Electromagnetically operated dc power contactor

Abstract

An electromagnetically operated DC power contactor for high voltage and current use constructed to afford the required contact pressure at the arcing and main contacts with minimal magnet force together with the provision of contact wipe and shearing and rolling action to effect breaking of welds that might occur during contact closure due to bounce at the arcing contacts. A trifurcated movable contact structure is incorporated in this contactor to reduce the current in each of the individual contact segments to approximately 1/3 of the full load current thereby reducing the effective blow-apart force developed at the contacts during fault conditions. Each of the three movable contact segments has both an arcing and main contact at right angles to one another and with similar current carrying capacity, and the three segments together effectively provide a total of three pairs or six current paths to the stationary contact when the contactor is closed to reduce the force required to maintain the contacts in the closed position during a fault condition. The mechanical linkage used to provide the necessary contact motion is constructed to provide maximum mechanical advantage for the device. For this purpose, the position of the pivot of the movable contact assembly is such that maximum contact force develops a force in a downward direction past the armature pivot. This effectively minimizes the torque requirement of the magnet structure since the operating lever arm of the armature and movable contact is reduced considerably as compared to that of the lever arm of a conventional structure.