Square D Company

James W Cook

Clark L Oster

Joseph M Khalid

Tery J Evans

Arc suppressor plates in a high amperage molded case circuit breaker are arranged in an arc corresponding to blade travel and define passageways having larger exits aligned with respective vents defined by a molded insulator engaged in the wall of the circuit breaker base.

Vent arrangement for high amperage molded case circuit breaker

Arc control in a high amperage molded case circuit breaker is provided by a steel horn for each of a plurality of contact blades for each phase. The horn has a portion extending into a U-shaped recess in a steel arc runner plate. As the contacts separate, the portion travels close to one wall of the recess and then close to the other wall to transfer the arc from the contacts first to the one wall and then to the other wall which is located adjacent the arc suppressor assembly. A respective adjustment member extending through each horn controls the spacing between the blades and a contact carrier to in turn control the opening sequence of the contacts for minimizing arcing across certain contacts. Arc suppressor plates of alternating length are arranged in an arc corresponding to blade travel and define passageways having their larger exits aligned with respective vents defined by a molded insulator engaged in the wall of the base.

Arrangement for arc transfer in high amperage molded case circuit breaker

A current limiting circuit breaker having for each pole, a pair of main contacts separable upon operation of a thermally and electromagnetically operable tripping device and a pair of auxiliary contacts for current limiting in series with the main contacts and in parallel with a transformable resistor having a positive temperature coefficient of resistance. The auxiliary contacts are separable when an electromagnet is energized by a fault current which simultaneously energizes a field magnet to produce a transverse magnetic field across the auxiliary contacts and the arc formed between them when separating. This simultaneous action of electromagnet and field magnet coacting for rapid contact separation and lengthening of the arc upon flow of a fault current serves to increase arc voltage almost instantaneously to that of the source, about which time the fault current is totally shunted into the resistor. The auxiliary contacts are carried on a pair of minimum inertia movable contact blades to facilitate rapid separation of the auxiliary contacts. The minimum inertia contact blades are elongated between a pivot point and the point at which the contacts are mounted, where they terminate without providing an arc runner portion.

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Solon, IA, United States of America

James W Cook