Current Balance Relays
Types
UC
ADJUSTMENTS
TARGET
AND
SEAL-IN ELEMENT
For trip coils operating on currents ranging
from 0.2 up
to
2.0 amperes at the minimum control
voltage, set the target and seal-in tap plug in the
0.2-ampere tap.
For
coils operating on currents ranging
from 2 to
amperes at the minimum control volt
a e, place the tap plug in the 2-ampere tap.
The tap plug is the screw holding the right-hand
stationary contact of the seal-in element. To change
the tap setting, first remove the connecting plug.
Then, take a screw from the left-hand stationary
contact and place it in the desired tap. Next remove
the screw from the other tap, and place it in the
left-hand contact. This procedure is necessary to
prevent the right-hand stationary contact from
ting out of adjustment. Screws should not be in
taps at the same time as pickup for d-e will be the
higher tap value and a-c pickup will be increased.
PICK-UP SETTING
Pick-up of the relay is adjusted before it leaves
the factory. Pick-up, current required to close the
contacts with zero restraint, can be adjusted b y
turning the cor.trol spring adjusting ring. This ring
has slots the proper size to fit most screw driver
blades.
inserting the blade of a screw driver
into one
the slots, the ring can be turned.
If
the
ring is turned in the contact opening direction, the
pick-up will be raised.
If
the ring is turned in the
contact closing direction, the pick-up will be low
ered.
TIME SETTING
For a
condition, time may be adjusted in
two ways.
time lever setting controls the con
tact travel, hence the time. The drag magnet may
be moved on its shelf away from the disk shaft for
increased time and toward the disk shaft for de
creased time. The time lever gives the greater
range of adjustment and is more convenient.
To set the time of a particular unit it is nec
essary to impose the desired conditions on the unit
and measure the time required to close the contacts
with a standard timer, Adjust the time lever and
drag magnet until the desired time is obtained.
OPERATION
Before leaving t h e factory, the relays were
tested and adjusted for correct operation. The only
adjustment which should be necessary is setting the
time lever, and i f necessary, adjusting the drag
magnet, for the correct time.
It
may be that the control spring will not reset
the contacts all the way back to the time lever. This
condition will cause no difficulty, however, because
a s soon as the relay is energized with balanced
currents of applicable magnitude the torque of the
restraint U-magnet will reset t h e contacts. As
noted before, the chief function of the spring is to
open the contacts when the relay is de-energized.
MAINTENANCE
The relays are adjusted at the factory and it is
advisable not to disturb the adjustments.
If
for any
reason,
have been disturbed, the following
points
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 same time. A very small drop of General Elec
tric meter-jewel oil, or fine watch oil, should be
placed on the new jewel before it is inserted. The
jewel should be turned up until the disk is centered
in
the air gaps, after which it should be locked in
this position b y the set screw provided for this
purpose.
CONTACT CLEANING
F o r cleaning fine silver contacts, a flexible
burnishing tool should be used. This consists of a
flexible strip o f metal with an etched roughened
surface, resembling in effect a superfine file. The e
polishing action is so delicate that no scratches are
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 cloth. Knives
or files may leave scratches which increase arcing
and deterioration of the contacts. Abrasive
or cloth may leave minute particles of
abrasive material in the contacts and thus prevent
closing.
The
tool described above c a n be
obtained from the
CONTACT ADJUSTMENTS
With the contacts open the stationary contact
should be engaged with the adjustin screw and should
deflect about 1/32" before it is stopped by the back
stop.
7
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