ABB AMVAC Technical Manual page 3

AMVAC. The circuit breaker.
Although many refinements have been made throughout the 80-90 year
history of the medium voltage circuit breaker, there have been only four
generations of circuit breaker design. Early circuit breakers were spring
charged units with separate close and trip springs. These units were used for
older air-magnetic breakers. The second generation used the same
mechanism modified for use with a vacuum bottle. The new generation of
circuit breakers, such as the ADVAC breaker with a torroidal spring, were
designed specifically for use with vacuum technology.
Each generation reflects the best technology available at the time of their
introduction, building on the strengths of previous designs, yet adding new
innovations, marking true turning points.
Although it is well established that vacuum interrupters are capable of more
than 10,000 operations, conventional stored energy circuit breakers seldom
operate beyond 10,000 operations without teardown, re-lubrication, and/or
replacement of parts. More than 100 parts are required to perform spring
charging, closing, anti-pumping and tripping functions. Conventional stored
energy breakers also place limitations on the types of control voltages
allowed. Vacuum interrupters were mounted in open moldings, making them
susceptible to dust, moisture, and corrosive atmospheres.
The AMVAC is truly the next generation in medium voltage vacuum
technology. With the AMVAC, ABB is the first to combine the unique
requirements of vacuum interrupter technology to a stored energy
mechanism designed to exploit these capabilities. Using a flux-shifting device
with integral permanent magnets, the AMVAC mechanism has just seven
moving parts. Having only an open/close actuator, an electronic controller,
and capacitors for energy storage, the AMVAC circuit breaker mechanism is
capable of 50,000 to 100,000 operations. Vacuum interrupters are embedded
in a proprietary epoxy material, achieving excellent dielectric and thermal
capabilities. Eliminating mechanism operated cell switches, the AMVAC
breaker packages all auxiliary control contacts on the circuit breaker. These
are just a few of the features that mark a departure from the conventional
stored energy breaker and introduce new capabilities and benefits for the
modern power systems.
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