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11
IB-65020A
Equipment Description
The charging motor (Figure 6, i), located
on the bottom right of the base pan, is
assembled to the circuit breaker by a
bracket that is bolted to the base pan. The
charging motor drive shaft inserts into the
eccentric drive shaft. The eccentric drive
shaft is supported by needle roller bearings
in the mechanism frame side sheets and
transmits the motor torque to the left side
of the mechanism.
When the charging motor is energized, the
eccentric drive shaft rotates and causes
the pawl support arms to pivot about the
camshaft (Figure 7, p). The drive pawl
(Figure 7, m), which is supported by the
arms, engages with the ratchet wheel and
drives the ratchet wheel one tooth at a
time. To prevent backwards motion of the
ratchet wheel, a spring-loaded holding
pawl is used to latch the ratchet wheel after
each advance from the drive pawl.
To ensure correct synchronization of the
drive and holding pawl, the position of the
holding pawl support arms are adjusted by
the holding pawl adjusting eccentric
(Figure 7, f), located at the left front of
the mechanism. When the mechanism is
operated manually, the top pawl becomes
the drive pawl and the bottom pawl
becomes the holding pawl.
As the ratchet wheel (Figure 7, i) rotates,
projections from its side faces engage the
drive plates. The drive plates are attached
to the camshaft, and cause the camshaft
to rotate. Crank arms (Figure 7, h) are
attached to the ends of the camshaft.
Crank pins (Figure 7, g) are assembled to
the crank arms, which point outward. The
crank arms engage the bottom ends of
the connecting rods (Figure 6, e). The pins
that project from the spring yoke, which
straddles the main closing spring, engage
the top ends of the connecting rods. As the
camshaft rotates the connecting rods pull
the spring yoke downward, compressing
the main closing spring.
The ratchet wheel drives the camshaft so
that the connecting rods go down to their
lowest position, and then start to move
upward. At a certain point, the spring force
overcomes friction and resistance and start
to rotate the camshaft. At the same time,
the pawls are uncoupled from the ratchet
wheel by the pawl lift drive plate
(Figure 7, j), and the motor cutoff switch
is operated. The motor cutoff switch
(Figure 7, t), located to the right of the
mechanism, is operated by the spring
charge indicator and motor cutoff cam
(Figure 7, q). The spring charge indicator
(Figure 1, q) displays that the mechanism is
charged.
The camshaft (Figure 7, p) is restrained
by the close latch arm engaging against
the close latch shaft. The main closing
cam, located between the mechanism
side sheets, is in a position where the
fundamental linkage can move to the reset
position.
The close latch shaft, when released either
by the closing coil or the manual close
operator, allows the main closing spring to
pull the crank arms upward. As the crank
arm moves upward it rotates the main
closing cam and drives the fundamental
linkage into the closed position. This action
causes the main linkage to rotate the
jackshaft to drive the operating pushrod
(Figure 4) toward the current carrying side
of the circuit breaker.
