GB750842A - Improvements in and relating to electric circuit interrupters of the liquid blast type - Google Patents

Abstract

750,842. Oil-break switches. GENERAL ELECTRIC CO. Feb. 19,1954 [Feb. 20, 1953], No. 5011/54. Class 38(5) In an arc control device, for an oil-filled circuit-breaker, comprising a casing 4 housing fixed and moving contacts 20, 21 and mounted on a conductor 1, the arc is drawn out, on separation of the contacts, through a stack of insulating baffle plates apertured to form a central arc passage 27 and an offset blast duct 32 communicating by vents with the passage 27. A barrier plate c divides the stack into upper and lower chambers 28, 29, the passage 27 being of smaller diameter in the lower chamber. In the upper chamber, slots in the plates define supplementary, divergent, arc passages 40, 41, Fig. 2, terminating in vents 42 and in the lower chamber similar passages 30, 31, terminating in vents 34 are provided, but of small dimensions. The enlarged parts of the supplementary passages retain the arc within the stack. In operation, a heavy current arc will generate internal pressure in the chamber 28, which is relieved immediately by the vents 42 so that the arc can extinguish itself before the contact 21 has passed the barrier plate c. In the case of medium and low current arcs which generate lower pressures the arc will be drawn down into the lower chamber (if it has-not been extinguished by influx of oil through vents 42 caused by the movement of contact 21), where it will be subjected to a crossblast of oil driven down the duct 32 by the pressure generated in the upper chamber 28, and which will drive the arc into the passages 30, 31 and elongate it about the plate c. To ensure that the arc will be favourably positioned for extinction, arcing tips 23 in alignment with the supplementary arcing passages are provided on the fixed contact. These tips lie in slots 37 in the upper baffle plate. In a modification (Fig. 7, not shown), the bore of the central arc passage is smaller in the upper chamber than the lower one. Specifications 193,136 [Class 38(v)] and 696,161 are referred to.