SECTION 7-Breaker Maintenance (Cont.)
FIG.
31 -
2ND UNDERVOLTAGE DEVICE
7.8.2 OPERATIONAL CHECK
When the undervoltage device is used as part of a shut
down circuit which opens the breaker by deenergizing the
coil, the following operational check should be made. It is
recommended that this check be performed every 12 mon
ths or every 17fiJ operations for AKR
30
breakers and
500
operations for AKR fiJ
I
AKRT fiJ breakers.
1. Check the trip latch engagement as described in Sec·
tion 7.15. Trip Latch Adjustment
2.
Check the torque required on the trip shaft to trip the
closed breaker. The value must be 24 inch-ounces max·
imum.
3. Check the response time required to go from zero volts
across
the
undervoltage
coil
to the breaker contacts open
ing. This time should be
20
to
fiJ
milliseconds.
If steps 1 and 2 above are acceptable,
but
the response
time is too high, refer to Section 7
.8.3.
7.8.3 ADJUSTMENTS
It
is recommended that the following checks be made at
the intervals given In Section 7 .8.2.
1 . Hold the armature against the magnet as shown in
Fig.
32A
and check the following:
24
a
The rivet
can tum freely.
b. There is
no
binding between the armature pivot and
the shading ring.
c. There is
a
.CX)1
to .010 inch clearance between
the
rivet and armature as shown In Fig. 32A. This
measurement should be made at the outer edge of
the armature where Its constant radius Is closest to
the rivet.
FIG.
32A -
UNDERVOLTAGE DEVICE
If excessive clearance or binding exists, loosen the
screws holding the magnet assembly to the frame and
move the magnet up or down as necessary. Tighten the
screws to 27 to
32
in-lbs.
2.
The air gap between the armature and magnet with the
undervoltage device de-energized should be
.25
inches.
Check the gap by inserting a .201
±
.005
diameter gage
between the armature and magnet as shown in Fig.
328.
If
necessary reset the air gap adjusting plate so that the gage
pin fits. Tighten the adjusting plate screw to
9
to 1 1 inches
and cover it with RTV
.
3. Check the pick up voltage level with the undervoltage
device mounted on the breaker. Refer to Table
23
for the
allowable voltage ranges. The voltage measurements
should be made at the breaker's secondary disconnects
and with the undervoltage coil energized. The coil should
also be close to room temperature (approx. 20-240C) when
taking voltage measurements. The coil resistance will in
crease as its temperature increases and will change the ac
tual pick up level.
If necessary, the pick up level is changed by using the
adjustment screw shown in Fig. 32A. Remove the locking
wire, tum the screw clockwise to raise the pick up level and
counterclockwise to lower. Once the pick up level is set, In
stall the locking wire. Allow t�-coil to cool and then
recheck the pick up level with 3 quick measurements.
OPEN GAP
ADJUSTMENT
FIG.
328 -
OPEN GAP CHECK
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