Patent GB-492486-A (GB)
Title: Electric circuit breaker having arc-extinguishing arrangements
IPC: H01H33/96
Filed: 1937-11-15
Abstract: 492,486. Fluid - blast switches; arc-rupturing in switches. ALLMANNA SVENSKA ELEKTRISKA AKTIEBOLAGET. Nov. 15, 1937, Nos. 31386, 31387, and 31388. Convention dates, Nov. 14, 1936, Jan. 23, 1937, and June 3, 1937. [Class 38 (v)] In an H.T. circuit-breaker in which circuit-interruption is performed by contacts arranged in an extinguishing- pot and closure is performed by contacts in series arranged outside the pot, only one of the contacts is directly connected with the operating mechanism of the breaker, and is so arranged that when closing the breaker it first performs a closing of the contacts in the pot and afterwards, either directly or indirectJy, causes closing of the contacts outside the pot, and when opening the breaker, first causes an opening of the contacts in the pot and then an opening of the contacts outside the pot. In Fig. 1, the movable contact 2 is operated by the operating mechanism and co-operates with contact 13 in an explosion pot 3 which comprises a pair of cylinders 4, 5, and a cover 7, and is secured in a fluid-container 1 by insulating rods or an apertured cylinder 26 to a disc carrying the fixed " make " contact 27. The co-operating contact 15 is fixed to a rod 14 carrying the contact 13, and is housed in a movable cylinder 18 in which works a piston 17. A spring 22 urges the piston 17 downwards and the cylinder 18 upwards so that a collar 21 engages the cover 7. In closing, contact 2 engages 13 and raises rod 14 until 15 engages 27, the fluid in 18 being driven out of holes 23 and between the collar 21 and cover 7. In opening any downward movement of piston 17 creates a partial vacuum above the piston and causes collar 21 to be pressed tightly against the cover 7. The circuit is broken at 2, 13 and the pressure set up by the arc causes the differential piston 8 to descend and force quenching medium upwards through aperture 12. The amount of leakage between 7, 21 is so chosen that spring 22 does not separate the contacts 15, 27 until after interruption of the circuit at 2, 13. Alternatively, cylinder 18 may carry a sleeve contact 13 through which contact 2 passes to engage piston 17. To close the breaker of Fig. 2, a piston 46 carried by contact 35 enters a cylinder 38 to raise the fluid therein so that a piston 43 is lifted from its seating 41 against spring action 47 and raises contact 42 into engagement with contact 45, whereupon piston 43 uncovers holes 40 and contact 45 moves on into contact with 44. When the breaker is opened, the differential piston 48 forces a blast upwards through the apertures in 49 on the separating contact 42 which, when the piston 43 is arrested at 41, is just below the insulating wall 39 and in the most favourable quenching position for the blast from the pot. The differential piston may alternatively be constituted by the movable upper part of the pot, Fig. 3 (not shown). In both these forms, the vents 40 relieve the pressure produced by an are drawn when the contacts 44, 45 make the circuit. In Fig. 4, the extinguishing-pot contact 75 is connected bv a cylinder 76 to a piston 77, which is urged downwards by spring 81 and works in a cylinder 78 communicating with the pot-exterior by channel 80. In opening, contact 79 is held in engagement with contact 84 by the liquid in the space between cylinders 76, 78, retaining the piston 77. An arc is struck between 74, 75, the pressure of which acts on the top of piston 77 to lower contact 79 and draw a second arc in series. When the hole 82 in wall 83 is uncovered by the contact 79, a blast passes upwards to quench the arc between 79, 84, the arc between 74, 75 being quenched by a blast through the aperture 73 in wall 72. This arrangement may be modified by the provision of one or more differential pistons to act on the lower or upper arc, or on both arcs, Figs. 6-7 (not shown). A form in which a differential piston 108 acts on the lower arc is shown in Fig. 8. The breakcontact 101 is fixed to a cylinder 117 which works in a further cylinder 116 on a nave 115 carried by arms 114 from the metal annular part 105 of the pot. Tightening rings 118, 119 are provided for cylinder 117, which is urged downwards by spring 138 and carries a tube 120 on which is the contact 121. The nave 115 and cylinder 116 are separated by a space 126 leading to the pot-exterior through channels 127 in arms 114, the outer ends of some of the channels being provided with seep-holes and of others with ball-valves 128. To close, contact 102 moves cylinder 117 upwards, causing liquid to be sucked into space 126 through valves 128. In opening circuit, an are is drawn between contacts 102, 101, the pressure due to which drives the piston 108 downwards and also acts upon cylinder 117 as a differential piston, tending to assist spring 138 to lower the cylinder 117 and separate contact 121. This movement is, however, retarded by the seep-holes in arms 114 restricting the rate of escape of liquid from space 126. When at length contact 121 frees opening 123 a quenching action occurs additional to that at the piston-wall 110. The larger the current being broken, the faster will cylinder 117 descend, so that the arcenergy is limited to that obtaining with small current.