GE IAC51A User manual

INSTRUCTIONS
TIME-OVERCURRENT RELAYS
TYPES
IAC51A IAC52A
IAC51B
IAC51R
IAC52 B
GENERAL _ ELECTRIC
GEH-1753J

GEH-1753 Time Overcurrent Relays Type IAC
2
TOP PIVOT ________ '-
TAP PLUG -----~~1f~II .. ~~~~~ .... --~~~;=:
SEAL-IN UNIT
HOLDING COIL
/""---TAP
BLOCK
SEAL-IN
~--"--_f_':-=Hrr_TI ME DIAL
TARGET-
._------+::-:
SEAL-IN UNIT
STATIONARY
CONTACT, LEFT
SEAL-IN UNIT
STATIONARY
CONTACT, RIGHT
SEAL -IN
MOVING
CONTACT
ASSEMBLV-- -, •
It 'III "'M"~ Io;f'S
~ ,!"'$T"'t.lLl1Qlt,fa
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DISK
AND
SHAFT
LOWER
JEWEL SCREW
<&.1
A - (8006996) Front View
B - (8006997) Rear Vie,,,
DISK
DRAG
"---1-- MAGNET
Figure 1. The 1nduction lnit for Type lAC Relayso

TIME-OVERCURRENT
TYPE lAC RELAYS
INTRODUCTION
Type
Contact Instantaneous
AC Trip Induction
Outline & Internal
Circuits Unit
IAC51A(-)A One
NQ
IAC51B(- )A
One
Yes
IAC51R(- )A
One
Yes
IAC52A(-)A Two
No
IAC52B(- )A
Two
Yes
The Type lAC relays comprise a group of relays
that are employed to protect against overcurrent on
single-phase and polyphase circuits. The various
relays in this lAC group are identified by model
numbers, and the relays differ in the number of
circuits they close, the length of time delay and
features that are determined by the characteristics
of the protected circuit.
These relays consist of an induction unit or an
induction unit with an instantaneous unit which
Unit Unit
Panel Drilling
Connection
No One Fig. 18
Fig. 11
No
One
Fig. 18
Fig. 12
Yes
One
Fig. 18
Fig. 13
No
One
Fig. 18
Fig. 14
No
One
Fig. 18
Fig. 15
permits instantaneous tripping for extremely high
currents, or an induction unit with an a-c tripping
unit for use where d-c power is unavailable or a-c
tripping is preferred. Since practically all lAC
relays are composed of various combinations of the
above - that is, the induction unit, the instantaneous
unit and the a-c tripping unit - they are for con-
venience, described separately in the following text.
The above table indicates the units comprising each
type and also lists the internal connections and out-
line and panel drilling diagrams.
INDUCTION
UNIT
INTRODUCTION
The induction unit is the basic unit in all lAC
relays. Fig. 1 shows the induction unit mounted in
the cradle. These units are of the induction-disk
construction type. The disk is actuated bya current
operating coil on a laminated U-magnet. The disk
shaft carries the moving contact which completes
the alarm or trip circuit when it touches the station-
ary contact or contacts. The disk shaft is restrained
by a spiral spring to give the proper contact-closing
current and its motion is retarded by a permanent
magnet acting on the disk to give the correct tilne
delay.
There is a seal-in unit mounted on the front
to the left of the shaft. This unit has its coil in
series and its contacts in parallel with the main
contacts such that when the main contacts close the
seal-in unit picks up and seals in. When the
seal-in unit picks up, it raises a target into view
which tatches up and remains exposed until released
by pressing a button beneath the lower left corner
of the cover.
APPLICATIO N
The induction unit is the main unit in all lAC
relays, supplying the inverse time delay character-
istics of the relay and sounding an alarm or tripping
the breakers for overload currents which cause it
to close its contacts.
OPERATING CHARACTERISTICS
The induction unit may have one or two circuit-
closing contacts which close as the current increases
to the pick-up value as set on the tap block. The
time delay in closing the contacts is determined by
the setting of the time dial (Fig. 1). The time-current
characteristics are shown in Fig. 2.
RATINGS
The induction element is designed to use any
one of three operating coils, each having a different
combination of taps as follows: 4, 5~ 6, 8, 10, 12
and 16 amperes; 1.5, 2.0, 2.5, 3.0, 4.0, 5.0 and 6.0
amperes; 0.5, 0.6, 0.8, 1.0, 1.2, 1.5 and 2.0 am-
peres.
Tilese instructions do not purport to cover all details or variations in equipment nor to provide for
every possihle contingency to be met in connection with installation, operation or maintenance. Should
further information he desired or should particular problems arise which are not 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 JlO such assurance is gi ven wi th respect to local codes and ordinances because they vary greatly.
3

GEH-1753 Time Overcurrent Relays Type lAC
4
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.1 .1 .1 .8 .8 1 2 3 4 II • 1 •• 10
20
30 40 50 80 7080 DO!
MULTlPLES OF RELAY TAP SETTING
Fig.2. (088880269 [3) Time-current Curves of Type lAC Relays with Inverse-time Characteristics

