Technical data

Type 38-3AH3 vacuum circuit breakers
Siemens type 38-3AH3 circuit breakers
are available in 31.5 kA through 40 kA
interrupting classes, or 1,500 MVA on
the older “constant MVA” rating basis.
Continuous current ratings include
1,200 A and 2,000 A self-cooled and
3,000 A forced-air cooled.
Maintenance features
The type 38-3AH3 circuit breakers
incorporate many features designed to
reduce and simplify maintenance,
including:
Virtually maintenance-free vacuum
interrupter
Five-year maintenance interval
Floor rollout
Front-mounted operator
Common operator family
Simple interphase and outerphase
barriers
“Universal” spare circuit breaker
concept
Non-sliding current transfer
Rugged secondary disconnects.
Five-year maintenance interval on
type 38-3AH3 circuit breaker
When applied under mild conditions
(ANSI “usual service” conditions),
maintenance is only needed at five-year
intervals on the circuit breaker. The
maintenance interval for the switchgear
cubicles is also five years.
Low maintenance requirements
The vacuum interrupter is a sealed unit,
so the only maintenance necessary is to
clean off any contaminants and to check
the vacuum integrity. The vacuum
interrupters can be disconnected from
the stored-energy mechanism quickly,
without tools, and vacuum integrity
inspected by hand; alternatively, a simple
high-potential test can be used.
Floor rollout
The circuit breakers are arranged to
rollout directly on the floor in front of the
switchgear, if the indoor switchgear is
not located on a “housekeeping” pad. No
adapter, hoist or lift truck is necessary for
circuit breakers located at floor level.
Mechanism operation
The mechanism is arranged to pre-store
closing energy in the closing springs. The
closing springs are selected so that they
provide sufficient energy not only to
close the circuit breaker safely into
maximum “close and latch” currents, but
also to pre-store the tripping energy
necessary to open the circuit breaker. The
closing springs can be manually charged
during maintenance or in emergency
conditions, but are normally charged
electrically automatically after each
closing operation.
Interlocks
The racking system prevents racking of a
closed circuit breaker and keeps the
circuit breaker trip-free during racking.
The racking mechanism can be padlocked
to prevent unauthorized operation.
Padlocks can also be applied to the
racking mechanism to maintain the
circuit breaker in the trip-free condition.
Stored-energy operator
The type 38-3AH3 circuit breaker utilizes
the Siemens type 3AH3 stored-energy
operator for long life, high reliability and
ease of maintenance. Parts used in the
manufacture of the circuit breaker are
precision tooled or produced on
numerically controlled equipment. The
circuit breaker design includes frequent
use of inherent alignment techniques.
Vacuum circuit breakers
15
Figure 18: Type 38-3AH3 circuit breaker
Front
Side (barrier removed)
Rear