Patent GB-366998-A (GB)
Title: Improvements relating to electrical circuit breakers
IPC: H01H33/985
Filed: 1930-10-15
Abstract: 366,998. Oil-break switches. BRITISH ELECTRICAL & ALLIED INDUSTRIES RESEARCH ASSOCIATION, WHITNEY, W. B., and WEDMORE, E. B., 36, Kingsway, London. Oct. 15, 1930, Nos. 30920/30 and 20971/31. [Class 38 (v).] Magnetic blow-outs.-A liquid-immersed circuit-breaker has a vent passage or passages for arc-products provided by lateral outlets in the wall of the structure in which the arc is formed, the outlets leading from a point at which arcing commences and being arranged unsymmetrically so that the pressure generated by the arc causes the products to escape in a general direction transverse to the direction of electrode movement. In the form shown in Figs. 1 and 2, a cylinder 1 of gun-metal, surrounded by a casing 5 of "Bakelite" or varnished paper, is located in a tank containing oil, water, or carbon tetrachloride and carries fixed contacts 39 mounted on an extension 37 of the lead-in conductor. An aperture 8 in the wall is lined by an extension of a ring 6 and a frame 9 which is grooved at 10 to receive shelves 11 corresponding to a series of baffle-plates 14 having central apertures 15. Sandwiched between the plates 14 are plates 16 having cut-away parts 17 and lateral outlets 18, and below these are plates 21, the whole being clamped between the ring 6 and an insulating member 22 by means of rings 26, 29. A gland 23 of vulcanized fibre tightly surrounds the movable contact 24 and is adjustable in its seating in the member 22 for alignment purposes. The baffle-plates 14, 16, 21 may be of vulcanized fibre, teak impregnated with oil, or " Sindanyo." Oil from the main body of the container can pass through holes 32 into the space 31 and from there between the window frame 6, 9 and the body 1 to improve the insulation between the latter and hot gases expelled by the arc. When the movable contact 24 is lowered to break the circuit, the arc formed sets up a pressure between the baffle-plates, which pressure causes the are products to be projected across the tip of contact 24 through the outlets 18, thereby extinguishing the arc, the movable contact being finally withdrawn from the container. The window frame, which may be of " Bakelite," has a slightly tapered opening 43, Fig. 3, and may be rectangular, as shown, or conical. Fig. 18 shows a modified form of movable contact, the bore 42 of which is enlarged to receive a flanged tube 47 around which air is trapped so that, when the contact moves down to open the circuit, oil is forced from the bore 42 into the space vacated by the contact. Another way of keeping oil in contact with the arc uses a contact which is slotted on the side opposite the opening 8. On low-voltage circuits, where insulation is not so important, the window frame is dispensed with and the baffles 14, 16 extend through the aperture 8. Fig. 14 shows a form using water as the switch liquid, each break being in a metal pot 76 containing an insulating structure 78 which comprises a single baffle 16 and two lateral outlets. The movable contacts 24 are withdrawn through insulators 80 to break the circuit. The lower part of a unit similar to that of Fig. 1 is modified as in Fig. 15 for interrupting small currents at high voltages. The base 22 below the baffles 14, 16 is formed with a chamber 82 having a baffle to provide two outlets 83, each of smaller area than the main outlets, the chamber 82 and outlets 83 acting similarly to the main chamber and outlets. A stack of plates of oil-soaked teak may be formed with slots and apertures to provide a container. The Specification also refers to other modifications in details, such as the use of a baffle outside the window to avoid stressing the insulators due to escaping gases, the use of magnetic plates in the baffle structure, and the venting of the gases alternately to one side and the other from the shallow chambers. Numerical data as to sizes of parts and rupturing capacity are also given.