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6 Operation
W-VACi circuit breakers open and close primary
circuits using Eaton vacuum interrupters (VI). The
device used to open and close the VI is the Universal
Mechanism Assembly (UMA). It is a modular
assembly design. It is a self contained functional unit.
All W-VACi circuit breakers are operated by a front
mounted simple spring charged, stored energy
mechanism (Figure 6-2). The stored energy
mechanism is normally charged by an electric motor,
but also can be charged manually with a charging
handle.
6.1
Encapsulated Pole Units
The VI of the vacuum circuit breaker is incased in an
epoxy resin which is cast by means of Automatic
Pressure Gelation technology. This construction can
effectively protect the vacuum interrupter from external
influences, including external force impact, polluted
environment and so on. The pole unit is mounted on
the back of circuit breaker frame.
6.2
Electrical Circuit
Current flows into poles from one conductor, through
the VI and through an electrical connection, and flows
out the other conductor.
6.3
Operating Mechanism
Keep hands and fingers away from the breaker's
internal parts while the breaker contacts are
closed or the closing springs are charged. The
breaker contacts may open or the closing
springs may discharge causing a serious injury.
Discharge the springs and open the breaker
before performing any breaker inspection or
repair.
The operating mechanism uses stored energy from the
closing spring (Fig. 6-2). The closing unit has one
shunt closing release and the opening unit is
composed of one or more shunt opening release
coil(s). Both have auxiliary switches and indicating
devices which are all installed in the circuit breaker
frame. Closing and opening buttons, the manual
charging handle, spring charging state indicator, and
closed/open indicators are all front accessible.
WARNING
65A7355H01 November 2011 www.eaton.com
Fig. 6-1: Encapsulated Pole Unit (EPU) Structure
1
2
3
4
Fig. 6-2: Universal Mechanism Assembly (UMA)
1. Closing Spring
6. Close Button
2. Charge Indicator
7. Charging Handle
3. Operations Counter
8. Optional Shunt Opening Release Location
4. Auxiliary Switches
9. Open/Close Indicator
5. Motor
10. Open Button
HEAT SINK
TOP
CONDUCTOR
VACUUM
INTERRUPTER
(Internal)
BOTTOM
CONDUCTOR
PUSH ROD
ASSEMBLY
5
6
7
8
9
10
49
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