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:
DUAL RATED
0.2/2.0 0.6/2.0
0.2 2.0
0.6
2.0
Carry 30 amps for
(sec)
0.05 2.2
0.5
3.5
Carry 10 amps for
(sec) 0.45
20 5.0
30
Carry continuously
(amp)
0.37
2.3
1.2
2.6
Minimum operating
(amp)
0.2
2.0 0.6 2.0
Minimum dropout
(amp)
0.05
0.5 0.15 0.5
DC resistance
(ohms)
8.3 0.24
0.78 0.18
60 hertz impedance
(oh'TIs) 50
0.65
6.2
0.65
50 hertz impedance
(ohms)
42 0.54 5.1 0.54
If the tripping current exceeds 30 amperes, an
auxiliary 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.
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Time Overcurrent Relays Type lAC GEH-1753
BURDENS
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. 3.
Coil
Amperes
4-16
1.5-6.0
0.5-2.0
I
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/
/
/
/ /
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/
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/
./
L V
V
f-;::: ~
::--
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- --:::::
""""'"
Freq.
60
.....
50
'"
60
50
25
60
50
25
60
50
25
TAP
RANGE
.5-2.0
TAP
25"']
RANGE
60~ 1. 5-6. 0
50", ANPS.
]
TAP
60"'jRANGE
25", 4-16
50ft. ANPS.
Tap
Volt-
Imp.
PF
Amps
Ohms
4.0
8.8 0.35
0.29
4.0
8.0
0.32 0.31
4.0 7.5
0.30 0.36
1.5
59.0
2.36 0.26
1.5
52.0 2.08
0.28
1.5
48.0
1.92 0.34
0.5
530.0 21.2 0.26
0.5
470.0
18.8 0.28
0.5 430.0 17.2
0.34
o 4 6 8 10 12 14 16 18 20
MULTIPLES OF MINIMUM TAP SETTING
SATURATION CuRVES AT VARIOUS FREQUENCIES
FOR 3 TAP RANGES OF THE TYPE IACS1A RELAY
LOWEST TAP USEO IN ALL CASES
Fig. 3. (K-6306891-1) Saturation Curves for Lowest laps ',f the Induction Unit
of Type lAC Relays \vith Inverse-time r,haractcrislics.
5

GEH-1753 Time Overcurrent Relays Type IAC
50
51
DEVICE FUNCTION NUMBERS FOR USE
WITH ALL EXTERNAL DIAGRAMS
Instantaneous Unit
Overcurrent, Relay, Type IAC
51N -Ground Overcurrent Relay, Type lAC
52 Power Circuit Breaker
SI Seal-in Unit, with Target
TC
A
!
Trip Coil
Auxiliary contact, closed when breaker
closes.
A-C BUS
1
2
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t-
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rRIPPI~G -~
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~ACTOR- ;
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l ~ t;T
-=-
1 1
Fi
6. 5
(K6375668-l) External Connections of Three
Type IAC51A Relays used in Conjunction with Tripping
Reactors for Protection of aTThree-Phase Circuit.
6
A_C BuS
1"I~rRIP BUS
W ll::2
ll=l
ill
ll.::l
I-I
28 t t
L
52
#
Fig. 4 (K-6375667-2) External Connections of Three
Type IAC5lA Relays used for Phase-to-Phase and
Ground Overcurrent Portection of a 3-Phase Circuit.
A-C Bus
Fig. 6 (K-6375669-6) External Connections of Three
Type IAC5lR Relays used for 3-Phase Circuit Protection.

Time Overcurrent Relays Type IAC GEH-1753
INSTANTANEOUS UNIT
INTRODUCTION
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 apredetermined value,
the instantaneous unit operates, closing the contact
[ircuit 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.
APPLICATION
The instantaneous unit is used on certain IAC
relay models to provide instantaneous tripping for
current exceeding a predetermined value.
OPERATING CHARACTERISTICS
The instantaneous element operates over a 4 to
1 range and has its calibration stamped on a scale
; ..
OPEAATING
COIL
.. TARGET
STATIONARY
CONTACTS
Fig. 7. (8006998) Type lAC Relay with an
Instantaneous Unit.
mounted beside the adjustable pole piece. Time-
current characteristics are shown in Fig. 10.
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:
Coil Freq. Amp.
Volt
Imp.
Amp Ohms
10-40
60 5
0.83 0.033
50 5
0.80 0.032
25 5
0.65 0.027
20-80 60 5 0.21
0.008
50 5
0.20
0.008
25 5 0.15
0.007
SHORTING
COIL
---+-+--1:
MAl N -~~-.'--f---J
COIL
•
.. -=
Fig. 8. (8007060) Type lAC Relay with an
A-C Tripping Unit.
PF
0.95
0.95
0.98
0.95
0.95
0.98
-
7

