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41-151.1H
Figure 5: External Schematic Diagram for Use of External
Auxiliary Relay to Prevent Pumping of the Type D-
3 Relay when used for Overload Protection.
mately 5 seconds when a shunt is used, and 2 sec-
onds when there is no shunt.
Continuous maximum overload is approximately
1500% of full scale.
The minimum setting which D-3 Relay can accom-
modate is 5% of the full scale.
5.0 SETTINGS
For reverse-current protection a sensitivity of 2 per
cent is obtained when using a standard 50 milli-volt
shunt and setting the relay at 1 millivolt. A 10 per
cent sensitivity is obtained by setting the relay at 5
millivolts. These values of sensitivity can be doubled
by using a 100 millivolt shunt.
For overload protection the relay is set at the index
setting which, with respect to the millivolt drop of the
shunt, will operate at desired per cent of overload.
4
183A344
Figure 6: Internal Schematic of the Type D-3 Relay in the
Type FT-21 Case with Self-Contained Auxiliary
Relay used to Prevent Pumping on Overload Pro-
tection.
5.1
TRIP CIRCUIT
Contacts
D-3 relay
contactor switch
(when supplied)
6.0 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
Type D-3 Direct Current Relay
Amperes contacts will:
(non-inductive load)
dc control
voltage
open
close
125 V
0.04
1.0
250 V
0.02
1.0
125 V
3.5
3.0
250 V
1.0
3.0
182A785
carry
continuously
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5.0
5.0
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