horizontal dead center of the crank arms is reached, the
torque of the closing springs starts to rotate the crank inde-
pendently of the driving motor. However, the stop roller on
the closing cam quickly stops the movement of the crank at
only a few degrees over center, and holds it there by coming
against the spring release latch. This is the “spring charged”
position. The motor cut-off switch cam (7) operates the
switch (15) through a lever (13) at this time, and the motor
stops.
At the instant the springs snap over dead center, the lobes
of the drive plates raise the pawl lifters (27), and prevent
the oscillator pawl (28) from engaging the next tooth in the
ratchet wheel. Thus the oscillator is free and renders the
exact stopping point of the motor not critical.
When the spring release latch is moved below the level of
the stop roller, the close cam is free to rotate; and the two
closing springs rotate the crankshaft counterclockwise to
close the breaker contacts. They assume the position shown
in Figure 4-6b and the cam as shown in Figure 4-7c. During
rotation, the drive plates move away from the ratchet wheel
pin. The ratchet wheel does not rotate during the closing
operation, thus preventing excessive wear on the teeth and
pawls.
Power operated breakers are also equipped for emergency
hand charging of the closing springs (Figure 4-8). This opera-
tion is similar to that of the motor and oscillator except a
separate emergency charge pawl (33) is used to advance the
ratchet wheel (17) several teeth on each stroke of the charge
handle (34). This device (26) also pivots on the crank shaft.
4-2.2 Power Operation
Refer to Figure 4-9 for the basic schematic and connection
diagrams.
With the breaker open and springs discharged, the motor is
energized through the limit switch (LS) and the “b” contact.
The green indicating light (G) is controlled by a separate “b”
contact, and when lit indicates the breaker is open.
The motor runs and charges the closing springs. When the
springs are fully charged, the limit switch (LS) opens in the
motor circuit and closes in the spring release coil (SR) circuit.
When the close contact (CS-C) makes, the spring release
coil (SR) is energized through the normally closed “Y” con-
tact, the limit switch (LS), and the breaker “b” contacts. This
releases the latch holding the stop roller on the close cam.
The springs are released to close the breaker. When the
breaker closes, the “b” contact opens to cut off the spring
release coil (SR) and motor (MOT), and the limit switch (LS)
contacts reset.
If the close contact (CS-C) is maintained, the anti-pump
relay (Y) will be picked up by the current through the spring
release coil (SR), and will open its “Y” contact in the spring
release (SR) circuit. This allows only one close operation until
the close contact (CS-C) has been reset. The “Y” coil has a
very low drop-out voltage.
On some breakers a special closing circuit may be pro-
vided which permits the closing springs to be automatically
recharged immediately after the breaker is closed, instead
of only after the breaker is opened. This is accomplished by
separating the motor and limit switch from the “b” contact
so the motor operation is independent of the position of the
breaker contacts. This arrangement makes the breaker suit-
able for use with instantaneous reclosing relays or in special
operating sequences.
Standard control utilizes AC or DC control power. For 240
or 120 volt AC equipment, the control power can be taken
directly from the source through fuses. For 480 and 600 volt
AC operation, a suitable control power transformer is used.
The transformer is optional for 240 volt AC systems. DC
control voltages are 48, 125 or 250.
When the breaker closes, the “a” contact in the shunt trip
(SH-TR) coil circuit also closes to complete this trip circuit.
The red indicator lamp (R) supervises the shunt trip circuit
to show that it is in working order. It also indicates that the
breaker is closed.
When control power is turned on, any power operated
breaker in the TEST or CONNECTED positions with its
springs discharged will have its motor energized until the
closing springs are charged.
4-3 Closing Mechanism
The mechanism is of the general variety of mechanically
trip free mechanisms. This means that the breaker can be
opened or tripped free from the closing mechanism at any
point in its closing stroke. It also means that if the trip latch
is held in the “trip” position while the spring release latch is
released, the closing springs will make a trip-free operation
but the breaker contacts will not close or move appreciably
toward the closed position.
Based on this construction, the breaker close and trip linkage
can have four steady state conditions. The arrangements of
the basic close and trip linkage for these four conditions are
shown in Figure 4-7.
Effective July 2010
Instructional Book
IB694C694-03
35
eaton corporation
www.eaton.com
