ABB 41-101U, Instruction Leaflet

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Type CO Overcurrent Relay 41-101U
19
the operating time. Adjust the permanent magnet
keeper until the operating time corresponds to the
value of Table 2.
For type CO-11 relay only, the 1.30 times tap value
operating time from the number 6 time dial position
is 53.5
±
5% seconds. It is important that the 1.30
times tap value current be maintained accurately.
The maintaining of this current accurately is neces-
sary because of the steepness of the slope of the
time-current characteristic (Figure 13). A slight vari-
ation
±
1%, in the 1.3 times tap value current (includ-
ing measuring instrument deviation) will change the
timing tolerance to
±
10% and the effect of different
taps can make the total variations appear to be
±
15%. If the operating time at 1.3 times tap value is
not within these limits, a minor adjustment of the
control spring will give the correct operating time
without any undue effect on the minimum pick-up of
the relay. The check is to be made after the 2 times
tap value adjustment has been completed.
Apply the indicated current per Table 2 for the elec-
tromagnet plug adjustment (e.g., CO-8, 20 times tap
value) and measure the operating time. Adjust the
proper plug until the operating time corresponds to
the value in Table 2. (Withdrawing the left hand plug,
front view, increases the operating time and with-
drawing the right hand plug, front view, decreases
the time.) In adjusting the plugs, one plug should be
screwed in completely and the other plug run in or
out until the proper operating time has been ob-
tained.
Recheck the permanent magnet adjustment. If the
operating time for this calibration point has changed,
readjust the permanent magnet and then recheck
the electromagnet plug adjustment.
6.2.4 Indicating Contactor Switch (ICS)
Close the main relay contacts and pass sufficient dc
current through the trip circuit to close the contacts
of the ICS. This value of current should be not great-
er than the particular ICS tap setting being used. The
operation indicator target should drop freely.
6.2.5 Indicating Instantaneous Trip Unit (IIT)
The core screw must be adjusted to the value of
pick-up current desired.
The nameplate data will furnish the actual current
range that may be obtained from the IIT unit.
6.3 ROUTINE MAINTENANCE
All relays should be inspected and checked periodi-
cally to assure proper operation. Generally a visual
inspection should call attention to any noticeable
changes. A minimum suggested check on the relay
system is to close the contacts manually to assure
that the breaker trips and the target drops. Then re-
lease the contacts and observe that the reset is
smooth and positive.
If an additional time check is desired, pass second-
ary current through the relay and check the time of
operation. It is preferable to make this at several
times pick-up current at an expected operating point
for the particular application. For the .5 to 2.5 am-
pere range CO-5 and CO-6 induction unit use the al-
ternative test circuit in Figure 16 as these relays are
affected by a distorted wave form. With the connec-
tion the 25/5 ampere current transformers should be
worked well below the knee of the saturation (i.e.,
use 10L50 or better).
All contacts should be periodically cleaned. A con-
tact burnisher #182A836H01 is recommended for
this purpose. The use of abrasive material for clean-
ing contacts is not recommended, because of the
danger of embedding small particles in the face of
the soft silver and thus impairing the contact.
7.0 RENEWAL PARTS
Repair work can be done most satisfactorily at the
factory. However, interchangeable parts can be fur-
nished to the customers who are equipped for doing
repair work. When ordering parts, always give the
complete nameplate data.