GE IAC60A Instructions Manual page 14

GEH-1753
Time Overcurrent Relays Type lAC
INTRODUCTION
The a-c tripping unit is a Type REA relay unit
designed to en ergize a circuit breaker trip coil from
its associated current transformer upon the operation
of the main unit of the lAC relay.
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.
unit is illustrated in Fig.
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.
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.
0.0;30
0.025
.
�
O.C'r20
&.U
1-
{).0!5
0..
�
0
0.010
0 .005
0
0
Fig.
8
A·C TRIPPING
It transfers the
8). The operation of this
9. The secondary current
When the contacts of the
l 2
t.lJL T I PLES Of PI CK-uP
10 (&30&872
[S])
Tl.me-current Characteristics
UNI1
CURRENT
TRANS
9
(K-6154766-2)
Fig.
lAC
of Type Relays having an
OPERATI NG TIME
RANGE FOR
Nff
PICKUP
SETT I NG
6 7
of
Original Instantaneous Unit
laS I
BREAKER
TRIP COIL
TRIP UH�T
AI:.
::HORT I PiG
COIL
AC TRII" UNIT
CO' I L
MAIN
Diagram Illustrating Operation
A-C
Tripping Unit.
10