Specifications

Power-Zone
®
4
General and Application Information
27
11/2005
© 2005 Schneider Electric All Rights Reserved
Two-Step Stored Energy Mechanism
Figure 18: Charging the Closing Springs
Circuit Breaker Inspection
When a Masterpact NW or NT circuit breaker is withdrawn on its rails, the circuit breaker is accessible
for visual inspection. It is easy to remove the arc chutes and visually inspect the contacts and wear
indicator. The operations counter can also indicate when inspections and possible maintenance should
be done.
Figure 19: Masterpact NW Circuit Breaker
Electric motor
charge button
(not shown)
Open/close
indicator
Charging handle
Charged/discharged
indicator
Push to close
button
Operations counter
(optional)
Masterpact NW and NT circuit breakers are
stored energy devices with a two-step
operating mechanism.
Electrically operated circuit breakers have a
motor to charge the stored energy mechanism,
electric close feature, and electric open
feature.
On manually operated circuit breakers, the
closing springs are charged by hand. For
electrically operated circuit breakers, the
springs are charged by an internal electric
motor, but can also be manually charged if no
control power is available.
Status indicators on the front of the circuit
breaker indicate when the closing springs are
charged or discharged.
Push to open
button
Masterpact NW Circuit Breaker on Its Rails
Arc chute
and chamber
Trip unit
Spring
charging
motor
Accessory
terminal
connections
Secondary
disconnecting
contacts
Contact wear
indicator, under
arc chutes *
Operations
counter
Masterpact NW Circuit Breaker Front Plate Removed
* The contact wear indication is available on Micrologic
P and H trip units.
Removable, replaceable, and upgradeable circuit breaker
parts include:
• Arc chutes
• Main disconnecting contacts or clusters
• Internal movable contacts
• Spring charging motor
• Trip unit