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Siemens 38-3AH3 38 kV Instruction Manual page 35

Vacuum circuit breaker
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Trip-free interlock
Figure 32: Circuit-breaker interlocks and
ground disconnect on page 33 shows the
devices providing the trip-free interlock
function. The purpose of the trip-free
interlock is to hold the circuit breaker
operating-mechanism mechanically and
electrically trip-free. The circuit breaker is
held trip-free during racking and whenever
the circuit breaker is between the TEST and
CONNECT positions within the switchgear
This interlock functions so that the circuit
breaker primary contacts can only be
closed when in the CONNECT position, in
the TEST position or out of the switchgear
Rating interlock
Figure 32: Circuit-breaker interlocks and
ground disconnect on page 33 shows the
rating-interlock interference plates
mounted on the circuit- breaker frame. The
circuit-breaker interference plates are
complemented by matching plates located
in the cubicle.
The interference plates (rating interlocks)
test the circuit-breaker voltage, continuous
current and interrupting and momentary
ratings and will not allow circuit breaker
insertion unless the circuit-breaker ratings
match or exceed the cell rating.
Vacuum interrupter/
Circuit-breaker frame
The frame of the type 38-3AH3 vacuum
circuit breaker contains several important
devices and features deserving of special
attention. These are the ground
disconnect, the four racking wheels and
the four handling wheels.
Ground disconnect
Figure 32: Circuit-breaker interlocks and
ground disconnect on page 33 shows the
ground disconnect contact mounted at the
bottom of the circuit breaker. The spring-
loaded fingers of the disconnect contact
engage the ground bar (refer to Figure 33:
Circuit-breaker compartment (MOC/TOC
switch cover removed for photo) on page
34) at the bottom of the switchgear
assembly. The ground bar is to the right of
the racking mechanism, shown at the
bottom center of the switchgear.
Circuit-breaker handling wheels
The type 38-3AH3 vacuum circuit breaker
is designed for easy movement into and
out of the metal-clad switchgear assembly.
A section of indoor or Shelter-Clad
switchgear does not require a transfer
truck or lifting truck for handling of the
circuit breaker when all circuit breakers are
located at floor level. Once the circuit
breaker is racked out of the switchgear, the
unit can be pulled using the handles on
the front of the circuit breaker. The circuit
breaker will roll on its bottom four wheels.
Hazardous voltage and high-speed moving parts.
Will cause death, serious injury and property damage.
Do not by-pass interlocks or otherwise make interlocks
inoperative. Interlocks must be in operation at all times.
Read this instruction manual. Know and understand correct
interlock function. Check interlock function prior to inserting a
circuit breaker into a switchgear cubicle.



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