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41-973.5R
Relay
PMA, PMA-1
PMD, PMD-1
PM-13 (ac or dc)
PMG-13 (ac or dc)
After momentary application of the transfer-trip volt-
ages as just explained, recheck the calibration of the
monitoring alarm unit (1). If it has changed, make
necessary trimming adjustments of the shunt screws
until there is no change in calibrating of the alarm unit
(1) after the transfer-trip voltage has been applied.
The purpose of this test is to compensate for the
small residual magnetism in the relay unit. The
ground alarm unit (5) will not be affected by this test
as the ampere turns of the two windings cancel each
other.
9.1.7
Alarm Unit (2)
For the alarm unit of the PM-2 or PM-23 relays,
adjust the shunts so that the relay moving contact
floats at one mA dc and closes the left-hand contact
at 0.65 mA dc. The moving contact should float mid-
way between the contact and contact stop at 1.0 mA
dc. There is no high current calibration for this relay
unit.
Now apply 125 volts dc momentarily (one second or
so) across the alarm unit coil-circuit terminals in a
direction to operate the alarm relay. Then recheck
the alarm unit calibration. If there is any change,
touch up the shunt adjustments until there is no
change in calibration after 125 Vdc has been applied.
9.1.8
Tripping Unit (3)
To calibrate the tripping unit of the PM-3, PM-13,
PMG-13, or PM-23 relays, apply a dc voltage as
explained below, to the following relay terminals:
Relays
PM-3
PM-13 (ac or dc)
PMG-13 (ac or dc)
PM-23
Momentarily (one second or so) apply 125 Vdc to the
terminals shown in the chart. Starting with both
shunts all the way in, turn out the right-hand shunt
12
Terminals for Momentary
Application of 125 V dc
POS.
NEG.
6
7
8
9
dc Voltage
Pos.
Neg.
9
8
16
20
8
9
8
9
Type PM Line of Relays For Pilot Wire Monitoring
screw until the relay closes its right-hand trip contact
at 14 volts dc.
NOTE:In the calibration of a PM-23, the alarm unit
(2) contact must be blocked open so as not
to affect the tripping unit pickup. (This will
give approximately 2 mA through the relay
coil.) Now draw out the left-hand shunt
until the relay resets with toggle action
(not gradually) at not less than 10 volts dc.
When the calibration is approximately cor-
rect, again apply 125 volts dc to the indi-
cated terminals, then recheck the pickup
and dropout voltage, making any neces-
sary trimming adjustments of the shunts.
When the relay is properly adjusted, the
application of 125 volts dc will not change
the pickup or dropout voltage points. The
relay should trip and reset with toggle
action in this application. This will require
both shunt screws to be withdrawn farther
than for floating action.
9.1.9
Ground Alarm Unit (5)
For the PM-5 relay, turn both shunt screws all the
way in, then back them out five turns each. Pass a
current of 0.3 mA dc in terminal 6 and out terminal 7.
Following the same general procedure as described
previously in the section entitled "Alarm Unit (1),"
adjust the shunt screws so that the left-hand contact
closes at 0.3 mA. Now pass 0.3 mA dc in terminal 9
and out terminal 8, and adjust for closing of the right-
hand contact at 0.3 mA. Recheck both pickup points
several times, and make trimming adjustments of
both shunts as required to obtain contact closing at
0.3 mA dc in each direction.
For the ground unit (5) of the PMA, PMD, and PMG-
13 relays, connect a variable resistance of about
50,000 ohms in series with a 0-1 dc milliammeter
between the terminals indicated in the following
table:
Relay
L.H. Contact Check
PMA
†
3
and 6
PMD
†
5
and 6
PMG-13
†
3
and 8
†
Milliammeter positive to this terminal
And Transferred Tripping
Relay Terminals
R.H. Contact Check
†
3 and 7
†
5 and 7
†
3 and 9
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