T r i p C i rc u i t Con stants
Indicating Contactor Switch -
0 . 2 ampere tap - 6.5 ohms d-e resistance
2 . 0 ampere tap - 0. 15 ohms d-e resistance
Au xi
I
i ary Switch ( C S- 1 )
The auxiliary switch has a d-e resistance of
1 1 65 ohms .
Type I R P R e l a y
The IRP relay i s designed for potential polariza
tion and has its maximum torque when the current
lags the voltage by approximately 60 degrees. The
shifting of the maximum torque angle is accomplished
by the use of an internally mounted phase shifter as
shown in the internal schematic.
The directional unit minimum pick-up is approxi
mately 1 volt and 2 amperes at its maximum torque
angle for the directional units used with the 0 . 5
t o 2.5 and 2 t o 6 ampere range time over-current units.
For the directional units used with the 4- 12 ampere
range time overcurrent units the minimum pick-up is
1 volt and 4 amperes .
Type I R C R e l ay
The IRC relay is designed for current polariza
tion and has its maximum torque when the operating
current leads the polarizing current by approximately
40° .
The directional unit minimum pick-up is 0 . 5
ampere in each winding at the maximum torque angle
for the directional units used with the 0 . 5 to 2.5 and
2 to 6 ampere range time overcurrent units. For the
directional units used with the 4-1 2 ampere range
time overcurrent units the minimum pickup is 1
ampere .
T y p e I R D R e l ay
The type IRD relay utilizes a directional unit
similar to the IRC relay in conjunction with the direc
tional unit and phase-shifting circuit of the IRP relay.
The current-polarized directional unit of the IRD
relay operates on residual currents while the poten
tial-polarized directional unit of the IRD relay oper
ates on residual voltage and residual current.
For the directional units used with the 0.5 to 2
and 2 to 6 ampere time overcurrent units, the mini
mum pick-up of the current polarized unit is 0. 5
ampere in each winding at the maximum torque angle.
The minimum pick-up for the voltage polarized unit is
20
1 volt and 2 amperes with the current lagging voltage
by 60° .
For the directional units used with the 4 to 12
ampere range time overcurrent units, the minimum
pick-up is 1 ampere for the current-polarized dtrec
tional unit and
1
volt and 4 amperes for the voltage
polarized directional unit.
S E T T I N G S
T i m e O ve rcu rrent U n i t ( CO)
The time overcurrent unit settings can be defined
either by tap setting. and time dial po sition or by tap
setting and a specific time of operation at some cur
rent 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 current).
To provide selective circuit breaker operation, a
minimum 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 screws on the tap plate above the
time dial makes connections to various turns on the
operating coil. By placing this screw in the various
tap plate holes, the relay will just close its contacts
at the corresponding current 4-5-6-7- 8- 1Q-1 2 amperes,
or
as
marked on the tap plate.
C AU T I O N
Since the tap block connector screw car
ries operating current, be sure that the screw is turned
tight.
In order to avoid opening the current trans
former circuits when changing tap s under load, con
next the spare connector screw in the desired po si
tion before removing the other tap screw from the
original tap position.
I n stan taneo u s R eclo s i n g
The factory adjustment o f the CO unit contacts
provides a contact follow. Where circuit breaker re
closing will be intiated 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. With this change and the contact mounting
screw tightened, the stationary contact w ill rest
solidly against its backstop.
I n stan tan eo u s O vercu rrent U n i t ( 1)
The only setting required is the pickup current
setting which is made by means of t he connector
screw located on the tap plate. By placing the con-
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