TYPES I R P , I RC AND I RD R E L AYS
blocked closed, alternately apply tap value current
plus 3% and tap value current minus 3%. The moving
contact should leave the backstop at tap value current
plus 3% and should return to the backstop at tap value
current minus 3%.
3. Time Curve - Table 3 shows the time curve
calibration points for the various types of relays.
With the time dial set to the indicated position, apply
the currents specified by Table 3 (e.g. for the co-2,
3 and 20 time s tap value current) and measure the
operating time of the relay.
The operating times
should equal tho se of Table 3 plus or minus 5 percent.
Indicating Contactor Switches (ICS/1) and (ICS/T)
A) Close the contacts of the CO and pass suf
ficient d.c. current through the trip circuit to close
the contacts of. (ICS/T) . This value of current should
not be greater than the p articular (ICS/T) tap setting
being used. The operation indicator target should
drop freely, bringing the letter "T" into view.
B) Close the contacts of the instantaneous over
current unit (I) and the directional unit (D). Pass suf
ficient d. c. current through the trip circuit to close
the contacts of (ICS/I). This value of current should
not be greater than the p articular (ICS/1) tap setting
being used.
The operation indicator target should
drop freely, bringing the letter "I" into view.
C) The contact gap should be approximately
. 04711
between the bridging moving contact and the
adjustable stationary contacts. The bridging moving
contact should touch both stationary contacts
simultaneously.
R o u t i n e M a i n ten a n c e
All
relays should be inspected periodically and
the time of operation should be checked at least
once every year or at such other time interval s as
may be dictated by experience to be suitable to the
oarticular application. The use of phantom loads, in
testing induction-type relays, should be avoided,
since the resulting distorted current wave form will
produce an error in timing.
All contacts should be p eriodically cleaned. A
contact burnisher t�l82A8 36HO 1 is recommended for
this purpose. The use of abrasive material for clean
ing contacts is not recommended, because of the
danger of embedding small p articles in the face of
the soft silver and thus impairing the contact.
C al i bration
Use the following procedure for calibrating the
relay if the relay has been taken apart for repairs or
the adjustments have been disturbed. This procedure
should not be used unless it is apparent that the re
l ay is not in proper working order. ( See "Acceptance
Check .,).
I n stantaneo u s O v e rcu rren t U n i t ( 1 )
1 . The upper pin bearing should be screwed down
until there is approximately .025 cl earance between
it and the top of shaft bearing. The upper pin bearing
shoul d then be securely locked in po sition with the
lock nut. The lower bearing po sition is fixed and can
not be adjusted!
2. The contact gap adjustment for the overcurrent
unit is made with the moving contact in the reset
position , i.e. , against the right side of the bridge.
Move in the left-hand stationary contact until it just
touches the moving contact then back off the station
ary contact 2/3 of one tum for a gap of approximately
. 0 20 " .
The clamp holding the stationary contact hous
ing need not be loosened for the adjustment since the
clamp utilizes a spring-type action in holding the sta·
tionary contact in position.
3. The sensitivity adjustment is made by varying
the tension of the spiral spring attached to the mov
ing element assembly.
The spring is adjusted by
placing a screwdriver or similar tool into one of the
notche s located on the p eriphery of the spring ad
juster and rotating it. The spring adjuster is located
on the underside of the bridge and is held in place
by a spring typ e clamp that doe s not have to be
loo sened prior to making the necessary adjustments.
Before applying current, block open the normally
do sed contact of the directional unit. Insert the tap
screw in the minimum value tap setting and adjust
the spring such that the contacts will close as indi
cated by a neon lamp in the contact circuit when
energized with the required current. The pick up of
the overcurrent unit with the tap screw in any other
tap should be within
±
5% of tap value.
If adjustment of pick-up current in between tap
settings is desired insert the tap screw in the next
lowest tap setting and adjust the spring as described.
It should be noted that this adjustment results in a
slightly different time characteristic curve and burden.
Directional Unit (D)
In the type IRP and IRC relays the directional
unit is the lower cylinder unit. In the type IRD the
directional units are the lower and middle cylinder
units.
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