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Type PM Line of Relays For Pilot Wire Monitoring
And Transferred Tripping
4.0 CHARACTERISTICS
4.1
NOMINAL CALIBRATION VALUES
Nominal current values to close contacts are listed in
Tables 4 and 5.
4.2
VOLTAGE RATINGS
Supply voltage ratings of the monitoring source
relays to obtain continuous current as follows:
dc
48, 125, and 250 volts
120 volts, 60 hertz (Primary taps 100, 110,
ac
120 and 130)
voltage impressed on the pilot-wire is a nominal 20
volts for monitoring, and 48 volts for tripping. Supply
voltage ratings to obtain remote tripping are: 48, 125,
and 250 volts dc.
4.3
COIL RESISTANCE (EACH WINDING)
Alarm coil (1)
two terminal line
three terminal line
Alarm coil (2)
Trip coil (3)
Ground Alarm coil
4.4
PM-4 AND PM-23 RESISTANCE
Nominal PM-4 and PM-23 total resistance when
adjusted for service is 20,000 ohms less pilot-wire
loop resistance at 1 mA.
4.5
PMA, PMA-1 AND AC PMG-13, PM-13 BUR-
DEN
0.5 VA at tap voltage
1.0 VA at tap voltage
4.6
RECTIFIERS
Approximate forward resistance
Rating
Continuous forward current
amperes
Continuous back
voltage-rms volts
1050-1250 ohms
700-900 ohms
2200-2600 ohms
1800-2200 ohms
5200-5800 ohms
2-terminal line relay
3-terminal line relay
560 ohms at 1 mA
300 ohms at 2 mA
1
200
4.7
REMOTE TRIPPING
Remote trip resistors are listed in Table 2 and 3 for
48, 125, and 250 volts dc.
The relays have sufficient thermal capacity to with-
stand 20 mA dc continuously when remote tripping.
Nominal trip currents in the tripping relays are 5.0 mA
dc with 48, 125, and 250 volts dc supply and a 2000
ohm pilot wire.
4.8
TRIP CIRCUIT
The main contacts will safely close 30 amperes at
250 volts dc and the seal-in contacts of the indicating
contactor switch will safely carry this current long
enough to trip a circuit breaker.
The indicating contactor switch has two taps that pro-
vide a pickup setting of 0.2 or 2 amperes. To change
taps requires connecting the lead located in front of
the tap block to the desired setting by means of a
screw connection.
4.9
TRIP CIRCUIT CONSTANT
Indicating Contactor Switch (ICS)
Tap
0.2 ampere
2.0 ampere
5.0 SETTINGS
Operating units of all relays are adjusted in the fac-
tory to the values listed in Tables 4 and 5 to a toler-
ance of ±8%. No settings are required on these units.
For all 48/125 volt dc relays, connect jumpers across
resistors as shown on the internal schematics.
5.1
PM-4, PM-2, AND PM-23 RELAYS
Adjust the resistors in the PM-4, PM-2, or PM-23 relay
or relays to a value of 1 mA dc with the monitoring cir-
cuits connected for service. Use the milliammeter in the
PM-23 for this purpose or use a portable milliammeter
with a resistance of less than 200 ohms. Where it is not
practical no three-terminal lines to adjust both receiving
relays simultaneously , set one receiving relay for 18,000
ohms total resistance (including relay coil and resistors)
by measurement prior to final adjustment of the other
receiving relay. This procedure will minimize the change
in monitoring current in the first relay to be adjusted
when making the final adjustment of the second relay.
41-973.5R
Resistance
6.5 ohms dc
0.15 ohms dc
5
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