MANUALLY SELECTABLE INSTANTANEOUS CURRENT SETTINGS FOR A TRIP UNIT AND ELECTRICAL SWITCHING APPARATUS INCLUDING THE SAME

摘要

A circuit breaker includes separable contacts, an operating mechanism structured to open and close the separable contacts, and a trip mechanism cooperating with the operating mechanism to trip open the contacts. The trip mechanism includes a current transformer structured to sense a current flowing through the contacts and provide a signal representative of the current. A manually operable selector selects one of a plurality of predetermined current conditions by using a plurality of different zener diodes. Each of the predetermined current conditions is greater than an arc reduction maintenance current condition of four times the maximum rated current of the trip mechanism. An instantaneous trip circuit cooperates with the current transformer and the manually operable selector to compare the signal representative of the current with respect to the selected one of the predetermined current conditions. The instantaneous trip circuit responsively causes the operating mechanism to instantaneously trip open the contacts.