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56
Maintenance
01.4IB.77020
PowlVac-ND
®
and PowlVac-NDA
™
Series 4
Vacuum Circuit Breakers
6) Electrical Operation
After performing any necessary mechanical
and lubrication maintenance, operate the
circuit breaker electrically several times to
ensure that the electrical control system
works properly. See
D. Placing the Circuit Breaker Into Service,
.
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1) Vacuum Interrupter and Contact Erosion
The contact travel of the vacuum
interrupter contacts is measured by
subtracting the lengths between the lower
contact block and the vacuum interrupter
linkage pins in both the open and closed
positions.
Using calipers, measure from the bottom of
the lower Current Transfer Block to the top
of the Operating Pin. Refer to
. Record the value measured.
Figure 22 Measurement of Open Position
a
b
c
a. Open Position Gap
b. Bottom of Current Transfer Block
c. Top of Operating Pin
Measure the distance between the bottom
of the lower Current Transfer Block and the
top of the Operating Pin.
Figure 23 Measurement of Closed Position
a
b
c
a. Closed Position Gap
b. Bottom of Current Transfer Block
c. Top of Operating Pin
Then, subtract the Closed Position from the
Open Position. This value is the Contact
Wipe. Record and date this value in the
Maintenance Log. It is the starting point for
monitoring contact wear.