Technical data

Manual controls and indicators
All circuit breaker manual controls and
indicators are conveniently located on
the front of the circuit breaker. Standard
features include manual close button,
manual trip button, open-close indicator,
stored-energy closing spring charge/
discharge indicator, manual spring-
charging access port and close operation
counter.
Common operator family
Since the entire type 38-3AH3 range of
ratings uses a common stored-energy
operating mechanism design, less
training of maintenance personnel is
required, and stocking of spare parts is
reduced. The operating mechanism is
essentially the same operator as used on
the Siemens type GMSG circuit breaker
for 5 kV-15 kV switchgear.
Front accessible operating mechanism
The type 38-3AH3 stored-energy operator
is located at the front of the circuit
breaker. The front cover can be easily
removed to expose the operator for
inspection and maintenance. This feature
eliminates the need to tilt or turn over
the circuit breaker for normal service.
Trip-free design
The operating mechanism conforms to
the trip-free requirements of ANSI/IEEE
standards. The mechanism design assures
that the tripping function prevails over
the closing operation.
Simple barriers
Outerphase and interphase barriers are of
very simple design and located on the
circuit breaker, allowing the cell to be
free of barriers, except the CT barrier
located in front of the shutters. The
barriers on the circuit breaker remove
quickly and easily for maintenance. Most
maintenance can be performed with the
barriers in place.
Vacuum interrupters
The type 38-3AH3 circuit breakers use the
Siemens family of vacuum interrupters,
proven in over 600,000 circuit breakers
produced since 1976. Axial magnetic-
field contacts are used to maintain the
arc in diffuse mode and minimize contact
erosion. The chrome-copper contact
material assures lower chopping currents
than with designs employing copper-
bismuth contacts.
Vacuum circuit breakers
16
1
2
3
4
5
6
7
8
1. Stationary current connection terminal
2. Ceramic insulator
3. Arc chamber
4. Chrome-copper contacts
5. Ceramic insulator
6. Stainless steel bellows
7. Moving contact stem
8. Mechanical coupling for operating
mechanism
Figure 19: Vacuum interrupter