans to printed circuit tracks 12, 13 thereon. Fig. 2 shows the coils in a transformer assembly wherein the primary and secondary windings are each split in half, a half primary and a half secondary coil each in a separate can being concentrically disposed relatively and forming a group. The primary can parts 18, 22 are soldered together and to the inner printed circuit tracks 12 while the secondary cans are soldered to the outer track 13. There is a gap in each track and a corresponding gap on each associated can to prevent them from acting as short-circuited turns. The can gaps 19, 24 are lapped with insulation tape and then a tape of copper foil to complete the screen. Each screen is then covered with insulating tape to prevent a short circuit between screens. Holes 16, 17 (Fig. 1A) in the boards 10 corresponding with holes in the cans are for the winding interconnections and cutout 15 accommodates the transformer core. The coil assembly -may be vacuum impregnated with wax or insulating compound and after building in the core and connecting the windings the whole assembly may be coated in a varnish. Specification 875,097 is referred to.