CIRCUIT BREAKER
STATIONARY CORE
MOVING CORE
CALIBRATION SCREW
FIG.
13.
Instantaneous Overload Trip
Drop tank and examine the contacts. Remove any
slight burns with a file. Replace contacts when
burns penetrate more than
inch. On the Type
F-11 breaker, burning will be on the top of the moving
contact and on the flared portion of the finger. Con
tacts need be replaced only when burned so badly
as to cause possible stubbing before the next in
spection.
Give the moving contacts a light rubbing with
fine sand paper (not emery cloth). Place the sand
paper over moving contact with the sand side out
and close the breaker three or four times.
Check the insulating quality of the oil. If it tests
below 17 kv in a standard test cup replace it.
When replacing oil be sure to clean out the tank
before refilling. When a portable test set is not
available it is common practice to replace the oil
with new oil and then take the original oil to the
test set, filtering if necessary before re-using. Note
oil need not be replaced just because it is darkened
by suspended carbon. Depend on the test cup test.
Check the tank liners to see that they are not
burned so deeply that there is danger of burning
through before the next inspection.
When replacing the tank be sure it is centered
and draw up all bolts evenly and tightly.
ATTACHMENTS
The instantaneous overload trip shown in Fig.
13
consists of trip coil and trip details to assemble in
the coverplate. The distance between the moving
and stationary cores can be varied as indicated by
the calibration marking for tripping between 5 and
9 amperes in the trip coil. By using current trans
formers of suitable ratio tripping can be accomplish
ed at any desired primary current. In assemblying
be sure that the wedges are put in below the coils.
Also check to see that the trigger is released when
the moving tripping core is raised slowly mechan
ically to within
inch of its total travel. Also check
to see that tripping occurs if moving core is raised
mechanically until trip rod touches trigger and 5
amperes applied suddenly to coil.
The shunt trip attachment for tripping from a
separate source of power as shown in Fig. 14 is
essentially a non adjustable overload trip. Tripping
should occur if moving core is raised slowly the
same as on the overload trip. The coil should pick
up and trip the breaker if 60% voltage is applied.
If moving core is raised to bring trip rod in contact
with trigger, tripping should occur
if
full voltage
is applied to coil. If tripping is actuated by a relay
an auxiliary switch is to be used to interrupt coil
circuit to save relay contacts.
Time delay overload trip as shown in Fig. 15 is
similar to the instantaneous trip with a dash pot
added to the moving core to hold it back. The time
delay can be changed by rotating the partial disk
on the lower end of the trip rod so as to change the
number of the holes uncovered. A loose washer pro
vides for quick resetting. Current calibration is ob
tained by screwing pot into or out of the dashpot
cover.
STATIONARY
CORE
TUBE
MOVING CORE
RIVET
FIG.
14.
Shunt Trip
13
www
. ElectricalPartManuals
. com
