CONTACT ADJUSTMENT
The contacts should have approximately 1/32
inch wipe. That is the stationary contact should be
deflected about 1/
3
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 dial 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 i'B 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.
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
raiee 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
attention 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-l.nch 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 lcwer 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
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 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 s
ho
ul
d 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
i
s
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.
13
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