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4 5
units and all pole unit details , including
contacts
.
known
as
wedge and
fingers
.
The
contact
make and break details for
1200 amperes
are
the
same
for
4.16
KV and
13.8
KV
breakers
.
also the
same
for
4.16
KV and
13.8
KV
breakers
.
When the
breaker
has been
levered
beyond the
test
position
,
a flag
covers
the window
to prevent
insertion
of
the
maintenance handle
,
push
the flag
out
of
the
way to
insert the
handle
.
DON
'
T EVER ATTEMPT TO CLOSE
THE BREAKER BY HAND AGAINST A LIVE
CIRCUIT
.
PROPER
CLOSING
REQUIRES
MORE
SPEED AND POWER THAN CAN BE
SUPPLIED BY HAND POWER
.
They
are
of the general
type
Don
'
t attempt to
Those
for 2000 amperes
are
The
stationary main
current
carrying
contacts
,
shown below the arcing
contacts ,
are
made of zirconium copper , silver
plated
and with anti
-
weld main
current
carrying
inserts
.
The zirconium copper
acts as
its
own
spring and
no
other spring is required
.
In the
1200 ampere breaker there
are a
total
of 4
contact
members ,
each slotted
part
way , making a total of 8
contact
points
.
When
the maintenance
closing handle
is used
,
the control circuit
should be
entirely
disconnected
to
prevent accidental elec
-
trical operation
at
the
same
time
.
IF
THE BREAKER
IS
CLOSED AND
LATCHED
WITH
THE
MAINTENANCE
CLOSING HANDLE BE SURE
TO REMOVE
IT FROM THE SOCKET BEFORE TRIPPING
THE BREAKER
.
In the 2000 ampere breaker
the main
contacts
are
similar
but
somewhat
wider
,
and
have 2 slots in each member
,
making
a
total of 12
points
of
contact
.
For further
operating details
, see
BASIC
OPERATING
INSTRUCTIONS
.
The arcing
contacts are
the
same
for
all ratings of breakers
.
They also
are
made of zirconium copper but of heavier
material
with
silver
-
tungsten
arc
tips
.
For this
reason
they
are not
tightly bolted
to
the
contact
block but
can
pivot slightly
,
under spring
pressure
.
They
are
backed
up by
compression springs
.
A stop is in
the
center to
limit inward travel
.
POLE UNITS
The
pole units
, as
shown in Figs
.
15 and
16 for
4.16
KV and
13.8
KV respectively
,
are
complete sub
assemblies
.
The
porcelain
supports
contain the main studs and
contact
blocks permanently anchored in the por
-
celain
.
The
p o r c e l a i n
supports are
permanently anchored in the pole unit
base
casting
.
All
other
pole unit
members
are
bolted or
pinned
on
.
These
comprise
the movable and stationary
contacts
,
the
contact
lift rod
,
the disconnecting
contacts
and the
arc
chute hinge bracket
.
The pole unit is
fastened to the chassis
by 4 bolts through the pole unit base casting
.
When
the 3
poles
are
mounted
on the
breaker
,
they
are
tied together with a glass
polyester brace
as
shown
in Fig
.
14
.
In operation
,
the arcing
contacts
make
first
on
closing
and
break
last
on
opening
.
For best performance
it is important that
the
individual
contact movement
be about
the
same on
each
side of
the entering wedge
.
These
are set at
the
factory
.
Extensive
closing and opening
tests ,
interrupting
both
high and low
currents ,
show that the
contacts
will maintain
proper
adjustment
for
long
periods
.
CONTACTS
ARC CHUTES
Figures 15
and
16
show
respectively
4.16
and 13.8 KV 1200
and 2000
ampere
pole
Figures 2
a ,
2 b and 2
c
illustrate the general
appearance of the 50
-
DH
-
P 75
,
50
-
DH
-
P
250
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