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CONTACT AWUSTMENT
The contacts should have approximately 1/32
3
inch wipe.
That is the stationary contact should be
deflected about 1/
2 inch when the disk completes
its travel.
The contact wipe is adj usted by turning
the screws in the contact brush which regulates the
position of the brush, in relation to the brush stop.
For relays with two circuit-closing contacts, the
tips should be in the same vertical plane.
When the time dial is moved to a position where
the contacts j ust close, the time-dial scale should
indicate zero.
If this is found incorrect, and the
brushes are correctly adjusted, regulate the dial to
read zero.
This is done by changing
the arm attached to the shaft which i'S located below
the time dial.
Loosen the screw which clamps the
arm to the shaft and turn the arm, relative to the
shaft, until the contacts just make at the zero time
dial setting.
INSTAN TANEO US U N I T
Select the current above which i s desired to
have the instantaneous unit operate and set the ad
j ustable pole piece so that the top of hexagon head
is even with the desired calibration on the scale.
and turn it up or down and then tighten in position.
To raiee or lower the pole piece loosen the locknut
The contacts should be adj usted to make at
about the same time and to have approximately 1/8"
wipe.
This adjustment can be made by loosening
the screws holding the stationary c ontacts and moving
the contacts up or down as required.
A -C
TRI P P ING
attention other than occasional cleaning of the con
The a-c
tr ipping unit should not require any
However, if the adj ustment should be lost,
tacts.
it may be re stored as follows:
Before the relay is put into service it should be
given a check to determine that factory adjustments
have not been disturbed.
at zero before the relay leaves the factory.
nec essary to change this setting in order to open the
relay contacts .
The relays are adj usted at the fac tory and it is
advisable not to disturb the adjustments. If, for any
reason, they have been disturbed, the followingpoints
should be observed in restoring them:
DIS K A N D BEARI N G S
The lower jewel may be tested for cracks by
the
position of
I
UN
T
OPERATION
It is
The time -dial will be set
MAINTENANCE
Time Overcurrent Relays Type IAC
1. CONTACT ADJUSTMENT
With the unit de - energized, the movable contact
should lie against the stationary contact with enough
tension to always insure a good closed circuit. The
movable contact brush should be free of any kinks.
Also this contact brush should not touch the com
pound bushing supported from
ture.
The brass backing strip should be adjusted to
allow a 1/1 6 - l.nch contact gap with the contacts open.
The compound bushing support should be adj usted to
allow the back of the movable contact to just touch
the brass backing strip when the armature operates
to open the contacts .
pound bushing should be approximately 1/32 - inch
from the Inner edge of the stationary contact sup
porting post.
2. ARMATURE ADJUSTMENT
Loosen the two screws which hold the armature
assembly bracket to the bottom
the bracket in or out, whichever is necessary, untfl
In this position, the armature should be about
the armature just touches the pole face of the upper
core.
1/32
inch from
the pole face of the lower core.
slide the bracket in until the armature leaf
Next,
clear of both armature and the vertical tip of the
spring assumes a vertical position and is spaced
bracket.
With this setting, the armature should be
flush against the pole face
put enough pressure on the armature to always re
turn it. flush against the pole face of the !ewer 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
Under these conditions, the momentary opening of
relay target when the c ircuit breaker is reclosed.
the contacts
is due to the shock of the armature
being pulled in against the pole face when the lower
coil is energized.
Excessive pressure on the arma
ture, 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 unit. Tighten
the bracket sc rews securely after the proper ad
j ustment has been obtained.
The pickup current should be checked on one or
more of the taps and the time should be checked for
one or more dial s ettings.
Recommended test
test are shown in Fig. 18.
exploring its surface with the point of a fine needle.
If it is necessary to replace the j ewel a new pivot
should be screwed into the bottom of the shaft at
the shaft at the same time.
after which i t should b e locked in this position by
turned up until the disk is centered in the air gap s ,
the set screw provided for this purpose.
GEH - 1 753
the
top of the arma
The outer edge of the com
of
the frame.
Slide
of
both cores, and should
connections
for the above
The j ewel should be
1 3
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