Siemens vacuum circuit breaker 38-3AH3 38 kV - Manual (Page 32)

Vacuum interrupter/
operator
When this happens, the latch (25.0) loses
its support and releases the striker pin
(23.0), that is forced out by the spring
(31.0).
On the undervoltage release 3AX1103, the
latch (25.0) is held by the locking pin
(21.0) as long as the armature (9.0) is
attracted (energized) (refer to Figure 21:
Operator sequential operation diagram on
page 28). If the circuit of the magnet coil
(7.0) is interrupted, the armature (9.0)
drops off, thus causing the latch (25) to
lose its support and release the striker pin
(23).
Following every tripping operation, the
striker pin (23.0) must be reset to its
normal position by loading the spring (31).
This takes place automatically via the
operating mechanism of the circuit
breaker.
Since the striker pin of the undervoltage
release 3AX1103 is latched only when the
armature is attracted, this trip is provided
with a screw (29.0) (refer to Figure 25:
Undervoltage lock/operate selection on
page 31).
This screw is provided to allow locking the
striker pin (23.0) in the normal position for
adjusting purposes or for carrying out trial
operations during circuit breaker servicing.
Position A (locked) disables the
undervoltage release. Position B is the
normal (operating) position.
Capacitor-trip device
The capacitor-trip device is an auxiliary
tripping option providing a short-term
means of storing adequate electrical
energy to ensure circuit breaker tripping.
This device is applied in circuit breaker
installations lacking independent auxiliary-
control power or a station battery. In such
installations, control power is usually
derived from the primary source. In the
event of a primary-source fault, or
disturbance with resulting reduction of the
primary-source voltage, the capacitor-trip
device will provide short-term tripping
energy for circuit breaker opening due to
the protective relay operation.
Figure 27: Secondary disconnect on
the circuit breaker
Figure 28: Secondary disconnect
inside the switchgear
Figure 29: Auxiliary switch
The capacitor trip includes a rectifier to
convert the 120 or 240 Vac control voltage
to a dc voltage that is used to charge a
large capacitor to the peak of the
converted-voltage wave (refer to Figure
26: Capacitor trip device on page 31).
Shock absorber
A type 38-3AH3 vacuum circuit breaker is
equipped with a sealed, oil-filled, viscous
damper or shock absorber (61.8) (refer to
Figure 15: Stored-energy operating
mechanism on page 20). The purpose of
this shock absorber is to limit overtravel
and rebound of the vacuum interrupter
movable-contacts during the conclusion of
an opening operation. The shock-absorber
action affects only the end of an opening
operation.
Secondary disconnect
Signal and control power is delivered to
the internal circuits of the circuit breaker
by an arrangement of movable-contact
fingers (refer to Figure 27: Secondary
disconnect on the circuit breaker) mounted
on the top of the circuit breaker.
When the circuit breaker is racked into the
TEST or CONNECT position in the metal-
clad switchgear, these disconnect fingers
engage a mating-disconnect block on the
inside of the switchgear (refer to Figure
28: Secondary disconnect inside the
switchgear). These electrical connections
automatically disengage when the circuit
breaker is racked from the TEST to the
DISCONNECT position.
All of the control power necessary to
operate the circuit breaker is connected to
this disconnect block inside the
switchgear. The external trip- and close-
circuits and associated circuits are also
connected to the same disconnect block.
Auxiliary switch
Figure 29: Auxiliary switch shows the
circuit breaker mounted auxiliary switch.
This switch provides auxiliary contacts for
control of circuit breaker closing and
tripping functions. Contacts are available
for use in relaying and external logic
circuits. This switch is driven by linkages
connected to the jack shaft.
32