
F
14
the spring yoke. Due to erosion, the
gap
between moving
and
fixed
stem contacts increases. This requires more
motion to close the contacts and
less
is
available
for
wear
gap. Thus.
as
the contacts erode the wear
gap
goes
down. the difference being proportional to erosion.
The wear gap
is
set to .56 to .62 inches
at
the factory.
When
it goes down to
.31
inches
it
approximates .12
inches
or
erosion. There
is
a step on the spnng yoke
sur-
face.
When
the front
edge
of
the nut approximately
lines
up
with
Otis
step, the
gap
is
nearly
.31
and
it
is
time to
replace the vacuum interrupter.
ft
is very unlikely that
the interrupter
will
have
to
be
replaced due to erosion
of
coo
tacts. However, wear gaps should
be
recorded at
the time
of
mstallalion
to
make determination
of
the
need
for
replacement.
Note that the wear gap nut
is
not
an
adjustment
nut
and must not
be
tampered with.
5.2
MECHANISM
The spring-stored energy operating mechanism
is
mounted
in
U1e
front
of
the breaker.
lt
includes
all
the elements
for
stormg the energy, closing
and
tripping
of
the breaker.
manual and electrical controls. and interlocks.
Manual
controls are
all
in
the front and readily accessible. Porce-
lain
insulators
in
the rear are used to mount the vacuum
interrupter assemblies. Mechanical motion to close and
open the interrupter contacts is provided thru porcelain
operating rods connecting this mechanism pole shaft to
the
beU
cranks of the mterrupter assemblies.
The mechanism
is
mechanically trip
free.
The closing
springs
may
be
charged manually with the maintenance
tool or electrically thru the charging motor. The inter-
rupter
is
closed
by releasing the energy stored
in
the
closing springs either manually or electrically. The energy
released
by
the closing springs closes the contacts, charges
the contact loadmg springs, charges the reset spring and
overcomes the friction encountered during the closing
operation. The breaker may be opened manually
or
electrically with the energy stored
in
the contact loading
springs and reset spnng.
Fig.
12
shows the front
view
of
the stored energy
mechanism.
S.2.1
Operation
of
Stored Energy
Mechanism
The spring-stored energy mechanism stores the closing
energy by charging the closing springs and applies the
released energy
Lo
close the breaker, charge the
con
tact
1.B. 32-254-lB
loading spnngs
and
reset sprmg. The mechanism may rest
in
any one
of
the four positions shown
in
Fig.
14
as
follows:
a.
Breaker open, closing springs discharged
b. Breaker open, closingsprings charged
c. Breaker closed. closing springs discharged
d. Breaker closed, closing springs charged
Closing Springs Charging
Fig.
13
shows the schematic
views
or
the spring charging
parts
or
the stored energy mechanism.
The major component
of
the mechanism
is
a
cam
shaft
assembly which consists
of
a hex shaft to which are at-
tached two closing spring cranks (one on each end). the
ratchet wheel and the closing ca"!.
The ratchet wheel
is
actuated by a ratcheting mechanism
driven by an electric motor.
As
the ratchet wheel rotates,
the closing spring cranks
and
the closing
cam
rotate with
it.
The
closu1g
spring cranks
have
spring ends connected
to I
hem
which are
in
tum coupled
co
the closmg springs.
As
the cranks rotate, the closing springs get charged.
Vig
13a
and
13b
are
schematic
views
of
the spring
charging portions
of
the storedenergy mechanism. Fig. I
3a
iliows the springs charged,breakerclosed position. Fig. l3b
shows the springs discharged, breaker open position. Rota·
tion
of
the motor eccentric causes the driving plate and
motor ratchet lever to oscillate. The drive pawl, part
of
the rat.:het lever assembly. also oscillates rotating the
ratchet wheel counterclockwise.
As
the ratchet wheel
rotates. the spnng cranks
also
rotate pulling the spring
ends with them to charge the closing springs (one ex-
tension spring on each end
of
the
cam
shaft).
Closing Operation
When
the closing springs are completely charged. the
spring cranks
go
over center and the closing stop roller
comes against the spring release latch Fig. 13a. The
clos-
ing springs
are
now held
in
charged position. They can
be
released
to
close the breaker
by
moving the spring
release
latch out
of
the way.This
is
done manually or electrically
by depressing the spring release
lever
which turns the
spnng release
"D"
shaft thru the spring release wire.
The force
of
the closing springs rotates the cam shaft
thru springs cranks. The closing
cam
being attached to
the
cam
shaft
also
rotates causing the breaker to close.
Courtesy of NationalSwitchgear.com