41-748P
KLF Loss-of-Field Relay
16
7.0
INSTALLATION
The relays should be mounted on switchboard pan-
els or their equivalent in a location free from dirt,
moisture, excessive vibration, and heat. Mount the
relay vertically by means of the four mounting holes
on the flange for semi-flush mounting or by means of
the rear mounting stud or studs for projection mount-
ing. Either a mounting stud or the mounting screws
may be utilized for grounding the relay. The electrical
connections may be made directly to the terminals by
means of screw for steel panel mounting or the termi-
nal studs furnished with the relay for thick panel
mounting. The terminal studs may be easily removed
or inserted by locking two nuts on the stud and then
turning the proper nut with a wrench.
For detailed FT Case information refer to I.L. 41-076.
8.0
ADJUSTMENTS AND
MAINTENANCE
The proper adjustments to insure correct operation of
this relay have been made at the factory. Upon
receipt of the relay, no customer adjustments, other
than those covered under “SETTINGS,” should be
required.
8.1 ACCEPTANCE CHECK
The following check is recommended to insure that
the relay is in proper working order. The relay should
be energized for at least one hour.
A. Impedance Unit (Z)
1.
Connect the relay as shown in Figure 13,
page 23, with the switch in position 2 and the
trip circuit deenergized.
2.
Make the following tap settings:
T
A
= 11.5
T
C
=
2.55
S
A
=
2
S
C
=
1
M
A
=-.03 (R/L)
M
C
=
-.09 (R/L)
The reversing links should be set for +T
C
direction (vertical).
This setting corresponds to Z
A
= 23.7 Z
C
= 2.80
Adjust the phase shifter for 90
°
current lagging
the voltage.
3.
With the terminal voltage at 80 volts,
increase current until contacts just close.
This current should be within
±
3% of 2.25
amp (2.32-2.18 amp). This value corre-
sponds to 1.5Z
A
setting since the voltage is
applied to terminals 4 and 5 is equivalent to
1.5 V
IN
voltage, or
4.
Adjust phase shifter for 90
°
current leading
the voltage.
5.
With the terminal voltage at 80 volts increase
current until contacts just close. This current
should be within
±
3% of 19.0 amps (19.6-
18.4 amps) This value corresponds to 1.5Z
C
setting for the same reason as explained
above.
Contact Gap — The gap between the stationary
contact and moving contact with the relay in de-ener-
gized position should be approximately.040”.
B. Directional Unit Circuit (D)
1.
Connect the relay as shown in Figure 13 with
the switch in position 1 and the trip circuit de-
energized.
2.
With a terminal voltage of 1 volt and 5
amperes applied, turn the phase shifter 13
°
(current leads voltage). The contacts should
be closed. This is the maximum torque posi-
tion.
3.
Raise the voltage to 120 volts and vary the
phase shifter to obtain the two angles where
the moving contact just makes with the left
hand contact. These two angles (where
torque reverses) should be where the current
leads the voltage by 283
°
and 103
°
,
±
4
°
volts.
4.
Contact Gap — The gap between the sta-
tionary contact and moving contact with the
relay in the de-energized position should be
approximately.020”.
C. Undervoltage Circuit
1.
Connect the relay as shown in Figure 13 with
switch in position 2 and the trip circuit de-
energized.
2.
Decrease the voltage until the contacts close
to the left. This value should be 80
±
3%
volts.
D. Reactor Check
Apply 120 volts ac across terminal 6 and 7. Measure
voltage from terminal 6 to 4 and 7 to 4. These volt-
ages should be equal to each other within
±
1% volts.
Z
A
V
IN
I
1
----------
80
1.5
--------x
1
2.25
-----------
23.7 ohms
=
=
=
