UNDERCURRENT AND OVERCURRENT RELAYS
TYPE lAC
INTRODUCTION
These instructions are a supplement to instruc
tion book GEH-1753 which is included in this book.
The combination of the two form complete instruc
tions for the Types IAC59A, IAC59B and IAC59C
relays.
The Type IAC59A relay is similar in construc
tion and operation to the Type IAC51A relay, des
cribed in the included instructions, except that it
has double throw contacts with a seal-in unit for
each contact. The left-hand contacts are adjusted
to close at tap value of current while the right-hand
contacts may be adjusted to close from 50 to 95
percent of tap value.
The Type IAC59B relay is similar to the Type
IAC59A relay except that it is a short time relay
adjusted to close its right-hand contacts when the
current is reduced to tap value. The left-hand con
tact may be adjusted to close from 105 to 150 per
The Type IAC59C relay is similar to the Type
IAC59A relay except that the seal-in units are
omitted.
BURDENS
Burdens for the various relay ratings at mini
mum pick-up current and 60 cycles are given in the
following table:
Min-
Cont.
Relay
Tap
Pick-
Cur-
Volt-
Imp.
P.F.
rent
Ohms
IAC59A
0.5-2
0.5
5
1.17
4.71
.27
IAC59C
1.5-6
1.5
15
1.17
0.52
.25
4-16
4.0
15
1.36
0.08
.38
IAC59B
0.5-2
0.5
2.5
4.72
18.90
.29
1.5-6
1.5
7.5
4.68
2.08
.26
4-16
4.0
15
4.92
0.31
.27
cent of tap value.
INSTALLATION
MOUNTING
The outline and panel drilling dimensions for
these relays are shown in Fig. 6 of this supplement.
CONNECTIONS
Internal connection diagrams are shown in fig.
3 and Fig.
4
inclusive.
ADJUSTMENTS AND TESTS
With connections as shown in Fig. 5 pickup ad
justments and time checks may be made.
The relay is energized for pickup or dropout
check by closing Sl. Unless otherwise requested
the IAC59A is set at the factory to close its right
contacts at
80%
of tap value and the IAC59B is set
to close its left contacts at 110% of tap value.
If
it
is desired to change this percentage or contact
spread, the following procedure is necessary.
Turning the spring-adjusting ring, as described
under "current setting" of the included instructions,
affects primarily the current required to close the
left contacts. Rotating the right-hand moving con
tact, after loosening the clamping screws holding it
in place, changes the current required
to
close the
right contacts. Each of these adjustments affects
the other, hence simultaneous adjustment for clos
ing left and closing right must be made
to
obtain the
desired contact spread.
The relays are adjusted at the factory
to
give
the time characteristics shown in Fig. 1 and Fig. 2.
The time may be changed slightly by changing the
position of the permanent magnet on its supporting
shelf.
In
general, moving the magnet toward the
back of the relay decreases its time of operation.
To check overcurrent time, suddenly apply the
desired preset current to the relay by closing S1.
The time read on the timer is that required to close
the left contacts.
To check the undercurrent
time
close S1 and
S2 and, using
Rl,
adjust the current to a value
greater than that required to close the left-hand
contacts. With S2 open, use
R2
to set the current
to the desired value below the current required to
close the right-hand contacts. Then with S1 and S2
both closed, open S2. The time read on the timer is
that required for the right contacts to close when the
current is suddenly reduced from a value sufficient
to close the left-hand contacts, to a predetermined
value.
These instructions do not purport to cover all details or variations in equipment nor to provide for
every
possible
contingency to be met in connection with installation,
operation or maintenance.
Should
further information be desired
or
should particular pro
bl
ems arise which are no t covered sufficiently for
the
purchaser's purposes, the matter should
be
referred
to
the General Electric Company.
To
the extent
required
the
products described herein meet applicable ANSI,
IEEE and NEMA standards;
but
no such assurance is given with respect to local codes and ordinances because
they
vary
greatly.
3
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