Construction; Indirect Releases (Tripping Coils) (Figure 6); Motor Operating Mechanism (Figure 6); Auxiliary Switch (Figure 6) - Siemens 3AH Instructions, Installation, Operation, Maintenance

Interrupter/Operator Description

Construction

The essential parts of the operating mechanism are shown
in Figure 6. The control and sequence of operation of the
mechanism is described in Figure 7.

Indirect Releases (Tripping Coils) (Figure 6)

The shunt releases (54.1) convert the electrical tripping
pulse into mechanical energy to release the trip latch and
open the breaker. The undervoltage release may be elec-
trically actuated by a make or a break contact. If a make
contact is used, the coil is shorted out, and a resistor must
be used to limit the current. The undervoltage release op-
tion mounts to the immediate right of the trip coil (54.1).

Motor Operating Mechanism (Figure 6)

The spring charging motor (50.4) is bolted to the charging
mechanism (50.2) gear box installed in the mechanism
housing. Neither the charging mechanism nor the motor
require any maintenance.

Auxiliary Switch (Figure 6)

The auxiliary switch (68) is actuated by the jack shaft (63)
and link (68.1).

Mode of Operation

The operating mechanism is of the stored-energy trip free
type, i.e., the charging of the spring is not automatically
followed by the contacts changing position, and the clos-
ing function may be overridden by a trip command at any
time.
When the stored-energy mechanism has been charged,
the instant of operation can be chosen as desired.
The mechanical energy for carrying out an "open-close-
open" sequence for auto-reclosing duty is stored in the
closing and tripping springs.

Charging

The details of the closing spring charging mechanism are
shown in Figures 6. The charging shaft is supported in the
charging mechanism (50.2), but is not coupled mechani-
cally with the charging mechanism. Fitted to it are the
crank (62.2) at one end, and the cam (62.3), together with
lever (62.5), at the other.
When the charging mechanism is actuated by hand with a
hand crank or by a motor (50.4), the flange (50.3) turns
until the driver (50.3.1) locates in the cutaway part of cam
disc (62.3), thus causing the charging shaft to follow. The
crank (62.2) charges the closing spring (62). When this
has been fully charged, the crank actuates the linkage (55.1)
via control lever (55.2) for the "closing spring charged"
indicator (55), and actuates the limit switches (50.4.1) for
interrupting the motor supply. At the same time, the lever
(62.5) at the other end of the charging shaft is securely
locked by the latching pawl (62.5.2). When the closing
spring is being charged, cam disc (62.3) follows idly, i.e., it
is brought into position for closing.

Closing (See Figure 6)

If the breaker is to be closed locally, the closing spring is
released by pressing CLOSE button (53). In the case of
remote control, the spring release coil 52SRC (53.1) un-
latches the closing spring.
As the closing spring discharges, the charging shaft is
turned by crank (62.2). The cam disc (62.3) at the other
end of the charging shaft actuates the drive lever (62.6),
with the result that jack shaft (63) is turned by lever (63.5)
via the trip free coupling rod (62.8). At the same time, the
levers (63.1), (63.5), and (63.7) fixed on the jack shaft oper-
ate the three insulated couplers for the breaker poles. Le-
ver (63.7) changes the open-close indicator over to open.
Lever (63.5) charges the tripping spring (64) during clos-
ing, and the breaker is latched in the closed position by
lever (64.3) with pawl roller (64.3.1) and by pawl (64.2).
Lever (63.1) actuates the auxiliary switch through the link-
age (68.1).
The crank (62.2) on the charging shaft moves the linkage
(55.1) by acting on the control lever (55.2). The closing
spring charged indication is thus canceled and, the limit
switches (50.4) switch in the control supply to cause the
closing spring to recharge immediately.

Trip Free Operation (Figure 6)

The trip free coupling rod (62.8) permits the immediate
de-coupling of the drive lever (62.6) and the jack shaft (63)
to override closing action by trip command or by means
of the racking interlocks.
The trip free coupling rod (62.8) forms a link between the
drive lever (62.6) and the jack shaft (63). The rigidity of
this link depends upon a spring return latch carried within
the coupling rod. The latch pivots within the coupling rod
and is normally positioned to ensure the rigidity of the
coupling rod. Trip free coupling link (62.8.2) and trip free
coupling lever (62.8.3) cause the spring return latch posi-
tion to be dependent upon the normal tripping compo-
nents and the racking interlock. Thus, whenever a trip com-
mand is applied or the breaker is not in the fully CON-
NECT or TEST position, the trip free coupling rod is no
longer rigid, effectively decoupling the drive lever and jack
shaft. Under these conditions the vacuum interrupter con-
tacts cannot be closed.

Opening (Figure 6)

If the breaker is to be tripped locally, the tripping spring
(64) is released by pressing the trip button (54). In the
case of an electrical command being given, the shunt trip
coil 52T (54.1) unlatches the tripping spring (64).
The tripping spring turns the jack shaft (63) via lever (63.5);
the sequence being similar to that for closing.
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