Technical data

Siemens type GM38 38 kV metal-clad
power switchgear assemblies with
horizontal drawout type 38-3AH3
vacuum circuit breakers take advantage
of the latest developments in vacuum
interrupter technology.
Voltage transformers (VTs) with their
associated drawout primary fuses can be
located in the cell above a 1,200 A or
2,000 A circuit breaker, allowing
significant space savings. Siemens
introduced this feature to the 38 kV
switchgear market with the launch of the
type GM38 design in 1993.
The equipment meets or exceeds the
latest standards of ANSI, IEEE and NEMA.
Type GM38 switchgear is designed for
use in industrial plants, commercial
buildings, electric utility systems,
cogeneration installations and other
electrical systems. It is commonly used
for protection and switching of
transformers, capacitors, buses,
distribution feeder lines and, in general,
for protection of any medium-voltage
power circuit.
Siemens experience gained in over 80
years of supplying metal-clad switchgear
in the U.S. has been captured in the type
GM38 design. The objective has been to
incorporate features designed to provide
safety, while simplifying operation,
maintenance and minimizing installation
cost.
The switchgear structure and the
drawout vacuum circuit breaker are an
integrated design, with dielectric,
thermal and interruption integrity built
directly into the basic design, not added
as an afterthought.
Siemens type 3AH3 operating
mechanism
The type 38-3AH3 circuit breaker uses
the proven Siemens type 3AH3 stored-
energy operating mechanism. This
operator is an evolution of the type 3A
family of operators first introduced in
1976. Over 60,000 type 3AH3 operating
mechanisms have been produced since
1998.
Faster interruption
Standard interrupting time is 5-cycles,
with an option available for 3-cycles.
Siemens vacuum interrupters
The vacuum interrupters used in the type
3AH3 circuit breaker are manufactured by
Siemens and have been proven in
thousands of installations since 1976.
The chrome-copper contact design used
in these vacuum interrupters assures low
chopping levels, eliminating the need for
surge protection on most circuits.
Front mounted operating mechanism
The simple type 3AH3 operating
mechanism makes maintenance and
inspection easy. The mechanism is
located on the front of the circuit breaker,
rather than underneath.
Maintenance intervals
If applied under ANSl “usual service”
conditions, maintenance of the circuit
breaker mechanism is only needed at five
year intervals.
Maintenance of the switchgear cubicle is
recommended at five year intervals and
primarily consists of cleaning insulation.
Floor rollout
No lift truck or dolly is needed to insert or
remove circuit breakers or drawout fuse
trucks in the lower cell of switchgear
located at floor level. For indoor
switchgear located on a raised
“housekeeping” pad or for outdoor non-
walk-in switchgear, a lift truck is required
to handle circuit breakers or drawout fuse
trucks.
Overview
4
Figure 1: Type 38-3AH3 circuit breaker
Front
Side (barrier removed)
Rear