Siemens GM-SG

Circuit
Breaker Positions
Mechanism
Operated
Cell
Switch
(
MOC
)
This switch is
operated
by
a
roller
on
the circuit breaker
.
The
circuit breaker
engages
the
MOC
auxiliary
switch
only
in
the
CONNECT
(
operating
)
position
unless
an
optional
TEST
position pickup
is
specified
in
the
contract
.
If
a
TEST
position pickup
is included
,
the circuit breaker
will
engage
the
auxiliary
switch
in
both
positions
.
The
MOC
switch
and
operating linkage
is illustrated
in
the lower
portion
of
Figure
37
.
Up
to
24
stages
may
be
provided
.
Truck
Operated
Cell
Switch
(
TOC
)
This switch is
operated
by
an
extension
of
the
top
plate
at
the
right
top
corner
of
the circuit breaker
.
This
switch is
operated
only
as
the circuit breaker is moved
to
or
from
the
CONNECT
position
.
The
TOC
switch
is
shown
in
the
upper
portion
of
Figure
37
.
Up
to
12
stages
may
be
provided
.
Circuit
Breaker
Ground Connection
A
sliding
contact
multiple
finger
assembly
for
grounding
the
circuit
breaker
frame
is mounted underneath the
circuit breaker truck
frame
,
as
shown
in
Figure
36
.
This
assembly
engages
the
ground
bar mounted
in
the cell
and maintains
a
solid
ground
contact
with
a
continuous
wipe
through
all
positions
.
The
contact
is broken
(
or
disconnected
)
when the
circuit breaker
passes
the
DISCONNECT
position
while
being
removed
from
the
cell
.
Figure
37
.
MOC
and
TOC
Switches
(
MOC / TOC
Switch
Covet
Removed
for
Photo
)
De
-
Energizing
Control
Power
to
Circuit
Breaker
Locate
the control
power
disconnect device
associated
with
the
circuit
breaker
.
This
disconnect
(
typically
,
a
pullout
type
fuse
holder
)
is
normally
located
on
the
secondary
device
panel
inside the
secondary
compartment
.
Removal
of
the
fuse
holder
de
-
energizes
control
power
to
the
circuit
breaker
in
the
respective
switchgear
cell
.
In
some
switchgear
assemblies
,
a
molded
case
circuit breaker is
used
in
lieu
of
the
pullout
type
fuse
holder
.
Opening
this
circuit breaker
accomplishes
the
same
result
:
control
power
is disconnected
.
Shutter
Operation
Two
shutter
operating
levers
,
one on
each side
of
the
circuit breaker cell
,
are
driven down
by
the
engagement
of
the wheels
on
the circuit breaker
frame
.
This
opens
the shutters
as
the
circuit
breaker
is
moved into the
CONNECT
position
and allows the shutters
to
close when
the
circuit breaker is withdrawn
.
The shutters
are
fully
closed
with
the circuit breaker
in
the
TEST
position
.
Circuit
Breaker Installation and Removal
Type
GMSG
vacuum
circuit breakers
are
normally
shipped
installed
in
the
switchgear
cells
.
They
are
normally
shipped
with
their
primary
contacts
open
and the
closing springs discharged
.
Before
racking
of
a
circuit
breaker
or
performing
any
inspection
or
maintenance
,
verify
that the circuit breaker is
open
with
closing
springs
discharged
.
Refer
to
instruction
manual
E
50001
-
U
229
-
A
285
-
X
-
US
00
for information
on
installation
,
maintenance
,
and
handling
of
these
circuit
breakers
.
Spring
Discharge
Check
Perform
the
Spring
Discharge
Check
before
inserting
or
removing
the
circuit
breaker
from
the
switchgear
.
Refer
to
Figure
38
.
The
spring discharge
check consists
of
simply
performing
the
following
tasks
in
the order
given
.
This check
assures
that
both the
tripping
and
closing
springs
are
fully
discharged
.
39
Courtesy of NationalSwitchgear.com