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Type
IAC
Time
Overcurrent Relay
GEH-1788
CALIBRATION
PLATE
ADJUSTABLE
I-.----
POLE PIECE
MS TA N TA N EDUS
UNIT
OPERATING
COIL
TARGET
STATIONARY
[
CONTACTS
MOVING
CONTACT
ASSEMBLY
CONTACTS
SHORTING
COIL
BURDENS
The current-closing rating of the contacts is
30 amperes for
voltages
not exceeding 250 volts.
The current-carrying ratings are affected by the
selection of the tap on the target and seal-in coil
as indicated
in
the following table:
Amperes, a-c or d-c
Function
2-Amp Tap
0.2 Amp Tap
Tripping Duty
30
5
Carry Continuously
3
0.3
Operating Range
2-30
0.2-2
Resistance
0.13
7
Impedance at 60 cy
0.53
52
If the tripping current exceeds 30 amperes an
aaxiliary relay should be used, the connections being
such that the tripping current does not pass through
the contacts or the target and seal-in coils of the
protective relay.
Burdens for the standard coils are given in the
following table.
These are calculated burdens at
five amperes based on burden of minimum tap.
Volt-ampere burdens for the lowest tap on any
of the three coils can be determined for any value
of current, up to 20 times tap setting, from Fig. 6.
Coil
I
Volt
Imp.
Amps
Freq. Tap
Amps
Amps Ohms
PF
4-16
60
4
5
2.0
0.08
0.50
50
4
5
1.7
0.07
0.50
25
4
5
1.3
0.05
0.61
1.5-6
60
1.5
5
14.5
0.58
0.42
50
1.5
5
12.0
0.48
0.42
25
1.5
5
9.0
0.36
0.55
0.5-2
60
0.5
5
105.0
4.20
0.35
50
0.5
5
86.0
3.45
0.34
25
0.5
5
82.0
3.28
0.55
60
0.1
5
3050
122
0.38
0.1-0.4
5tJ
0.1
5
2546
102
0.36
INTRODUCTION
INSTANTANEOUS
UNIT
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. 4). 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.
1•-
C'4
C.,'
cc
0,
LL
c..J
C.,'
cc
MAIN
COIL
A -C
TRIPPING
UNIT
U-
Fig.
L
Type
AC Relay with an Instantaneous Unit
(Front View)
Fig. 5
Type IAC Relay with an A—C Trip Unit
(Rear View)
5
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