Pre-insertion resistor mechanism for a circuit interrupting device

Abstract

A pre-insertion resistor mechanism for a circuit interrupting device of the type which has a pair of normally-engaged contacts. One of the contacts is movable relative to the other contact in an arc-extinguishing environment to selectively separate the contacts to open a gap therebetween to effect circuit interruption. The contacts are continuously, electrically connected to respective, opposed circuit-connectable terminals on the device. The pre-insertion resistor mechanism includes a pre-insertion resistor electrically connected at one end to one of the terminals. The other end of the resistor carries a stationary electrode. A movable electrode assembly which is electrically connected to the other terminal is mechanically coupled to the movable contact so that upon movement thereof to open the gap, the movable electrode simultaneously separates from the stationary electrode. After a predetermined amount of the movement of the electrode has taken place, a latch assembly uncouples the movable electrode assembly from the movable contact permitting the movable electrode assembly to move back toward the stationary electrode. In this way, when the contacts are subsequently re-engaged, the movable electrode assembly leads the main movable contact so that the movable electrode assembly re-engages the stationary electrode prior to the engagement of the contacts. Thus, the circuit is first made between the electrodes, whereat some arcing occurs, with the resistor in parallel with the gap between the main electrodes. When the contacts re-engage, they again carry most of the current through the interrupting device.