Patent GB-502694-A (GB)
Title: Improvements in or relating to electric switch gear for alternating current circuits
IPC: H01H33/16
Filed: 1937-09-25
Abstract: 502,694. Oil-break switches. WALKER, C. J. Sept. 25, 1937, No. 26068. [Class 38 (v)] In electric switchgear for polyphase circuits, of the kind comprising contactors each of which is adapted to close two contacts in order to close a circuit, each phase of the total number less one of the phases to be controlled is controlled by gear comprising two switches in parallel, a main or current-carrying switch and an auxiliary or current-rupturing switch, which latter is in series with a resistance. The arrangement is such that when the gear is operated to rupture the current, the first movement opens the main switch so that the current flows through the auxiliary switch and resistance, and further movement opens the auxiliary switch and switches off the current. The switch gears are mounted on common operating means so that they may be operated simultaneously. In the form shown diagrammatically in Fig. 1, the fixed contacts A<1>, B<1> are shunted by circuits comprising, in the case of contacts A<1>, the resistance D<3> and contactor D<2>. The contactors A<2>, B<2> are rigid with the operating rod F, whereas the contactors D<2>, E<2> and that C<3> of the remaining phase are loose on the rod F and operable in the desired sequence by stops F<1>, F<2> and F<3> such that, in opening, first the contactors A<2>, B<2> are. separated from A<1>, B<1> and the current is shunted through D<2>, E<2>, then the latter are opened by their stops F<2>, and finally contactor C<3> is opened. The arcs produced at D<2>, E<2> by the restricted current are quenched by oil-jets from nozzles G', G<2> connected to an oil-pump G operated by the rod F. In the 500 amp. switch of Figs. 2-4, the cover 2 of the oil-tank carries input terminals 3 . . . 5, output terminals 3a ... 5a, and terminals 4b, 5b connected to 4, 5, respectively, over non-inductive resistances 6, 7. The lower ends of 3, 3a are linked at 8, 9 to contacts 10 which are biassed by springs 11, 12 into engagement with fixed contacts 15. which are mounted on a transverse arm 35 of a movable bar 18 by being fitted laterally into a channel-section insulator 39 between side strips 38, 38a of mild steel and copper, respectively. The terminals 4, 5 are each similarly connected to two contacts 13 co-operating with contacts 16, whereas the other terminals are connected to contacts 14, 14a which are located as shown in Fig. 3 and co-operate with contacts i7, 17a respectively. Contacts 16 and 17, 17a are insulatingly carried on transverse arms 36, 37 on bar 18, but, together with contacts 15, are electrically connected to their appropriate arm by copper foil of about 0À001 ohms resistance, as shown at 39 in the case of contact 17a. Bar 18 is carried by rods 19, 20 to which are attached cords 21, 22 secured to pulleys 28, 29 fast on a shaft 30 carrying the operating-handle 32. When the latter is unlatched, the bar 18 falls and contacts 16, due to their shape, disengage their contacts 13 before contacts 17, 17a disengage 14, 14a. The circuit is then from input terminal 4 through resistance 6, terminal 4b, contacts 14a, 17a, arm 36, contacts 17, 14 to output terminal 4a, and similarly for the circuit 5, 5a. Further movement of 18 first separates 17, 17a to open phases 4, 5, and then separates 15 from 10 to open phase 3.