3-3.2 Primary Stationary Contacts; Operating Mechanism; 3-4.1 Manual Operation - Eaton MDN-408 Instructions For Installation, Operation And Maintenance

3-3.2 PRIMARY STATIONARY CONTACTS

The primary stationary contact is a combination of two
items (Figure 3-10). One is a conductive pad mounted
on the line conductor which functions as the stationary
main contact. The other is an arc runner, also connect-
ed to the line conductor. The integral arc runner serves
a dual purpose:
• Fixed arcing contact
• Part of the arc chute

3-4 OPERATING MECHANISM

The Magnum DS/DSX/DSL operating mechanism is
based on the proven cam and spring design of the DSII
power circuit breaker. It is easily accessed by removing
four cover screws and the front cover (Figure 3-11).
The mechanism is a two-step stored energy mecha-
nism. Potential energy is stored to close the circuit
breaker. Sufficient energy to open the circuit breaker
remains available after a closing operation.

3-4.1 MANUAL OPERATION

On manually operated circuit breakers, the closing spring
can only be charged manually. To manually charge the
spring, insert one finger in the recess behind the charging
handle and pull out. This permits a gloved hand to grasp
the handle and begin charging (Figure 3-12). It takes
from 5 to 7 downward strokes on the charging handle to
1 Secondary Wiring Points
2
Field Installable Accessories
(3 maximum)
3 Trip Unit
4 Electric Charging Motor
5
Manual Charge Handle
6 Operations Counter (optional)
7 Padlockable Levering Device
Access Door
8 Breaker Position Indicator
Figure 3-11 Typical Electrically Operated Drawout MDS/MDSX Circuit Breaker with Front Cover Removed
I .B. 2C12060H08
complete the manual charging process. It is possible to
manually recharge the spring immediately after closing
the circuit breaker and before it has been tripped open.
Standard manually operated circuit breakers are closed
and opened by hand using the Manual "ON" and Manual
"OFF" buttons respectively located on the front of the cir-
cuit breaker (Figure 3-5). Performing either operation is
accomplished by pressing and releasing the appropriate
button. Access to these pushbuttons can be limited by
the use of an optional, padlockable cover. In addition,
complete access to the "ON" button can be prevented
with an optional prevent close cover. The status of the
springs and the primary contacts are always indicated in
an indicator window just above the pushbuttons.
Electrically operated optional devices are available to
automatically close or trip a manually operated circuit
breaker. An electrical spring release is available to close
a manually operated circuit breaker. Two optional
devices, a shunt trip and an undervoltage release, are
available to automatically trip (open) a manually operated
circuit breaker. All of these UL listed optional devices can
be installed easily in the field. For more details on these
devices, refer to paragraph 3-8 in this manual.
An electrical operator which is used to charge the closing
spring automatically can be added to a manually operat-
ed circuit breaker in the field (Figure 3-13). Manually
operated circuit breakers are pre-wired to accept this
addition.
For more information visit: www.EatonElectrical.com
Instruction Book
Effective: May 2006
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