Siemens GMI Series

Interrupter
/
Operator
Description
Page
8
«
Introduction
h
The
Type
GMI
vacuum
circuit
breaker
is
of
drawout
con
-
struction
designed
for
use
in
medium
voltage
,
Metal
-
Clad
switchgear
.
The
GMI
circuit
breaker
conforms
to
the
re
-
quirements
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
con
-
nect
the
breaker
to
both
primary
and
control
power
and
a
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
subas
-
sembly
as
an
aid
in
the
operation
,
installation
,
maintenance
and
repair
of
the
GMI
vacuum
circuit
breaker
.
I
Figure
11
.
Rear
View
of
GMI
Breaker
.
lished
.
The
interrupter
stationary
contact
is
connected
to
the
upper
disconnect
stud
of
the
circuit
breaker
.
The
interrupter
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
mov
-
able
contact
,
preventing
loss
of
vacuum
while
permitting
vertical
motion
of
the
movable
contact
.
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
ifTJ
fp
Figure
10
.
Front
View
of
GMI
Breaker
.
P
/
Vacuum
Interrupters
and
Primary
Disconnects
s
/
i
The
operating
principle
of
the
GMI
vacuum
interrupter
is
simple
.
Figure
12
is
a
cutaway
view
of
the
vacuum
interrup
-
ter
.
The
entire
assembly
is
sealed
after
a
vacuum
is
estab
-
Figure
12
.
Cutaway
View
of
GMI
Vacuum
Interrupter
.
Courtesy of NationalSwitchgear.com