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41-347.12C
I
= 2.36 to 2.56 times tap value current.
LR
Indicating Contactor Switch (ICS)
Initially adjust unit on the pedestal so that armature
fingers do not touch the yoke in the reset position.
(Viewed from top of switch between cover and
frame.) This can be done by loosening the mounting
screw in the molded pedestal and moving the ICS in
the downward position.
1. Contact Wipe - Adjust the stationary contact so
that both stationary contacts make the moving
contacts simultaneously and wipe 1/64" to 3/64"
when the armature is against the core.
2. Target - Manually raise the moving contacts and
check to see that the target drops at the same
time as the contacts make or up to 1/16" ahead.
The cover may be removed and the tab holding
the target reformed slightly if necessary. How-
ever, care should be exercised so that the target
will not drop with a slight jar.
3. Pickup - The unit should pickup at 98% of rating
and not pickup at 85% of rating. If necessary, the
cover leaf springs may be adjusted. To lower the
pickup current use a tweezer or similar tool and
squeeze each leaf spring approximate equal by
applying the tweezer between the leaf spring and
the front surface of the cover at the bottom of the
lower window. If the pickup is low, the front cover
must be removed and the leaf spring bent out-
ward equally.
Calibration (35%-Sensitivity Relays)
The differential unit (DU) should first be calibrated as
outlined under "Calibration (All relays)". Next the
right-hand shunt of the lower polar unit should be
turned out until the relay separates at:
I
= .45 times tap value current
ac
I
= 1.64 times tap value current
LR
This changes the percentage slope curve of the relay
to that shown by the 35 percent sensitivity curve of
figure 7. Pickup of the relay is increased from 30% to
approximately 35% of tap value current and the
curve is changed at low values of restraint current to
that shown in figure 7. At large values of restraint cur-
rent the percentage slope characteristic is essentially
the same as shown in figure 8.
20
As shown in figure 7, the margin of safety between
the relay calibrated for a 35% sensitivity and the 20%
mismatch curve is the same as that of the relay cali-
brated for a 30% sensitivity and the 15% mismatch
curve. This margin of safety is also shown in the volt-
age differential characteristic of figure 11 for the 35%
sensitivity relay.
Electrical Checkpoints
The following electrical checkpoints may be used to
assist in troubleshooting if the relay will not calibrate
using the above calibration procedure. The values
listed are approximate for current production and
might change due to a minor change in design or a
change in components. However, periodic checks of
a given relay should reproduce very closely the same
values produced when the relay was new.
Differential Unit (DU)
A. Restraint Circuit
Apply two times tap-value current successively
to each restraint transformer. This is done by
connecting leads to a tap screw and to terminals
5, 7, 9 (HU-1 only) in turn. The ac voltage across
the appropriate restraint rectifier bridge using a
high resistance voltmeter (5000 ohms per volt)
should be within the range given in Table 3.
Table 3:
Rated Frequency
DU Restraint Circuit
DU Operating Circuit
Operate Coil Bridge
Operate Transformer
HRU
1. Output of operate
transformer (top coil
terminals)
2. 4 MFD capacitor
(HRU Restraint)
3. .45 MFD capacitor
(HRU Operate)
Rectifier Bridges
4. Operating
5. Restraint
6. Series-Filter
Reactor
Location of the appropriate bridges is shown in
figure 18.
Voltage Range
50 Hz
60 Hz
1.78 – 2.03
2.10 – 2.40
2.17 – 2.69
2.50 – 3.10
2.97 – 4.05
4.40 – 6.00
3.98 – 4.89
3.90 – 4.80
2.41 – 3.33
2.27 – 3.13
2.89 – 3.97
3.30 – 4.40
1.87 – 2.88
1.95 – 3.00
<1.2
<1.0
<1.0
<0.5
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