Eaton 36W-VAC25, Instructions For Installation, Operation And Maintenance

Page: 25 / 48

I.B. 3A74499B
Page 19
Effective 11/97
5-2.2 CHARGING
Figure 5-6 is a schematic view of the spring charging
parts of the stored energy mechanism.
The major component of the mechanism is a cam shaft
assembly which consists of a drive shaft to which are
attached two closing spring cranks (one on each end),
the closing cam, drive plates, and a free-wheeling ratch-
et wheel. The ratchet wheel is actuated by an oscillating
mechanism driven by the motor eccentric. As the ratchet
wheel rotates, it pushes the drive plates which in turn
rotate the closing spring cranks and the the closing cam
with it.
The closing spring cranks have spring ends connected
to them, which are in turn coupled to the closing springs.
As the cranks rotate, the closing springs are charged.
When the closing springs are completely charged, the
spring cranks go over dead center, and the closing stop
roller comes against the spring release latch. The clos-
ing springs are now held in the fully charged position.
Closing springs may also be charged manually. Insert
the maintenance tool in the manual charging socket
(Figure 4.1a). Move it up and down approximately 38
times until a clicking sound is heard, and the closing
springs charging indicator indicates "Charged". Any fur-
ther motion of the maintenance tool will result in free
wheeling of the ratchet wheel.
5-2.3 CLOSING OPERATION
Figure 5-5 shows the position of the closing cam and
tripping linkage. Note that in Figure 5-5a in which the
breaker is open and the closing springs are discharged,
the trip "D" shaft and the trip latch are in the unlatched
position as in Figure 5-5b.
The closing springs can be released to close the break-
er by moving the spring release latch out of the way.
This is done electrically or manually by depressing the
spring release lever, which turns the spring release latch
out of the way of the closing stop roller. The force of the
closing spring rotates the cam shaft through the spring
cranks. The closing cam, being attached to the cam
shaft, in turn rotates the pole shaft through the main link
to close the breaker.
In Figure 5-5c the linkage is shown with the breaker in
the closed position before the closing springs have been
recharged. Interference of the trip "D" shaft with the trip
latch prevents the linkage from collapsing, and the
breaker is held closed.
Figure 5-5d shows the breaker in the closed position
after the closing springs have been recharged. Note that
the spring charging rotates the closing cam by one half
turn. Since the cam surface in contact with the main link
roller is cylindrical in this region, the spring charging
operation does not affect the mechanism linkage.
Since the primary contacts are completely enclosed in
the vacuum interrupter and not adjustable in any way, a
"Slow Close" capability is not provided with W-VAC
breakers.
5-2.4 TRIPPING OPERATION
When the trip "D" shaft is turned either by the trip button
or trip coil, all links return to the original "open" condition
shown in (Figure 5-5a).
5-2.5 TRIP FREE OPERATION
When the manual trip button is held depressed, any
attempt to close the breaker results in the closing
springs discharging without any movement of the pole
shaft or vacuum interrupter stem.
5-3 CONTROL SCHEME
There are two basic control schemes for Type W-VAC
breakers, one for DC control and one for AC control
voltages or more than one tripping element, but the prin-
cipal mode of operation is as follows:
As soon as the secondary disconnects engage, the
spring charging motor automatically starts charging the
closing spring, provided control power is available.
When the springs are charged, the motor cut off LS1/bb
switch turns the motor off. The breaker may be closed
by making the control switch close (CS/c) contact.
Automatically upon closing of the breaker, the motor
starts charging the closing springs. The breaker may be
tripped any time by making the control switch (CS/T)
contacts.
Note the position switch (PS) contact in the spring
release circuit in the scheme. This contact remains
made while the breaker is being levered between the
TEST and CONNECTED positions. Consequently, it
prevents the breaker from closing automatically, even
though the control switch close contact may have been
made while the breaker is levered to the CONNECTED
position.