Importance

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Abstract

A magnetically operated AC switching device, such as an AC electrical contactor, is operable with a delay-on-dropout feature to permit safe shutdown of equipment energized therethrough in case of power failure. The device includes an AC pickup winding which is energizable from an AC power source and a DC holding winding which is electrically connected to a rectifier for energization of the holding winding with DC power from the AC source. A capacitor is also electrically connected to the rectifier in parallel with the holding winding for energization with DC power from the AC source. Upon energization of the device, the AC pickup winding moves fixed and movable contacts of the device into engagement, and the DC holding winding maintains them in engagement. The AC pickup winding can remain energized without burnout; and upon power dropout the capacitor supplies DC power to the holding winding for an instant to provide a slight delay in the separation of the contacts.

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First Claim