Modes Of Operation - Discussion; Spring Charging Mode - Siemens SDV-4A Instruction Manual

Interrupter/Operator Description
Figure 11. Breaker Open - Closing Springs Discharged.

Modes Of Operation - Discussion

Some maintenance procedures are more easily understood
when the operating mechanism modes of operation are
described in detail. The next few paragraphs explain the
five modes or status conditions (charging, closing, trip-free,
opening and rapid auto reclosing) of the stored energy
operating mechanism.
Note: All discussion of modes of operation assumes that
the reader is viewing the operator from the front, or from
the left hand side.
Spring Charging Mode - Figures 11 and 12 show several
key components of the operator mechanism in positions
corresponding to the breaker open, with the closing springs
discharged (Figure 11) and charged (Figure 12). Figure 13
shows portions of the operator mechanism that manually
or electrically charge the closing springs. The drive cam
(20), the closing spring crank arms (Figure 15) and spring
condition indicator cam (18) are directly keyed to the main
cam shaft (3). The main cam shaft rotates counterclock-
wise. The closing springs are attached to the crank arms
and are extended during the charging cycle.
Figure 13 shows the ratchet wheel (15) which is free to ro-
tate about the main cam shaft (3). The ratchet wheel is
driven by either the charging motor or the manual charge
handle socket (52). When the springs are charged electri-
cally, the motor eccentric (100) introduces a rocking mo-
Figure 12. Breaker Open - Closing Springs Charged.
tion into the drive plate (13). As this plate rocks back and
forth, the upper pawl (24-1) (which is connected to the drive
plate) imparts counterclockwise rotation of the ratchet
wheel (15), one tooth at a time. The lower pawl (24-2) acts
as a holding pawl during electrical charging.
When the springs are charged manually, up and down
pumping action of the spring charging handle in the manual
charge handle socket (52) causes the pawl plate (11) to rock
back and forth through the movement of the manual charg-
ing link (48). The lower pawl (24-2) drives the ratchet plate
counterclockwise during manual charging, and the upper
pawl (24-1) becomes the holding device.
At the beginning of the charging cycle, ratchet pin (16) is at
the 12 o'clock position. The ratchet pin is connected to the
ratchet wheel. Upon being advanced by ratchet action to
the 6 o'clock position, this pin engages the drive arms (8)
which are keyed to the main cam shaft. Consequently,
counterclockwise rotation of the ratchet wheel causes the
ratchet pin to drive the main cam shaft counterclockwise.
When the ratchet pin reaches the 12 o'clock position, the
closing springs are fully charged. Driving pawl (24-1) is
disengaged, the spring condition indicator cam (18) has
rotated allowing the spring charged flag (132) to drop into
the lower (charged) position, which also operates the mo-
tor cutoff switch (LS1) and spring charged switch (LS2) (258)
(see Figures 14 and 19). The closing springs are restrained
fully charged by close hatchet (22) against close shaft (72).
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