Siemens 5-GMI-350 - Overhaul; Circuit Breaker Overhaul

Maintenance
&
Overhaul
Page
25
tion
of
the
closing
springs
and
that
the
circuit
breaker
contacts
are
Open
.
5
.
Press
the
green
Close
pushbutton
.
Nothing
should
hap
-
pen
.
The
manual
spring
check
should
demonstrate
smooth
operation
of
the
operating
mechanism
.
Dashpot
Assembly
Check
GMI
circuit
breakers
contain
the
pneumatic
dashpot
as
-
sembly
shown
in
Figure
47
.
The
internal
piston
of
the
dashpot
is
connected
to
the
jack
shaft
by
a
push
rod
linkage
.
While
performing
the
manual
spring
check
,
a
simple
test
of
the
dashpot
is
made
by
placing
a
cloth
near
the
venting
hole
of
the
dashpot
.
If
sharp
,
positive
puffs
of
air
exit
from
the
venting
hole
when
the
breaker
trips
,
the
condition
of
the
dashpot
and
its
internal
piston
rings
is
acceptable
.
Check
the
dashpot
mechanical
linkages
for
smooth
opera
-
tion
at
the
same
time
.
tion
of
acceptable
contact
condition
is
checked
by
the
visibility
of
the
erosion
mark
shown
in
Figure
46
.
The
contact
erosion
check
procedure
is
:
•
Be
sure
the
breaker
primary
contacts
are
Closed
.
•
Observe
the
erosion
mark
(
Figure
46
)
of
each
pole
.
When
this
mark
is
visible
,
contact
wear
is
within
acceptable
limits
.
Figure
46
.
Contact
Erosion
Check
Mark
.
A
WARNING
The
breaker
tripping
spring
is
charged
.
Observe
precautions
concerning
physical
contact
with
components
of
the
breaker
subjected
to
sudden
,
high
speed
move
-
ment
.
4
.
Press
the
red
Trip
pushbutton
after
completing
the
con
-
tact
erosion
check
.
Visually
verify
the
Discharge
condi
-
Figure
47
.
Dashpot
Assembly
.
Courtesy of NationalSwitchgear.com