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41-116K
150
100
50
0
higher than the set value. The dropout 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.
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.
3.4.1. Trip Circuit Constants
Indicating Contactor Switch –
0.2 amp tap 6.5 ohms dc resistance
2.0 amp tap 0.15 ohms dc resistance
4.0 SETTINGS
!
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-
4
The Trip Area May be Changed As Follows:
The line "bc" may be moved in the direction of arrow "y" by changing
the voltage unit setting. The line "ab" may be moved in the direction
of arrow "x" by changing the CO unit tap setting. Tap value current
expressed in% Full Load defines line ab, and voltage unit setting
expressed in% Normal Voltage defines line bc.
b
X
0
50
a 100
CURRENT IN PERCENT OF FULL LOAD
Figure 3: Typical Tripping Characteristics of Type COV Relay
Y
TRIP AREA
150
200
250
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.
4.1
OVERCURRENT UNIT (CO)
The overcurrent unit settings can be defined either by
tap settings and time dial position or by tap setting
and a specific time of operation at some current mul-
tiple 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 current).
To provide selective circuit breaker operation, a mini-
mum coordinating time of 0.3 seconds plus 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.
4.1.1. Instantaneous Reclosing
The factory adjustment of the CO unit contacts pro-
vides a contact follow. Where circuit breaker reclos-
ing will be initiated immediately after a trip by the CO
contact, the time of the opening of the contacts
should be a minimum. This condition is obtained by
loosening the stationary contact mounting screw,
removing the contact plate and then replacing the
plate with the bent end resting against the contact
spring.
Type COV Voltage
Controlled Overcurrent Relay
c
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