GE IAC57A - Page 9

Time
Overcurrent
Relays
Type
IAC
GEH
-
1753
INSTANTANEOUS
UNIT
INTRODUCTION
mounted
beside
the
adjustable
pole
piece
.
Time
-
current
characteristics
are
shown
in
Fig
.
10
.
The
instantaneous
unit
is
a
small
instantaneous
hinge
-
type
unit
which
may
be
mounted
on
the
right
front
side
of
the
induction
unit
(
See
Fig
.
7
)
.
Its
contacts
are
normally
connected
in
parallel
with
the
contacts
of
the
main
unit
.
Its
coil
is
connected
in
series
with
the
operating
coil
of
the
main
unit
.
When
the
current
reaches
a
predetermined
value
,
the
instantaneous
unit
operates
,
closing
the
contact
circuit
and
raising
its
target
into
view
.
The
target
latches
in
the
exposed
position
until
released
by
pressing
the
button
beneath
the
lower
left
-
hand
corner
of
the
relay
cover
.
RATINGS
The
instantaneous
unit
is
designed
to
use
either
of
two
coils
having
pickup
ranges
of
10
to
40
,
and
20
to
80
amperes
respectively
.
The
current
-
closing
rating
of
the
contacts
is
30
amperes
for
voltages
not
exceeding
250
volts
.
BURDENS
Burden
data
on
the
instantaneous
unit
coils
are
given
in
the
following
table
:
APPLICATION
Imp
.
Ohms
Volt
Coil
PF
Freq
.
Amp
.
Amp
The
instantaneous
unit
is
used
on
certain
IAC
relay
models
to
provide
instantaneous
tripping
for
current
exceeding
a
predetermined
value
.
10
-
40
60
5
0.83
0.033
0.032
0.027
0.008
0.008
0.007
0.95
50
5
0.80
0.95
25
0.65
5
0.98
OPERATING
CHARACTERISTICS
20
-
80
60
5
0.21
0.95
The
instantaneous
element
operates
over
a
4
to
1
range
and
has
its
calibration
stamped
on
a
scale
50
5
0.20
0.95
25
5
0.15
0.98
CALIBRATION
«
fi
PLATE
ADJUSTABLE
POLE
PIECE
INSTANTANEOUS
UNIT
OPERATING
COIL
SHORTING
COIL
-
CONTACTS
_
TARGET
STATIONARY
CONTACTS
MAIN
COIL
MOVING
CONTACT
ASSEMBLY
A
-
C
TRIPPING
r
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r
Fig
.
7
.
(
8006998
)
Type
IAC
Relay
with
an
Instantaneous
Unit
.
Fig
.
8
.
(
8007060
)
Type
IAC
Relay
with
A
-
C
Tripping
Unit
.
an
7
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