GB529207A - Improvements in and relating to tap-changing arrangements for windings of alternating current apparatus - Google Patents

Abstract

529,207. Transformers. BRITISH THOMSONHOUSTON CO., Ltd. May 24, 1939, No. 15453. Convention date, May 24, 1938. [Class 38 (ii)] Taps 3 of an auto transformer 2 are brought out to con tacts 4 which are en gageable by a pair o clockwise - rotatable contacts 6, 7 to in crease the outpu voltage. In the posi tion shown, anc when the arm 7 is moving to the nex tap-contact, substan tially all the current flows through the arm 6, since the re sistor 10 is in serie: with arm 7, but when 7 reaches the nex tap-contact, circulating current flows through the resistor. If during this condition, or while the arm 6 is moving over to the next contact, so that arm 7 and resistor 10 are taking all the current, the switching movement is arrested for any reason and there is a danger of the resistor being burnt out, the fuse 9 blows and the switch arm 8 is moved by spring 12 over to contact 11 to insert reactor 13 into the circuit, so avoiding interruption of the supply until the fault is remedied. In Fig. 2, the upper supply lead 1 is connected to the centre tap of a reactor 14 which is normally short-circuited by the switch 8 at contact 15. In the conditions envisaged, however, the switch 8 changes to contact 11, so substituting the reactor 14 for the resistor 10. Since the load current normally divides equally between the two halves of the reactor, it has no injurious arcing effect on normal tap-changing operations. The Specification also shows how apparatus as in Fig. 2 can be added to existing circuits, using centretapped reactors, Fig. 3 (not shown).