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57
Recommended Renewal Parts and Replacement Procedures
IB-60201
w. Apply a light coat of Mobilgrease 28
to the left and right sides of the lower
contact block and reassemble the
sliding contact finger assembly. Tighten
with a torque wrench to 8-12 lb-ft. If
present, tighten the set screw in the
bottom of the operating yoke.
x. Tighten the six previously loosened
bolts in the upper contact structure to
45 lb-ft.
y. Fully open the circuit breaker by
reversing
step d
. Reset the opening
springs to the dimension recorded
in step c. Close and open the circuit
breaker about 50 times to properly seat
the vacuum interrupter contact surface.
z. Measure the stroke of the vacuum
interrupter contacts. This can be
accomplished by measuring the
distance from the top of the moving
contact block to the lower flange of
the vacuum interrupter with the circuit
breaker open and again with the circuit
breaker closed. The difference of these
two measurements is the stroke of the
vacuum interrupter contacts. The stroke
for these ratings is 0.35” to 0.4”. If the
stroke is found to be outside of these
limits, it will be necessary to adjust the
operating yoke by turning it upward
or downward. Turning it downward
decreases the stroke, turning it upward
increases the stroke. Each ½ turn of the
operating yoke will change the stroke
by approximately 0.05”.
CAUTION
CAUTION
!
If adjustment of the operating yoke is
required, ensure that the control circuits
are deenergized and the circuit breaker is
deenergized, disconnected by means of a
visible break, and securely grounded. Do NOT
start to work on a closed circuit breaker or a
circuit breaker with the main closing spring
charged.
Operating Yoke Adjustment Procedure:
This adjustment can be accomplished by
the following:
a. If present, loosen the set screw in the
operating yoke.
b. Remove the X-washer from one side of
the pin.
c. While applying a downward force to the
moving contact block just sufficient to
overcome the force of the vacuum, slide
the pin out of the bell crank and the
operating yoke.
CAUTION
CAUTION
!
Do not force the lower contact block down
farther than required to align the pin, bell
cranks, and operating yoke as damage to
the vacuum interrupter bellows and loss of
vacuum may result.
d. Rotate the operating yoke as required.
Turning the yoke downward will
decrease the stroke, while turning the
yoke upward will increase the stroke.
e. Install the pin through the operating
yoke and the bell crank following the
procedure in
step c
. Install the X-washer
and tighten the set screw, if present, in
the operating yoke.
