GE AK-50 - Selective Tripping and Disconnects; Selective Tripping Principles; Primary Disconnects (AK-50); Secondary Disconnects Function and Replacement

Gil
-
74600
Low
-
voltage
Power
Circuit
Breakers
)
SELECTIVE
TRIPPING
Selective
tripping
is
obtained
when
the
breakers
in
the
electrical
distribu
-
tion
system
are
arranged
on
the
basis
of
a
progressive
series
of
time
and
current
pickup
.
This
will
allow
the
breaker
having
the
shorter
time
set
-
ting
and
the
lower
pickup
to
trip
before
the
breaker
having
the
longer
time
set
-
ting
and
the
higher
current
pickup
,
pro
-
vided
the
fault
is
on
the
part
of
the
line
protected
by
the
breaker
having
the
lower
setting
.
Hence
,
if
a
fault
oc
-
curs
in
any
part
of
the
electrical
sys
-
tem
,
only
the
breaker
nearest
the
fault
will
trip
.
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8
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^
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%
TO
ID
TOCS
MLAKCft
RATING
2
N
In
order
to
reduce
the
possibility
of
damaging
the
equipment
and
to
pro
-
vide
maximum
safety
to
the
operator
,
the
overload
caused
by
a
fault
is
re
-
moved
in
a
minimum
amount
of
time
by
selective
tripping
.
Overloads
pro
-
ducing
current
up
to
five
or
ten
times
the
breaker
rating
are
removed
in
a
matter
of
a
few
cycles
while
currents
in
excess
of
this
value
are
removed
instantaneously
.
2
T
-
TDJE
Ui
RCKT
TME
N
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NYWraMEOUS
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«
CT
M
FAC
TOFT
—
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TO
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TMC
8
-
KIKE
*
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-
f
-
i
TMC
A
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8
TA
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—
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FACTORY
-
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.
CM
0115
SECONDS
(
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,
OR
tC
RESPECTIVELYI
AT
NVV
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OF
SNORT
TMC
\
V
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MOA
-
UR
$
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M
L
^
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-
02
.
01
fr
“
i
2
5
4
BO
100
tOO
CURRENT
IN
TIMES
BREAKER
RATING
4
HI
B
CURRENT
IN
TIMES
BREAKER
RATING
For
the
exact
characteristics
and
setting
of
each
breaker
in
a
selective
system
,
reference
should
be
made
to
the
coordination
chart
furnished
for
the
particular
system
.
Fig
.
29
.
Typical
time
-
current
characteristics
BREAKER
ACCESSORIES
PRIMARY
DISCONNECTS
AK
-
50
ONLY
at
the
top
rear
of
the
breaker
.
A
ter
-
minal
board
serves
the
same
purpose
on
stationary
mounted
and
general
pur
-
pose
enclosure
mounted
breakers
.
These
secondary
disconnects
allow
re
-
moval
of
the
breaker
without
the
neces
-
sity
of
having
to
detach
external
con
-
nections
.
The
movable
part
of
the
secondary
disconnects
consists
of
an
insulating
body
which
holds
a
conducting
spring
-
loaded
plunger
to
which
a
flexible
lead
is
attached
.
As
the
breaker
moves
in
-
to
its
enclosure
,
the
plunger
is
de
-
pressed
by
sliding
onto
the
stationary
disconnects
of
the
enclosure
.
REPLACEMENT
1
.
Unfasten
disconnect
body
from
breaker
cross
-
channel
.
REPLACEMENT
If
for
any
reason
the
disconnects
must
be
replaced
or
removed
,
the
po
-
sition
of
the
nuts
on
the
bolts
should
be
carefully
noted
and
the
number
of
turns
of
the
nuts
should
be
counted
,
so
that
in
reassembly
the
original
amount
of
compression
can
be
restored
by
re
-
placing
the
nuts
to
their
former
posi
-
tion
on
the
bolts
.
The
primary
disconnects
should
always
be
kept
lubricated
with
G
.
E
.
Co
.
D
50
H
47
grease
.
The
primary
disconnects
are
at
-
tached
to
the
circuit
breaker
studs
at
the
rear
of
the
breaker
base
.
Each
disconnect
assembly
consists
of
four
pairs
of
opposed
contact
fingers
.
The
contact
fingers
are
secured
to
the
breaker
stud
by
two
bolts
which
pass
through
the
assembly
and
the
stud
.
When
engaged
with
the
stationary
stud
of
the
enclosure
,
the
disconnect
fingers
exert
a
set
amount
of
force
against
the
stationary
stud
through
the
action
of
the
compression
springs
.
Retainers
and
spacers
hold
the
contact
fingers
in
cor
-
rect
alignment
for
engagement
with
the
stud
.
The
amount
of
force
which
the
^
fingers
exert
against
the
studisdeter
-
Jmined
by
the
degree
to
which
the
RnrincR
art
*
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HvthoHnH
unH
SECONDARY
DISCONNECTS
The
secondary
disconnects
for
all
breakers
serve
as
connections
between
breaker
control
circuit
elements
and
external
control
circuits
.
They
are
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.
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