Operation; Disk And Bearings; Maintenance - GE IAC51A Instructions Manual

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CONTACT ADJUSTMENT
The contacts should have approximately 1/32
Inch wipe. That
1s
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the stationary contact should be
deflected about
1/~2
Inch when the disk completes
its travel. The contact wipe is adjusted 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 dlal is moved to a position where
the contacts just 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 position of
the arm attached to the shaft which is located below
the time dial. Loosen the screw which clamps the
arm to the shaft and turn the arm, relative to the
shaft, untu the contacts just make at the zero time-
dlal setting.
INSTANTANEOUS UNIT
Select the current above which is desired to
have the Instantaneous unit operate and set the ad-
justable pole piece so that the top of hexagon head
Is
even with the desired calibration on the scale.
To raise or lower the pole piece loosen the locknut
and turn it up or down and then tighten In position.
The contacts should be adjusted 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 contacts and moving
the contacts up or down as required.
A-C TRIPPING UNIT
The a-c tripping unit should not require any
atiention other than occasional cleaning of the con-
tacts. However, if the adjustment should be lost,
it may
be
restored as follows:
Time Overcurrent Relays Type lAC GEH-1753
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 the top of the arma-
ture. The brass backing strip should be adjusted to
allow a 1/16-Inch contact gap with the contacts open.
The compound bushing support should be adjusted to
allow the back of the movable contact to just touch
the brass backing strip when the armature operates
to open the contacts. The outer edge of the com-
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 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 from 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
be
flush against the pole face of both cores, and should
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
being pulled in against the pole face when the lower
coil is energized. Excessive pressure on thearma-
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 screws securely after the proper ad-
justment has been obtained.
OPERATION
Before the relay
Is
put Into service it should be
given a check to determine that factory adjustments
have 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:
DISK 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. 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.
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