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SECTION 8—Dimensional Checks
With the breaker closed and the gag plate installed, perform
the following dimensional checks.
8.1—Primary Contact Erosion
In the closed position, the erosion disk (item 3, Figure 6)
below the operating rod insulator is aligned with a reference
arm (item11, Figure 6) on new interrupters. As contact
erosion occurs, the erosion disk will move upward from
alignment with that reference arm. When erosion reaches 1/8
®
inch, the PowerVac
interrupters should be replaced. DO NOT
RE-ADJUST THE ALIGNMENT OF THE EROSION INDICATOR
ARM EXCEPT WHEN INSTALLING A NEW VACUUM
INTERRUPTER.
8.2—ML-18 Wipe Spring Compression
With the breaker closed and the closing spring gagged,
measure with a feeler gauge and record the distance
between the top of the wipe indicator and the bottom of the
erosion disk for each phase (see Figure 27, Dimension W).
Trip the breaker with the closing spring gag plate still installed
and measure and record the distance between the wipe
indicator and erosion disk. Subtract the closed position
measurement from the open position measurement. The
result is the amount of wipe on each individual pole. The wipe
is to be greater than 0.075 inch. Adjustment is not required
until wipe is 0.075 inch or less. If adjustment is required see
WIPE ADJUSTMENT in MECHANICAL ADJUSTMENT section.
The ML-18 and ML-18H mechanisms are furnished with very
low gradient wipe springs so that adjustment is not a
precision operation and considerable loss of wipe can be
tolerated without affecting performance.
8.3—ML-18H Wipe Spring Compression
With the breaker closed and the closing spring gagged,
Figure 7 Contact gap
measure with a feeler gauge and record the distance
between the bellville washer and the trunion between the bell
crank arms.
8.4—Contact Gap
The method of measuring the contact gap is as follows: With
the breaker in the open position, the closing springs charged,
and the closing spring gag plate installed, apply a piece of
masking tape to the surface of the operating rod insulator as
shown in Figure 7. Using a reference block, make a mark on
the tape near the top on all three poles. It is also advisable to
put a reference mark on the tape to identify to which pole the
tape is applied. Remove the closing spring gag plate and
close the breaker. Using the same procedure as above, re-
mark the tape. This new mark will be near the bottom of the
tape. Trip the breaker, remove the tapes and re-apply them to
a flat surface. Measure the distance between the two lines.
A caliper will give an accurate reading of the contact gap,
Dimension G: The gaps must be between the 0.60 inch
maximum at the center pole and 0.54 inch minimum at the
outer poles. It is not necessary that all readings correspond. A
properly adjusted breaker will have more gap and wipe on the
center pole than on the outside poles.
8.5—Coil Plunger Gap
The close coil and trip coil plunger gap dimensional checks are
made in the operating mechanism which is accessible from
the bottom. To accommodate these checks, the breaker
should be turned on its right side resting on two-by-four wood
blocks. DO NOT use the portable breaker lift truck.
CAUTION: DO NOT REST UPON OR ALLOW ANYTHING TO
COME
IN
CONTACT
DISCHARGE ROLLER (item 4,Fig. 20) ON THE RIGHT SIDE
OF THE MECHANISM.
1.
2X4 wood blocks
Figure 8 Breaker turned on right side
WITH
THE
CLOSING
SPRING
1
11
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