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Siemens 38-3AH3 38 kV Instruction Manual page 21

Vacuum circuit breaker
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When a tripping command is given, the
energy stored in the tripping- and contact-
pressure springs is released by pawl (64.2).
The opening sequence is similar to the
closing sequence. The residual force of the
tripping spring arrests the moving contact
(36.0) in the OPEN (TRIPPED) position.
Operating mechanism
The operating mechanism is comprised of
the mechanical and electrical components
required to:
1. Charge the closing springs with
sufficient potential energy to close the
circuit breaker and to store opening
energy in the tripping- and contact-
pressure springs.
2. Means to initiate closing and tripping
3. Means of transmitting force and
motion to each of three poles.
4. Operate all of these functions
automatically through electrical-
charging motor, cutout switches, anti-
pump relay, release (close and trip)
solenoids and auxiliary switches.
5. Provide indication of the circuit breaker
status (OPEN/CLOSED), spring
condition (CHARGED/DISCHARGED) and
number of operations.
The essential parts of the operating
mechanism are shown in Figure 15:
Stored-energy operating mechanism on
page 20. The control and sequence of
operation of the mechanism is described in
the Operating mechanism section
diagrams in Figure 17-21 on pages 24
through 28.
Indirect releases (tripping coils)
The shunt releases (54.1) convert the
electrical-tripping pulse into mechanical
energy to release the trip latch and open
the circuit breaker.
The undervoltage release (optional) (54.2)
may be electrically actuated by a make or a
break contact.
Vacuum interrupter/
If a make contact is used, the coil is
shorted out, and a resistor must be used to
limit the current. The undervoltage-release
option mounts to the immediate right of
the trip coil (54.1).
Motor-operating mechanism
The spring-charging motor (50.4) is bolted
to the charging-mechanism (50.2) gear
box installed in the mechanism housing.
Neither the gear-box mechanism nor the
motor require any normal maintenance.
Auxiliary switch
The auxiliary switch (68.0) is actuated by
the jack shaft (63.0) and link (68.1).
Mode of operation
The operating mechanism is of the stored-
energy trip-free type. In other words, the
charging of the closing spring is not
automatically followed by the contacts
changing position, and the tripping
function prevails over the closing function
in accordance with ANSI/IEEE C37.04-
1999, clause 6.9.
When the stored-energy mechanism has
been charged, the circuit breaker can be
closed manually or electrically at any
desired time. The mechanical energy for
carrying out an "open-close-open"
sequence for auto-reclosing duty is stored
in the closing and tripping springs.
The details of the closing-spring charging
mechanism are shown in Figure 15:
Stored-energy operating mechanism on
page 20. The charging shaft is supported
in the charging mechanism (50.2), but is
not coupled mechanically 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 the cam disc (62.3), thus causing the
charging shaft to follow. The crank (62.2)
charges the closing spring (62.0).



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