Walter R Lang

US Patent:

42557321, Mar 10, 1981

Filed:

Oct 16, 1978

Appl. No.:

5/951941

Inventors:

John A. Wafer - Beaver PA
Walter V. Bratkowski - McKeesport PA
Walter W. Lang - Rolla MO

Assignee:

Westinghouse Electric Corp. - Pittsburgh PA

International Classification:

H01H 7500
H01H 7700

US Classification:

335 16

Abstract:

A molded case current limiting circuit interrupter includes a pair of pivoting contact arms each supporting a contact and being connected to wiring terminals such that current flows through the contact arms in opposite directions. One of the contact arms has a movable pivot point. A magnetic drive slot motor device is provided to generate electrodynamic contact opening force upon the contact arms during short circuit conditions. A high-speed magnetic trip device releases the operating mechanism under short circuit conditions to move the arm pivot point before the contact arms reclose. A spring latch may be provided to latch the upper contact arm in a contact-separated position during short circuit conditions until such time as the overcurrent flow through the breaker operates a thermal and magnetic trip mechanism to move an operating mechanism to the tripped position. Alternatively, a cam may be provided which is connected by a link to the upper contact arm and positioned such that upon short circuit conditions the contact opening motion of the upper contact arm caused by electrodynamic repulsion forces will cause the connecting link to rotate the cam and move the armature of the magnetic trip device to actuate the trip mechanism and release the operating mechanism to the tripped position, thereby preventing reclosing of the contact arms before the operating mechanism is able to trip. The operating mechanism includes a bracket to allow normal contact reset yet provide a positive closed contact indication if the contacts are welded together.