8
GEH-1753
Time Overcurrent Relays Type IAC
A-C TRIPPING UNI1
INTRODUCTION
The a-c tripping unit is a Type REA relay unit
designed to energize a circuit breaker trip coil from
its assoc iated current transformer upon the operation
of the main unit of the IAC relay. It transfers the
current from the secondary of the current trans-
former into the trip coil and removes the current
from the trip coil when the breaker trips.
The tripping unit is mounted on the rear of the
frame opposite the tapped operating coil of the
induction unit (see Fig. 8). The operation of this
unit is illustrated in Fig. 9. The secondary current
circulates through the induction unit current coil
and the main coil of the REA auxiliary tripping unit,
returning through the REA contacts to the current
transformer. Normally, most of the flux generated
by the main REA coil passes through the upper limb
of the magnetic structure and holds the armature
firmly against this limb. When the contacts of the
induction unit close, the shorting coil of the REA is
short-circuited and current flows in this coil by
transformer action, causing a redistribution of flux
which actuates the armature and the REA contacts.
The opening of the REA contacts causes the secondary
current to flow through the trip coil which trips the
breaker.
0.030
0.025
•
~
en
0.0.20
I
&.U
::I
..-
O.Ol~
Q..
:;)
J:
u 0.010
CL
0.005
0 0 1 2 4
CURRENT
TRANS
16S1
BREAKER
TRIP COIL
L
AC TRIP UNIT
NORMALLY
CLOSlO
.-----------.:::1 oc;:;----+------<~ CONT ACTS
o
At:. TRIP UN~T
SHORTlhG
COIL
1-- __ -' ,..._-+_r=~~~r-::::::::t::J AC TRIP' UN IT
MAIN COIL
Figo 9 (K-6l54766-2) Diagram Illustrating Operatio~
of Type lAC Relays having an A-C Tripping Unit.
OPERATI NG TIME
RANGE FOR N4Y
PI CKUP SETIING
6 7 b 10
MULTIPLES Of PICK-UP
Fig. 10 (6306872 [5])
Time-current Characteristics of Original Instantaneous Unit

APPLICATION
The a-c tripping unit is used in Type IAC relays
where a reliable direct-current tripping source is
not available and it is necessary to trip the breaker
from the current-transformer secondary.
RATINGS
The a-c tripping unit has a continuous rating of
five
amperes but will operate on a minimum current
of 3.5 amperes. They should be used with three-
ampere trip coils. The contacts of these units will
transfer current transformer secondary current up
to 100
amperes. For applications where the second-
ary current exceeds 100 amperes, the REAllB relay,
Time Overcurrent Relays Type IAC GEH-1753
which
has contacts rated 200 amperes, can be used
in conjunction with IAC overcurrent relays. The
REAllB is not mounted inside the IAC case.
BURDENS
Burdens of the REA unit are given in the
following table:
Frequency
Amp
Impedance
PF
Volt-
in Ohms
Amperes
60 5 0.49 0.80 12.2
50 5 0.33 0.85 8.4
25
5 0.23 0.62 5.8
RECEIVING, HANDLING AND STORAGE
These relays, when not included as a part of a
control panel, will be shipped in cartons designed
to ~rotect them against damage. Immediately upon
receipt of the relay, an examination should be made
for any damage sustained during shipment. If
injury or damage resulting from rough handling is
evident, a claim should be filed at once with the
transportation company and the nearest Sales Office
of the
General Electric Company notified promptly.
Reasonable care should be exercised in un-
SEAL-IN ~ UNIT ""'- I
D INDUCTION
UNIT
'"
l 1
f1
1
2 6
INTERNAL CONNECTIONS (FRONT
VIEW)o=SHORT FINGER
Fig. 11. (K-6209658-10) Internal Connections fo:
the Type IAC51A Relay (Front View).
packing the relay in order that none of the parts are
injured or the adjustments disturbed.
If the relays are not tobe installed immediately,
they should be stored in their original cartons in a
place that is free from moisture, dust, and metallic
chips. Foreign matter collected on the outside of
the
case may find its way inside when the cover is
removed and cause trouble in the operation of the
relay.
2
INDUCTION
UNIT
INSTANT
UNIT
6
SHORT FINGER
Fig. 12. (K-6209661 [11) Internal Connections for
the Type IAC51B Relay (Front View)
9

GEH-1753 Time Overcurrent Relays Type IAC
10
SEAL-IN
iJ t; :
1
I
N U
S N
T :
A T
N
T
INDUCTION
Uf'i:-:-
I ~ I f1 ~ I ~ I
2 4 6 8 10
A-C -;RIP
- UN IT
INSTANT.
UU:
Fig. 13 (K-6209294-3) Internal Connections for the Type IAC5lR Relay (Front View)
SEAL-IN
UNIT
SI
INDUCTION
2
INDUCTION
UNIT
6
SHORT FINGER
Fig. 14 (K-6209662 [5]) Internal Connections for the Type IAC52A Relay (Front View)