Time Overcurrent Relays Type lAC
justed to allow a 1/16 -inch contact gap with the con
tacts open. The compound bushing support should
be adjusted to allow the back
of
the movable contact
to just t o u c h the brass b a c k i n g strip when the
armature operates to open the contacts . The outer
edge of the compound bushing should be approxi
mately 1/32 - inch from the inner edge
of
the sta
tionary contact supporting post.
2.
ARMATURE ADIUSTMENT
Loosen the two screws which hold the armature
assembly bracket to the bottom of the frame . Slide
the bracket in or out, whichever is necessary, until
the armature just touches the pole face
of
the upper
core.
In
this position, the armature should be about
1/32 inch f r o m the pole face of the lower core .
Next, slide the bracket in until the armature leaf
spring assumes a vertical position and is spaced
clear of both armature and the vertical tip of the
bracket. With this setting, the armature should
flush against the pole face of both cores, and
put enough pressure on the armature to always re
turn it flush against the pole face of the lower core
after each operation of the unit. This alignment is
important as a slight gap between armature and pole
face of the lower core after the unit operates may
cause contacts to open momentarily, dropping the
relay target when the circuit breaker is reclosed.
Under these conditions, the momentary opening of
the contacts is due to the shock of the armature
be ingpulled in against the pole face when the lower
c o i
1
is energized. Excessive p r e s s u r e on the
armature, caused by the bracket being pushed in too
far, will result in too high a pickup or chattering of
the movable contact during operation of the element.
Tighten the b r a c k e t screws securely a f t e r the
proper adjustment has been obtained.
OPERATION
Before the relay is put into service it should
be given a partial check to determine that factory
adjustments h a v e not been disturbed. The time
dial will be set at zero before the relay leaves the
factory.
It
is necessary to change this setting in
order to open the relay contacts.
The pickup current should be checked on one or
more
of
the taps and the time should be checked for
one or more dial settings.
Recommended test connections for the above
test are shown in Fig.
18.
'
MAINTENANCE
The relays are adjusted at the factory and it is
advisable not to disturb the adjustments.
If,
for any
reason, they have been disturbed, the following points
should be observed in restoring them:
DIS K AND BEARINGS
The lower jewel may be tested for cracks by
exploring its surface with the point
of
a fine needle.
If it is necessary to replace the jewel a new pivot
should
be
screwed into the bottom of the shaft at
the shaft at the same time . A very small drop of
General E lectric meter -jewel oil, or fine watch oil,
should be placed on the new jewel before it is in
serted. The jewel should be turned up until the disk
is centered in the air gaps, after which it should be
locked in this position by the set screw provided for
this purpose .
CONTACT CLEANI N G
For cleaning fine s i
1
v e r contacts, a flexible
burnishing tool should be used. This consists of a
flexible strip of m e t a
1
with
an
etched roughened
surface, resembling in effect a superfine file . The
polishing action is so delicate that no scratches a:fe
/�
left, yet corroded material will be removed rapidly
and thoroughly. The flexibility of the tool insures
the cleaning of the actual points of contact. Some
times
an
ordinary file cannot reach the actual points
of contact because of some obstruction from some
other part of the relay.
Fine silver contacts should not be cleaned with
knives, files, or abrasive paper or
c
I
o t
h.
Knives
or files may leav� scratches which increase arc ing
and deterioration of the contacts. Abrasive paper
or cloth may leave minute particles of insulating
abrasive material in the contacts and thus prevent
closing.
·
The burnishing tool described a b o v e can be
obtained from the factory.
.��""-
PERIO DIC TESTING
An operation test and inspection of the relay at
least once every six months are recommended. Test
connections are shown in Fig. 1 8 .
RENEWAL. PARTS
It
is recommended that sufficient quantities of
renewal p a r t s be carried in stock to enable the
prompt replacement of any that are worn, broken,
or damaged.
When ordering r e n e w a
1
parts, address the
nearest Sales Office of the General Electric Com -
1.4
pany, specify quantity required, name of part wanted,
and give complete nameplate data, including serial
number. If possible, give the G e n e r a
1
Electric
Company requisition number on which the relay was
furnished.
\
For a recommended parts list refer to Part
f
�
Bulletin number CEF2149.
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