GEI-86151
B
INTERCHANGEABILITY
OF
DRAWOUT
BREAKERS
GENERAL
Low-voltage
switchgear
practice
requires that
drawout
breaker elements of the
same ampere frame
size be
physi-
cally
interchangeable.
Electrical interchangeability
of sec-
ondary
and control circuits, of
course, requires
duplicate
wiring. The
four drawout
styles
(AKD,
A, B &
C) of the AKF-75
and
-100
models
satisfy this requirement in varying
degree.
The B and
C types, being of more recent
design, limit inter-
changeability
within
a
given
frame
size to those
units
having
the
same
voltage
rating; rejection
of unwanted types thus is
more selective than that
of the earlier AKD
and AKD-S
models. The individual
interchangeability
patterns
are
illus-
trated
in
Fig. 10.
Because
the AKR-75/100 B
and C
models
are
identical
in
height
and
width,
each
includes
means to
prevent
inadvertent
interchange
of
these
3200 and 4000
ampere sizes.
This is
done
by adding
interference
hardware
to each breaker and its
compartment, causing
the
compartment to accept the correct
breaker type and reject all others.
Rejection
means
are
not required
on the AKD and Code A
breakers; the
-100
frame is
wider than the
-75,
making them
inherently non-interchangeable.
NO.LETTER AKD TYPES
As
the Fig. 10 directional arrows indicate,
all AKD ele-
ments are interchangeable within
each frame
size.
Considering
that the AKR-75 AKD
and
B type
breaker
models
are
identical in
width and
employ
very
similar drawout
mechanisms,
rejection
plates
are
added to the AKD AKR-75
modelsto
preventtheir
insertion into
Btype substructures. See
Fig.
11.
CODE
A
TYPES
Interchangeability is
identical to that
of
the AKD type.
CODE
B TYPES
Interchangeability within
and between
frame
sizes
is
pre-
vented
by
the rejection
system of Fig,
13.
Variously
posi-
tioned
pins
on the drawout tray must align with matching
holes and notches in rejection
plates
bolted to the
breaker's
bottom flanges. An
incorrect
style
breaker
presents
a
mis-
match and will not seat on the tray.
Becaus:tthe
B-type
drawoutmechanism
is
nearly
identical
to.the
AKD
type,
all
B
elements
include
additionat
means
to
rejectthemfrom
AKD
compa.rtments,
e,n
iiiigger
Oracfuet
i
attached
to
the
riqht
edoe
of
the
re"rlr"r;;l;""r.h
B
breaker
per
Fis.
1
2.
rh
is
interfe;es
with
th;;";;
;;;
o'iine
risnt
warr
of
the
AKD
compartment
".d
;;;;;;i:;iffi
the
B
unit.
CODE
C
TYPES
All
C elements are unique
and
non-interchangeable
within
and
between frame sizes. This is
accomplished by the rejec-
tion hardware
system of Fig.
14.
Variously
positioned
inter-
ference
pins
on the
rollout
tracks cooperate with notched
brackets
fastened to the
breaker's side
plates.
When
inser-
tion of the wrong
breaker is attempted, the
pins
and notches
do
not
align, thereby
preventing
the
breaker
f rom
seating into
the track
slots.
C
elements
employ the A-type drawout mechanism, but in
modified form
to
prevent
interchangeability with the
A units.
The
modification
spaces the breaker's right
side
mounting
pins
on shorter centers
(10-1
1/16) than those
on the
left
side
(11-718).
See
Fig. 10.
..E.TYPE'
REJECTION
Some
installations
require that breakers serving essential
circuits be
segregated
from identical models
deployed else-
where
in the
power
system. The
segregation
is
physical
and
is
accomplished
by supplemental rejection hardware
added
to the
breaker and
its
drawout compartment.
In this
publication
these
special category breakers are
designated as
"E-type".
They are interchangeable
as fol-
rows:
.
E-type
compartments
reject
standard breakers.
o
Standard compartments accept E-type breakers.
E-type rejection is an optional feature
available on B and
C
code breakers only.
On Code B breakers, the E-type rejection feature is
pro-
vided via
an extra hole in each bottom flange engaging corre-
sponding
pins
added to the drawout tray.
See
Fig. 15.
On Code C breakers,
E-type
rejection is achieved
by
notching
the breaker's
right
side
plate
to clear a special
rejection
pin
added to the right
slide
rail.
See
Fig. 16.
All
E-type
breakers have the
suffix
letter
E added to the
middle
digits
of
their
designation as
shown by
the following
example:
AKR-4BE-75.
16
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