TYPES I R P , I RC AND I R D R ELAYS
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 - Tabl e 3 shows the time curve
calibration points for the various type s of rel ays.
With the time di al set to the indicated position, apply
the currents specified by Table 3 ( e . g . for the CD-2,
3 and
20
times tap value current) and measure the
operating time of the relay.
The operating times
should e qual those of Table 3 plus or minus
5
percent.
Indicating Contactor Switches (ICS/1) and ( ICs/T)
A) Clo se 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 l etter "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/1). Thi s value o f current should
not be greater than the particular (ICs/I) tap setting
being used.
The operation indicator target shoul d
drop freely, bringing the letter "I• into view.
C) The contact gap should be approximately
. 047"
between the bridging moving co ntact and the
adjustable stationary contacts. The bridging moving
contact
should touch both
stationary contacts
simultaneously.
Routine M a i n ten a n c e
All relays should be inspected periodically and
the time of op eration should be check ed at least
once every year or at such other time intervals as
may be dictated by experience to be suitable to the
particular 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 periodically cleaned. A
contact burnisher �18 2A836HO 1 is recomm ended for
this purpose. The use of abrasive material for clean
ing contacts is not recommended, because of the
danger of embedding small p article s in the face of
the soft silver and thus impairing the contact.
C al i bration
use the followi ng procedure for calibrating the
relay if the relay has been tak en apart for rep airs or
the adjustments have been disturbed. This procedure
should not be used unl e ss it is apparent that the re
l ay is not in proper working order. ( See .. Acceptance
Check.,).
I n stantaneo u s O vercu rren t U n i t ( 1 )
1 . The upper pin bearing sho ul d 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 securel y locked in position with the
lock nut. The l o wer bearing po sition is fi xed and can
not be adjusted!
2. The contact gap adjustment for the overcurrent
unit i s made with the moving contact in the reset
position , i . e. , against the right side of the bridge.
Move in the l eft-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
.020".
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
pl acing a screwdriver or similar tool into one of the
notche s located on the periphery 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
clo 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 val ue.
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 typ e IRP and IRC relays the directional
unit is the lower cylinder unit. In the type IRD the
directional units are the lo wer and middle cylinder
units.
25
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