Patent GB-483784-A (GB)
Title: Improvements in or relating to multi-break electric circuit breakers
IPC: H01H33/14
Filed: 1937-05-27
Abstract: 483,784. High-tension switches arcrupturing in switches. WESTINGHOUSE ELECTRIC & MANUFACTURING CO. May 27, 1937, No. 14720. Convention date, May 29, 1936. [Class 38 (v)] A circuit-breaker comprises a plurality of pairs of separable serially-connected contacts and means for simultaneously opening said pairs of contacts to produce a plurality of serially-connected arcs. Metallic shielding means at least partially surround each pair of contacts and is connected across said pairs of serially-connected contacts, said shielding means being adapted to control the division of voltage between the several pairs of contacts. The Specification points out that, for equal voltage across each of the series-connected breaks, the capacity to earth of the intermediate contacts should be zero and that between the separate breaks should be equal. In Fig. 1 (not shown), is illustrated the mounting of two assemblages such as that shown in Fig. 4 on the lower ends of two lead-in insulators in an oil-tank, together with a bridging contact for co-operating with contacts 49. Each assemblage comprises four arc-quenching units 21 supported by and between a pair of insulating plates 23 secured to a foot member 25 which is threaded on the lead-in conductor. Each unit 21 comprises a fixed contact 27, which is pivoted at 29 and urged downwards by springs 45, and a movable contact 28 which is pivoted to 23 at 37 and at 41 to an insulating rod 39 for simultaneously operating all the breaks. The uppermost contact 27 is connected at 31 to the foot 25 and each movable is connected to the fixed contact below it by lead 43, the lowermost being connected at 51 to contact 49. Each unit 21 has a quenching device 53 comprising a stack of insulating plates 54 which are slotted to provide an aligned passage 56 receiving the contacts. Alternate plates are formed with pockets 57 for retaining are-quenching liquid, and at least three have a U-shaped cut-out part for receiving an iron plate 59, the function of which is to move the arc laterally from the contact tips towards the closed end of the passage 56, thereby volatilizing the liquid in the passage to produce a flow of liquid against the arc. The shielding means is incorporated in the plates 23, and comprise five conducting plates 65..69, suitably spaced and staggered, as shown, the plate 65 being connected at 70 to the foot 25, and plates 66 .. 69 being connected to the respective movable contacts 28 by connections 71 .. 74, respectively. The spacing and amount of overlap is adjusted to produce the necessary potential gradient, and the plates 65 are positioned outermost, so as to be adjacent the tank, so reducing the capacity between the latter and the inner shields 66 .. 69. A similar effect is got from a shield 12 connected with the lead-in conductor. Instead of a pair of plates 23, a cylinder of alternate layers of insulation and metal foil may be employed. In Fig. 7, three units 90 of circular form are provided each with a fixed 95 and movable contact 97 arranged in an annular tubular passage 93 and simultaneously separated by a centrally-arranged rod 105. Each unit 90 comprises upper and lower end plates 99, 98, preferably of magnetic material, having annular recesses for field coils 101, which are connected between their respective end plates and arc horns 102, 103 in the passage 93. When the arc is transferred to horns 102, .103, a radial field is set up by the coils 101 to rotate the arc laterally between the horns in the passage until it is quenched. The units are tied together by rods 110 with suitable spacers 112, the rods being secured to a foot 114 connected to terminal 115. A metal shield 117 is secured to the foot 114, a shield 119 is secured to members 98, 99 of the upper and middle units 90, respectively, and a shield 121 is similarly secured to the middle and lower units. An end bell 127 is secured to foot 114 and a bell-shaped shield 128 is mounted on the lower ends of rods 110, the capacitance between the various shields being connected across the several breaks.