Magnum
22
1812.900A
3.4 Operating
mechanism
The Magnum 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 3-10). The
mechanism is a two-step stored energy mechanism.
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 3-11). It takes from
5 to 7 downward strokes on the charging handle to
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
circuit breaker (Figure 3-4).
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. These 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 operated
circuit breaker in the field. Manually operated circuit
breakers are pre-wired to accept this addition.
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 3-10: Electrically Operated Drawout Circuit Breaker with Front Cover Removed
1
3
4
2
5
6
7
8