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KLF Loss-of-Field Relay
E. Telephone Relay
Apply rated dc volts across terminal 10 and 3. The
telephone relay (X) should open its contact. Manually
close impedance unit (Z) and directional unit (D) con-
tacts and the X contact should close.
8.2 ROUTINE MAINTENANCE
All contacts should be periodically cleaned. A contact
burnisher Style #182A836H01 is recommended for
this purpose. The use of abrasive material for clean-
ing contacts is not recommended, because of the
danger of embedding small particles in the face of
the soft silver and thus impairing the contacts.
8.3 REPAIR CALIBRATION
The relay should be energized for at least one hour.
A. Autotransformer Check
Autotransformers may be checked for turns ratio and
polarity by applying ac voltage to terminals 4 and 5
and following the procedure below.
1)
Set S
and S
on tap number 3. Set the "R"
A
C
leads of M
and M
A
C
"L" leads. Adjust the voltage for 90 volts. Mea-
sure voltage from terminal 5 to the tap #1 of S
It should be 30 volts ( ± 1). From terminal 5 to tap
#2 of S
should be 60 volts. The same procedure
A
should be followed for taps #1 and #2 of S
2)
Set S
and S
on 1 and adjust the voltage at the
A
C
relay terminals for 100 volts. Measure voltage
drop from terminals 5 to each of the M
taps. This voltage should be equal to 100 ( ± 1)
plus the sum of values between R and tap being
measured. Example 100 (1+.03 +.06) = 109
volts.
Transformers that have an output different from
nominal by more than 1.0 volt probably have
been damaged and should be replaced.
B. Impedance Unit (Middle Unit) Calibration
Make the following tap plate settings.
T
= 15.8; T
= 5.1
A
C
S
= S
= 1
A
C
Make M
= M
= -.15 settings:
A
C
"L" lead should be connected to the "0" insert.
"R" lead should be connected to the upper ".06"
insert. (-.03-.06.06 = -.15 between L and R).
all on 0.0 and disconnect the
.
C
and M
A
For the most accurate calibration preheat relay
for at least an hour by energizing terminals 5, 6,
& 7 with 120 volts, 3 phase.
The links in the middle tap block should be set
for the +T
direction (vertical).
C
1)
Contact Gap Adjustment
The spring type pressure clamp holding the sta-
tionary contact in position should not be loos-
ened to make the necessary gap adjustments.
With moving contact in the open position, i.e.,
against right stop on bridge, screw in stationary
contact until both contacts just make (use neon
light for indication). Then screw the stationary
contact away from the moving contact 1-1/3 turn
for a contact gap of .040".
2)
Sensitivity Adjustment
Using the connections of Figure 13, apply 10
volts ac 90° lagging, to terminals 4 and 5 pass
.420 amperes through current circuit (terminals 9
and 8). The spiral spring is to be adjusted such
that the contacts will just close. De-energize the
relay. The moving contact should return to the
open position against the right-hand stop.
.
A
C. Impedance Characteristic Check
1)
Maximum Torque Angle
Adjust resistor R
relay) to measure 8800 ohms. Applying 100 volts
ac to terminals 5 and 4 and passing 5.2
C
amperes, through the current circuit Turn the
phase shifter until the moving contact opens.
Turn the phase shifter back (few degrees) until
contacts close. Note degrees. Continue to turn
the phase shifter until contact closes again. Note
degrees. The maximum torque angle should be
(±3°) computed as follows:
Degrees to Close Contacts at Left +
Degrees to Close Contacts at Right
-------------------------------------------------------------------------------------------------------- -
Adjust resistor R
torque angle is obtained
2)
Impedance Check
a) Adjust voltage to be 90 volts.
For current lagging 90° the impedance unit
should close its contacts at 3.12 – 3.35 amp.
41-748P
(mounted on the back of the
B
2
until the correct maximum-
B
90°
=
17
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