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PowerVac
5kV Vertical Lift
®
Chapter 8. Dimensional Checks
8-1 Primary Contact Erosion
The vacuum interrupter is a sealed unit and the
contacts are not visible. The contacts are de-
signed for 0.125" total wear. When 0.125" of
wear has occured , the vacuum interrupter must
be replaced. Vacuum interrupters are typically
good for 25 full rated interruptions before the
0.125" wear has been reached. Vaccum inter-
rupters are also good for in excess of 10,000
no- load operations and 5,000 load operations.
The mechanical seal system will develop a leak
in the bellows before the contacts will reach
0.125" wear. See Chapter 9 for vacuum integrity
test..
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5
4
1 Operating Rod Insulator
2 Wipe Indicator
3 Wipe Gap
4 Wipe Spring
5 Lock Nut and Lock Washer
6 Coupling Clamps and Screws
7 Hexagon Projection
8 Interrupter Movable Contact Rod
Figure 23. Contact Erosion Indicator
Courtesy of NationalSwitchgear.com
Each interrupter has been premeaseured at the
factory for the primary contact gap and this mea-
surement has been recorded on the ceramic
bottle. This measurement varies from phase to
phase and from breaker to breaker but is ap-
proximately 4 inches. The actual measurement
"A" is the distance from the bottom of the insu-
lated operating rod to the bottom of the lower
stainless steel interruptor support as shown in
Figure 24. To determine contact wear repeat
this measurement on each phase and subtract
the measurement from the factory recorded mea-
surement. If the difference is 0.125" or greater
then the vacuum interruptor should be replaced.
See Chapter 12.
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1
2
3
1
4
5
6
7
1. Lower Interrupter support
2
2. Moving contact rod
3. Coupling clamp
Figure 24. Primary contact erosion
measurment - rear view.
8-2 Spring Wipe Indicator
The wipe springs are preloaded to a length of
2.25 inches When the breaker is closed, the sec-
3
ondary drive cranks will continue to move up-
wards after the primary contacts in the vacuum
interruptor have been closed. This over travel
is taken up by compressing the wipe springs.
The over travel distance is pre-adjusted at the
factory to be 0.125" minimum. The spring wipe
can be verified by viewing the wipe indicator.
(Figure 23, Item 2) The wipe indicator has four
red lines that make up a total distance of 0.125".
The wipe indicator was preset at the factory so
that when the breaker is charged and closed all
four red lines should be visible above the wipe
plate.
26
4. Insulated
operating rod
5. Masking Tape
6. Reference block
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