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Introduction - Powerpact B Frame Circuit Breakers Page 10

PowerPact B-Frame 15 to 125 A Circuit Breakers Introduction

Reduced Let-Through Currents

The moving contact has the shape of an elongated S and rotates around a floating axis. The shape of the fixed and moving contacts are such that the repelling forces appear as soon as the circuit reaches approximately 15 times nominal current rating (In). Due to the rotating movement, repulsion is rapid and the device greatly limits short- circuit currents, whatever the interrupting level of the unit. The fault current is extinguished before it can fully develop. Lower let-through currents provide less peak energy, reducing the required bus bar bracing, lowering enclosure pressure, and delivering improved series or combination ratings. For let-through energy values, see PowerPact B-Frame Let-Through Energy Curve, page 78 . For peak let-through current values, see PowerPact B-Frame Peak Let-Through Curve, page 79 .

Internal Operating Mechanism

PowerPact B-frame circuit breakers have an over-center toggle mechanism providing quick-make, quick-break operation. The operating mechanism is also trip-free, which allows tripping even when the circuit breaker handle is held in the ON position. Internal cross-bars provide common opening and closing of all poles with a single ON position. All PowerPact circuit breakers have an integral push-to-trip button in the cover to manually trip the circuit breaker. This should be used as part of a regular preventive maintenance program.

Handle Position Indication

OFF

Trip

ON

OFF position Tripped position ON position

Trip

Res et

4 8 4 8

Trip

Res et

Trip

Res et

4 8

OFF position Tripped position ON position

The circuit breaker handle can assume any of three positions: ON, tripped or OFF. The tripped position provides positive visual indication that the circuit breaker has tripped. The circuit breaker can be reset by first pushing the handle to the extreme OFF position. Power can then be restored to the load by pushing the handle to the ON position.

10 0611CT1603

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