Instruction Book
Page 44
Effective: February 2007
For more information visit: www.EatonElectrical.com
I.B. 8295A61H07
Figure 7-2 Vacuum Interrupter Showing Contact Erosion
Indicator with Breaker Open (Shown here for Clarity
Purposes Only).
In this case the equipment must be capable of delivering
5 milliamperes for one minute to avoid ambiguity due to
field emission or leakage currents and the test voltage
shall be as shown in Table
7.1.
The current delivery capability of 25 ma ac and 5 ma dc
apply when all three VIs are tested in parallel. If
individual VIs are tested, current capability may be one
third of these values.
WARNING
SOME DC HIGH POTENTIAL UNITS, OPERATING
AS UNFILTERED HALF-WAVE RECTIFIERS, ARE
NOT SUITABLE FOR USE TO TEST VACUUM
INTERRUPTERS BECAUSE THE PEAK VOLTAGE
APPEARING ACROSS THE INTERRUPTERS CAN
BE SUBSTANTIALLY GREATER THAN THE VALUE
READ ON THE METER.
7-5 CONTACT EROSION AND WIPE
Since the contacts are contained inside the interrupter,
they remain clean and require no maintenance. How-
Figure 7-3 Vacuum Interrupter Showing Contact Erosion
Indicator with Breaker Closed (Indicators are Checked
Only When Breaker is Closed).
ever, during high current interruptions there may be a
minimum amount of erosion from the contact surfaces.
Maximum permitted erosion is 1/8 inch. To determine
contact erosion, close the breaker and observe the
vacuum interrupter moving stem from the rear of the
breaker. If the mark on each stem is visible, erosion has
not reached maximum value thus indicating satisfactory
contact surface of the interrupter. If the mark is not
visible, the pole unit assembly must be replaced (Figures
7-2
and
7-3
).
The adequacy of contact wipe can also be determined by
simply observing the indicator on the drive rod toward the
front of the closed breaker. If the wipe is adequate, the
entire vertical portion of the indicator “T” will be visible
along with all or a portion of the horizontal part of the
indicator “T” (Figures
7-4
and
7-5
).
If none of the
horizontal portion shows with the breaker closed, the
wipe is not adequate, and the pole unit assembly must
be replaced.
FAILURE TO REPLACE A POLE UNIT ASSEMBLY
WHEN CONTACT EROSION MARK IS NOT VISIBLE
OR WIPE IS UNSATISFACTORY, WILL CAUSE THE
BREAKER TO FAIL TO INTERRUPT AND THEREBY
CAUSE PROPERTY DAMAGE OR PERSONAL
INJURY.
Summary of Contents for Cutler-Hammer VCP-WR Series
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