Siemens vacuum circuit breaker 38-3AH3 38 kV - Manual (Page 18)

Vacuum interrupter/
operator
The OPEN/CLOSED indicator (58.0),
CHARGED/DISCHARGED indicator (55.0)
and the operations counter (59.0) are
located on the front of the mechanism
housing (60.0).
Circuit-breaker pole
Refer to Figure 14: Type 38-3AH3 vacuum
circuit breaker pole section on page 19.
The vacuum interrupter (30.0) is rigidly
connected to the upper terminal and pole
support (20.0) by its terminal bolt (31.2).
The lower part of the vacuum interrupter is
stabilized against lateral forces by a
centering ring (28.1) on the pole-support
(40.0). The external forces due to
switching operations and the contact
pressure are absorbed by the struts (28.0).
Figure 13: Operating mechanism controls and indicators
55.0
53.0 - Manual close button
54.0 - Manual open (trip) button
55.0 - CHARGED/DISCHARGED indicator
58.0 - OPEN/CLOSED indicator
59.0 - Operations counter
58.0
59.0
53.0
54.0
Current-path assembly
Refer to Figure 14: Type 38-3AH3 vacuum
circuit breaker pole section on page 19.
The current-path assembly consists of the
upper terminal and pole support (20.0),
the stationary contact (31.0) and the
moving contact (36.0), that is connected
with the lower terminal (29.0) by terminal
clamp (29.2) and a flexible shunt (29.1).
Vacuum interrupter
Refer to Figure 9: Vacuum interrupter
cutaway view on page 15. The moving-
contact (36.0) motion is aligned and
stabilized by guide bushing (35.0). The
metal bellows (34.0) follows the travel of
contact (36.0) and seals the vacuum
interrupter against the surrounding
atmosphere.
Switching operation
Refer to Figure 14: Type 38-3AH3 vacuum
circuit breaker pole section on page 19.
When a closing command is initiated, the
closing spring, that was previously charged
by hand or by the motor, actuates the
moving contact (36.0) through jack shaft
(63.0), lever (63.7), insulated coupler
(48.0) and lever (48.6).
The motion of the insulated coupler is
converted into the vertical movement of
the moving contact.
The moving-contact motion is controlled
by the guide link (48.9), that pivots on
support (40.0) and the eye bolt (36.3).
During closing, the tripping spring and the
contact-pressure springs (49.0) are
charged and latched by the pawl (64.1).
The closing spring is recharged
immediately after closing.
In the CLOSED state, the necessary contact
pressure is maintained by the contact-
pressure spring and the atmospheric
pressure. The contact-pressure spring
automatically compensates for contact
erosion, which is very small.
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