Power Sensor Trip - General Description; Reverse Current Tripping Device - Ak-50 Only - GE AK-2-50 Maintenance Manual
Low-voltage power circuit breakers
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Also See for AK-2-50:
- Maintenance instructions manual (48 pages) ,
- Installation and operation manual (7 pages) ,
- Installation and operation manual (10 pages)
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REVERSE CURRENT TRIPPING DEVICE
AK-50 ONLY
(Fig. 31}
The
device is enclosed in a molded case and
is
mounted on the right pole base
simila.
r to
the.
series overcurrent tripping device.
The
reverse -current
tripping
device
(see
Fig. 28}
consists of a
series coil
(2} with an iron core mount-
ed between two pole pieces
(9),
also a potential
coil (7) connected across a constant source
of
voltage
and
mounted
around a
rot;ary·-type
arm-
ature (10). Calibration
spring
(6)
determines the
armature pick-up when
a
reversal
of
current
occurs.
As
long as
the flow
of ~urrent throug_h the
breaker is
in
the normal direction, the
magnetic
flux
of
the
series coil and
the
magnetic
flux
of the
potential coil produce
a torque
which
tends to
rotate the
armature counterclockwise.
The
calib-
ration
spring
also
tends
to rotate the
armature in
the same
direction.
This
torque causes the
armature to
rest
against the stop screw
(12)
attached
to a bearing
plate on
the
right
side of
the
device.
If
the current
through
the series coil
(2)
is
reversed, the armature
(10)
tends to move in the
clockwise direction against the restraint
of
the
calibration spring (6). When the current reversal
exceeds
the calibration
setting,
the
armature
-
revolves clockwise causing the trip rod
(3)
to
move
upwa.
r d engaging the trip paddle (1), there-
by tripping
the
breaker.
ADJUSTMENTS
(Fig.
31)
The
only adjustment
to
be made
on
the
rever~e
current
device is
-
to
make sure that the trip
rod has a minimum
overtravel of 1/32 in. beyond
the point
of
tripping the breaker.
This
adjus!me~t
should have
to
be
made
only when an
old
device is
bei_ng rep~aced
by a new
one.
·
The
new
device will be
factory
adjusted
so
that
the top
end of
the
trip.
rod
(3) will-extend 1/2
-in. above the
top
of
the
device
case,
and no addi-
tional adjust.ments of the
trip rod should
be
required.
To obtain
the
proper
1/32
in. over-
travel,
cl~se
the
break~r ~d proceed as follows:
1.
Loosen
the
locking nut
(2B).
2.
Manually
lift
the
trip rod
and vary
the
.
position of
the
adjusting
nut
(2A},
this
establish-
ing the position of
the adjusting
nut
where
the
breaker is just
tripped.
NOTE:
Be sure to keep clear
of
moving
breaker
parts
when tripping
the
breaker.
3.
With
this
position of
the
adjusting nut
established,
advance
the adjusting
nut upward
one
and
one-half
turns.
4.
Tighten the locking nut and the
mfnimum
1/32-in.
overtravel of the trip
rod
should be
obtained.
Low Voltage Power Circuit Breakers GEK-7303
REPLACEMENT
(Fig. 31)
After removing the wiring
for the
potential
coil the
reverse
current device can
be
removed
and replaced by following the procedure outlined
for replacing the
series
overcurrent device.
For
wiring,
see Fig. 31).
POWER SENSOR
T
RIP
GENERAL
DESCRIPTION
All
AK-3 Type
Air
Circuit Breakers contain
Power Sensor Overcurrent
Trip
Devices.
The
Power
Sensor Trip functions with
solid
state
components .with the
exception of
the
Solenoid
Trip which is used to trip the
breaker
on
signal
from the Power
Sensor
Unit.
The
Power
Sensor
Overcurrent Trip
Device consists of
four
major
components.
1.
The
magnetic coils around
the
breaker
conductors (Fig. 32
&
33).
2.
The
Power Supply which provides both
the tripping energy
and the
comparison basis
for
overcurrent
detection (Fig.
34).
·
3.
The
Power Sensor Unit with the various
pick-up settings and time delay selection taps
(Fig.
35}.
-
4.
The trip
solenoid which physically trips
the breaker
(Fig.
36}.
In
addition
to the
phase
overcu_
r rent protection,
a
ground fault
sensing
feature
may
be provided.
The
Ground Sensing
Device
works
on the principle
that the instantaneous value of
current
flowing
in
the three conductors (or; in
four
condu_
c tors on four
wire
systems) must add
to
zero unless
gro_und
current is
flowing.
~
Therefore,
if
the
electrical
system
is
a four wire wye system with the
neut~al
grounded at the transformer, the fourth sensing
coil Fig. 38 must
be included on
the neutral
conductor
with its
secondary combined
with the
secondaries of the
three
phase sensors
which
are
mounted on the breaker. On Draw-out breakers
the output of
the
external
neutral
sensor must enter
the breaker
by
a
control disconnect
which
is
mounted
low and
on the
centerline on the back
of
the breaker. Refer to
Fig.
(37) for
Ppwer
Sensor
Cabling Diagram.
MAINTENANCE
When mal-functioning of
thePower Sensor Trip
is
indicated, the
trouble
should be
traced to
one
or more of these
four
components involved, and
that
component should
be replaced as a unit.
The
following steps should be
taken to detect a mal-
functioning unit.
.-
NOTE:
No adjustment
to·
the taps
controlling
pick-up
should be
made with the breaker
car-
rying
current.
In
the event the
Power Sensor
Device
must
be made
non-operative
to allow the breaker
to
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