Weld free contact system for electromagnetic contactors

摘要

A system and method for preventing contact weld under various fault current conditions is disclosed. The system includes a contactor having stationary and movable contacts biased towards each other and switchable between an open and closed position. Energization of an electromagnetic coil engages the contacts creating an electric path for current flow through the contactor. Pulse width modulation is used to lower the power to the coil and maintain the contacts in the closed position. The contactor is equipped with safeguards to prevent contact welding. Under low fault currents, welding is prevented by contact material composition. Under intermediate fault currents, the contacts are blown open and remain open using magnetic components until the arc dissipates and the contacts have cooled sufficiently. Under high fault currents, the arrangement causes the contacts to blow open and separate the armature from the coil preventing re-engagement of the contacts until the coil is energized again.