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rhe induction unit is the basic unit in all Type lAC rela ys.
mouu,ed in the cradle.
The disk is actuated by a wattmetric type current operating element.
element as used in watthour meters, except the actuating coils·above and below the operating disk are
A capacitor and variable resistor connected in series with the inner coil on the
connected in series.
upper laminated structure makes up the phase-shifting circuit.
which completes the trip or alarm circuit.
contact closing current and its motion is retarded by a permanent magnet acting on the disk to give
correct time delay.
There is a target and seal-in unit mounted on the front to the left of the shaft of the time over-
current unit.
The seal-in unit has its coil in series and its contacts in parallel with the contacts
of the time overcurrent unit such that when the induction unit 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 latches up and remains
exposed until released by pressing a button beneath the lower left corner of the cover.
The instantaneous unit is a small hinge type unit which may be mounted on the front to the right
of the shaft of the time overcurrent unit.
contacts of the time overcurrent unit and its coil is connected in series with the time overcurrent unit.
When the instantaneous unit picks up, it raises a target which latches up and remains exposed until it is
released.
The same button that releases the target of the seal unit also releases the target of the
instantaneous unit.
OVE RCURRENT UNIT
Tr
(atings of the time overcurrent unit are given in Table II.
RELAY
IAC77A and
IAC78A
IAC77B and
IAC78B
Available taps of the time overcurrent unit are shown on Table II.
RAN GE
AMPERES
0. 5 - 4. 0
1. 5 - 12. 0
2. 0 - 15. 0
CONSTRUCTION
These units are o f the induction-disk construction type.
The disk shaft is restrained by a spiral spring to give proper
Its contacts are normally connected in parallel with the
F REQ.
CYCLES
50
60
50
60
0. 5, 0. 6,0. 7,0. 8 , 1. 0, 1. 2, 1. 5 , 2. 0, 2.5, 3. 0,4. 0
1. 5, 2. 0, 2. 5, 3. 0,4.0,5. 0,6. 0, 7. 0,8.0, 10.0, 12. 0
2. 0, 2. 5, 3. 0, 4. 0,5. 0,6. 0, 7. 0,8. 0,10. 0,12. 0,15. 0
GEK-34055
Figs. 2 and 3 show the induction unit
The disk shaft carries the moving contact
RATINGS
TABLE II
PICK U P RANGE, AMPE RES
MAIN (TIME)
INSTANTANEOUS
UNIT
0. 5 - 4.0
1. 5-12.0
2.0-
0. 5 - 4. 0
1. 5 - 1 2.0
2. 0 - 15. 0
10. 0 - 80.0
20. 0 - 160. 0
TA BLE I II
TAPS AVAILABLE (AMPE RES)
4
This is similar to the standard
UNIT
0. 5 - 4. 0
2.0 - 16. 0
�
-
0
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