ABB CKO-5, Manual

Page: 16 / 24

41-101.3A Type CKO Overcurrent Relay
16
4.3 Instantaneous Overcurrent Unit (I)
The only setting required is the pickup current setting
which is made by means of the connector screw lo-
cated on the tap plate. By placing the connector
screw in the desired tap, the relay will just close its
contacts at the tap value current.
CAUTION
!
Since the tap block connector screw carries op-
erating current, be sure that the screw is turned
tight.
In order to avoid opening current transformer
circuits when changing taps under load, the re-
lay must first be removed from the case. Chassis
operating shorting switches on the case will short the
secondary of the current transformer. The taps
should then be changed with the relay outside of the
case and then reinserted into the case.
4.4 Indicating Contactor Switch (ICS/I
and ICS/T)
The setting required on the ICS units is the selection
of the 0.2 or 2.0 ampere tap setting. This selection is
made by connecting the lead located in front of the
tap block to the desired setting by means of the con-
necting screw.
5.0 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 rear mounting stud or
studs for the type FT projection case or by means of
the four mounting holes on the flange for the semi-
flush type FT case. Either the stud or the mounting
screws may be utilized for grounding the relay. Ex-
ternal toothed washers are provided for use in the lo-
cations shown on the outline and drilling plan to fa-
cilitate making a good electrical connection between
the relay case, its mounting screw or studs, and the
relay panel. Ground wires should be affixed to the
mounting screws or studs as required for poorly
grounded or insulating panels. Other electrical con-
nections may be made directly to the terminal by
means of screws for steel panel mounting or to the
terminal stud furnished with the relay for thick panel
mounting. The terminal stud may be easily removed
or inserted by locking two nuts on the stud and then
turning the proper nut with a wrench.
For detail information on the FT case refer to I.L.41-
076.
6.0 ADJUSTMENTS AND MAINTE-
NANCE
The proper adjustments to insure correct operation
of this relay have been made at the factory. Upon re-
ceipt of the relay, no customer adjustments, other
than those covered under Section 4, Settings,
should be required.
6.1 Performance Check
The following check is recommended to insure that
the relay is in proper working order.
6.1.1 Instantaneous Overcurrent Unit (I)
a. Contact Gap
The gap between the stationary and moving con-
tacts with the relay in the de-energized position
should be approximately .020".
b. Minimum Trip Current
The pick-up of the overcurrent unit can be checked
by inserting the tap screw in the desired tap hole and
applying rated tap value current. The contact should
close within
±
5% of tap value current.
6.1.2 Time Overcurrent Unit (CO)
a. Contacts
The index mark on the movement frame will coincide
with the "0" mark on the time dial when the stationary
contact has moved through approximately one-half
of its normal deflection. Therefore, with the station-
ary contact resting against the backstop, the index
mark is offset to the right of the "0" mark by approxi-
mately .020". The placement of the various time dial
positions in line with the index mark will give operat-
ing times as shown on the respective time-current
curves.
b. Minimum Trip Current
Set the time dial to position 6, alternately apply tap
value current plus 3% and tap value current minus
3%. The moving contact should leave the backstop
at tap value current plus 3% and should return to the
backstop at tap value current minus 3%.