Siemens GMI Series

Interrupter
/
Operator
Description
Vacuum
Interrupters
and
Primary
Disconnects
The
operating
principle
of
the
GMI
vacuum
interrupter
is
simple
.
Figure
11
is
a
cutaway
view
of
a
typical
vacuum
interrupter
.
The
entire
assembly
is
sealed
after
a
vacuum
is
established
.
The
interrupter
stationary
contact
is
connected
to
the
upper
disconnect
stud
of
the
circuit
breaker
.
The
inter
-
rupter
movable
contact
is
connected
to
the
lower
disconnect
stud
and
driving
mechanism
of
the
circuit
breaker
.
The
metal
bellows
assembly
provides
a
secure
seal
around
the
movable
contact
,
preventing
loss
of
vacuum
while
permitting
vertical
motion
of
the
movable
contact
.
Introduction
The
Type
GMI
vacuum
circuit
breaker
is
of
drawout
construc
-
tion
designed
for
use
in
medium
voltage
,
metal
-
clad
switch
-
gear
.
The
GMI
circuit
breaker
conforms
to
the
requirements
of
ANSI
standards
C
37.20
.
2
,
C
37.04
,
C
37.06
,
C
37.09
and
C
37.010
.
GMI
circuit
breakers
consist
of
three
vacuum
interrupters
,
a
stored
energy
operating
mechanism
,
necessary
electrical
controls
and
interlock
devices
,
disconnect
devices
to
connect
the
breaker
to
both
primary
and
control
power
and
an
operator
housing
.
On
some
circuit
breaker
ratings
insulating
barriers
are
located
between
the
vacuum
interrupters
or
along
the
sides
.
This
section
describes
the
operation
of
each
major
subassem
-
bly
as
an
aid
in
the
operation
,
installation
,
maintenance
and
repair
of
the
GMI
vacuum
circuit
breaker
.
FIXED
CONTACT
CURRENT
CONNECTION
7
7
g
'
A
7
g
CERAMIC
INSULATOR
g
'
4
7
/
7
g
A
7
%
'
A
A
g
A
l
A
A
7
ARC
CHAMBER
A
2
%
A
A
%
A
7
p
7
'
n
%
ARC
SHIELD
r
%
\
w
\
\
rr
y
v
y
Vi
%
N
im
FIXED
CONTACT
m
%
MOVING
CONTACT
•
-
-
-
'
.
T
r
g
%
d
CERAMIC
INSULATOR
g
g
-
2
7
,
g
2
2
2
g
2
METAL
BELLOWS
g
i
_
r
7
,
g
g
a
?
GUIDE
—
MOVING
CONTACT
CURRENT
CONNECTION
mu
Figure
11
:
Cutaway
View
of
GMI
Vacuum
Interrupters
.
When
the
two
contacts
separate
an
arc
is
initiated
which
continues
conduction
up
to
the
following
current
zero
.
At
current
zero
,
the
arc
extinguishes
and
any
conductive
metal
vapor
which
has
been
created
by
and
supported
the
arc
condenses
on
the
contacts
and
on
the
surrounding
vapor
shield
.
Contact
materials
and
configuration
are
optimized
to
achieve
arc
motion
and
to
minimize
switching
disturbances
.
Figure
10
:
Front
View
of
GMI
Breaker
.
8
Courtesy of NationalSwitchgear.com