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torque from being produced in the overcurrent unit.
This arrangement yields a tripping characteristic as
shown in Figure 3.
3.1. OVERCURRENT UNIT
The relays are generally available in the following
overcurrent unit ranges:
RANGE
0.5 - 2.5
0.5
0.6
2 - 6
2
2.5
4 - 12
4
5
These relays may have either single or double circuit
contacts for tripping either one or two circuit break-
ers.
The time vs. current characteristics are shown in Fig-
ures 4 to 8. These characteristics give the contact
closing time for the various time dial settings when
the indicated multiples of tap value current are
applied to the relay
3.2. IIT UNIT
Current ranges available for this unit are: (2 - 48) and
(6 - 144) amperes
3.3. VOLTAGE UNIT
The contacts can be adjusted to close and energize
the slow-release telephone relay over a range of 80
to 100 volts. The contacts open to de-energize the
telephone relay if the voltage is higher than the set
value. The drop-out ratio of the unit is 98% or higher.
Relays are shipped from the factory with a 90 volt
setting.
3.4. 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 instantaneous trip contacts will safely
close 30 amperes at 250 volts dc, and will carry this
current long enough to trip a breaker.
TAPS
0.8 1.0 1.5
2.0
2.5
3
3.5 4
5
6
6
7
8
10
12
3.4.1. Trip Circuit Constants
Indicating Contactor Switch Coil.
Ampere Pickup Ohms dc Resistance
0.2
1.0
2.0
4. SETTINGS OVERCURRENT UNIT (CO)
!
CAUTION
Since the tap block screws carry operating cur-
rent, be sure that the screws are turned tight.
In order to avoid opening current transformer cir-
cuits when changing taps under load, start with
RED handles FIRST and open all switchblades.
Chassis operating shorting switches on the case
will short the secondary of the current trans-
former. Taps may then be changed with the relay
either inside or outside the case. Then reclose all
switchblades making sure the RED handles are
closed LAST.
The overcurrent unit setting can be defined by tap
setting and time dial position or by tap setting and a
specific time of operation at some current multiple of
the tap setting (e.g. 4 tap setting, 2 time dial position
or 4 tap setting, 0.6 seconds at 6 times tap value cur-
rent). The tap setting is the minimum current required
to make the disc move.
To provide selective circuit breaker operation, a mini-
mum coordinating time of 0.3 seconds plus circuit
breaker time is recommended between the relay
being set and the relays with which coordination is to
be effected.
The connector screw on the terminal plate above the
time dial makes connections to various turns on the
operating coil. By placing this screw in the various
terminal plate holes, the relay will respond to multi-
ples of tap value currents in accordance with the var-
ious typical time-current curves.
4.1. INSTANTANEOUS RECLOSING
The factory adjustment of the CO unit contacts
provides a contact follow. Where circuit breaker
41-116.1A
8.5
0.37
0.10
3
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