CIRCUIT INTERRUPTER WITH ELECTROMAGNETIC OPENING MEANS

摘要

1490262 Electrodynamic protective switches WESTINGHOUSE ELECTRIC CORP 13 Jan 1975 [29 Jan 1974] 1274/75 Heading H1N A circuit interrupter has a magnetic slot motor comprising a structure of laminated magnetic material 59 having a slot 63 in which a movable contact carrier 27 can move up and down rectilinearly out of and into contact respectively with fixed contacts 33, and a magnetic holding device comprising a holding magnet 43 and a keeper 53. The arrangement is such that when the contacts are closed under normal working conditions the keeper cooperates with the magnet to hold the contacts closed against a separating force produced by the reaction between the current in the movable contact carrier and the current in the structure of laminated magnetic material, but under excess current conditions a threshold force is exceeded and the holding force between the magnet and the keeper is overcome and the contact carrier moves in the slot to open the contacts. A nylon pad 69 is used in the slot to buffer the movable contact carrier. The contacts are reclosed by insertion of a tool through an aperture 57 in the housing of the circuit interrupter to depress the keeper 53 into contact with the holding magnet 43 again. In a further embodiment, Fig. 4, not shown, there is an additional contact opening arrangement responsive to lower fault currents wherein the flux of the holding magnet is opposed by flux generated, when such fault currents flow, in a coil associated with the magnet to weaken the field of the holding magnet and allow the keeper to be moved away from it under the influence of a bias spring which also then opens the contacts. The coil associated with the magnet is excited under the control of a bimetallic strip, or manually. Alternatively the keeper can be released from the holding magnet by shunting some of the field of the magnet by a manually operated magnetic shunt. In this embodiment a further movable keeper is interposed between the first keeper and the holding magnet to enable the magnetic holding device to be reset before reclosure of the contacts.