GE IAC53A

Type IAC Time Overcurrent Relay GEH-1788
MAINTENANCE
DISK AND BEARIN~S
The lower jewel may be tested for cracks by
exploring its surface with the point of a fine needle.
The jewel should be turned up until the disk is
centered in the air gaps, after which it should be
locked in this position by the set screw provided
for this purpose.
CONTACT CLEANING
For cleaning fine silver contacts, a flexible
burnishing tool should be used. This consists of a
flexible strip of metal with an etched roughened
surface, resembling in effect a superfine file. The
polishing action is so delicate that no sc;ratches are
left, yet corroded material will be removed rapidly
and thoroughly. The flexibility of the tool insures
the cleaning of the actual points of contact.
Fine silver contacts should not be cleaned with
knives, files, or abrasive paper or cloth. Knives or
files may leave scratches which increase arcing and
deterioration of the contacts. Abrasive paper or cloth
may leave minute particles of insulating abrasive
material in the contacts and thus prevent closing.
The burnishing tool described is included in the
standard relay tool kit obtainable from the factory.
PERIODIC TESTING
It is recommended that pickup of all units be
checked at least once every six months.
ACCEPTANCE TESTS
ELECTRICAL
A. MAIN UNIT
Pickup
Set the relay at the 0.5 time dial position and
minimum tap. Using the test connections of Figure
19 the main unit should close its contacts within
± 5% of tap value current.
Time Test
Set the relay at the 5.0 time dial position and
minimum tap. Using the test connections of Figure
19, and applying 5 times pickup current, the relay
should operate at 1.31 seconds ±7%. With 2 times
pickup current applied the operating time should be
7.21 seconds ±7%. With 10 times pickup current
applied the operating time should be 0.72 seconds
±7%.
B. INSTANT ANEOUS UNIT
Pickup
With gradually applied current the unit should
pickup at ±10% of the minimum calibration. There
should be no more than ±5% variation on repeated
pickup checks. Be sure the target has been reset
after each test.
c. TARGET SEAL IN UNIT
Pickup
The unit should pickup between 75 and 100% of
tap value with the main unit contacts closed.
Dropout
Open the main unit contacts, the seal in unit
should remain picked up. Reduce the currentto 25%
of tap value; the unit should drop out.
RENEWAL PARTS
It is recommended that sufficient quantities of
renewal parts be carried in stock to enable the
prompt replacement of any that are worn, broken,
or damaged.
When ordering renewal parts, address the
nearest Sales Office of the General Electric Com-
pany, specify the quantity required and describing
the parts by catalogue numbers as shown in Renewal
Parts Bulletin No. GEF-3883.
15