GEK-65514
TIME OVERCURRENT RELAY
TYPE IAC51V
INTRODUCTION
These instructions are a supplement to instruction book GEH-1753. The combination of the two books
form instructions for the Type IAC51V relay.
These relays provide for a target seal-in unit for both the time overcurrent element and the instan
taneous overcurrent unit. The Type IAC51V relay is similar to the Type IAC5IA relay with the addition of
a right hand target and seal-in unit, and a high-dropout instantaneous unit mounted in the rear of the
relay unit.
The special high-dropout instantaneous unit is constructed without a target and is designed to yield
dropout values of 80 percent, or higher, of pickup current.
The pole piece is constructed and secured
with a special wave washer so that it can be rotated to the most favorable position. The unit may be
calibrated in the standard manner once the pole piece has been adjusted for 80 percent dropout or higher.
HIGH-DROPOUT INSTANTANEOUS UNIT
The high-dropout instantaneous unit contacts will close 30 amperes at voltages less than 250 volts.
The coil ratings available are shown in Table I.
TABLE I
RATINGS OF HIGH-DROPOUT INSTANTANEOUS UNIT COILS
PICKUP RANGE
CONTINUOUS
ONE SECOND
(AMPS)
RATING (AMPS)
RATING (AMPS)
0.5 - 1.5
0.75
12
1.0 - 3.0
1.5
25
2.0 - 6.0
3.0
50
4.0 - 12
6.0
100
10 - 30
15.0
200
20 - 60
30.0
320
The high-dropout instantaneous unit is similar to the standard instantaneous unit
except
it has no
target, and dropout current is
approximately 80 - 90
percent of the pickup current.
Fig. 2 is a picture
of the high-dropout unit.
The adjustable core (A} sets the pickup level.
Turning the core down (clockwise, top view) lowers
the pickup, while t�rning the core up (counterclockwise, top view) increases the pickup.
Before attempt
ing to turn the core, the locknut (B) must be loosened. After adjusting the core, the locknut must be
retightened. When loosening or tightening the locknut, the sleeve (C) to which the shading ring (D) is
attached must be held to prevent it from turning. Rotation of the shading ring sets the dropout level
and thereby determines the quietness of operation in the picked up position.
The core has been factory
set
to obtain
80
percent dropout at the minimum setting and approximately 90 percent dropout at the
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 inst allation, operation or maintenance.
Should
further information be desired or should particular problems arise which are not covered sufficiently for
the purch aser's purposes, the matter should be referred to the General Electric Company.
To the extent req uired the p roducts 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.
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