GB952417A - Combined transformer and variable choke - Google Patents

Abstract

952,417. Transformers. HIRST ELECTRONIC Ltd. Feb. 1, 1963 [Feb. 1, 1962; Feb. 27, 1962; Nov. 1, 1962], Nos. 3921/62, 7669/62 and 41407/62. Heading H1T. A transformer core forms with a further movable iron core element the magnetic circuit for a choke coil which is connected in series with the transformer secondary and surrounds a limb of the movable core but is fixed relative to the transformer. The choke core 17 (Fig. 1) which moves in guides (not shown) to prevent movement in a direction parallel to its yoke, has its limbs aligned with those of the transformer and these may number two, three (Fig. 1) or more the mating surfaces being in the form of notches 25 and projections 26 which reduce the high rate of change of choke reluctance after initial separation of the cores, by decreasing the effective air gap length. For three-phase applications, each of three transformer limbs may carry a primary 12 and a secondary 13 and the corresponding choke limb may carry one winding 18 which can be tapered or stepped and may be located by castellations 19. A singlephase winding may be formed on one limb as above, or may be distributed on a two-limb core (Fig. 3, not shown). The arrangement can provide an output range of 5-375 amps., as compared with 5-100 amps. if choke coils are fixed to the choke core. The first Provisional Specification describes welding rectifier applications in which a fan is used to cool the transformer assembly.