Technical data

g
Low current chopping characteristics
The chrome-copper contact material
used in Siemens vacuum interrupters
limits chopping currents to a
maximum of 5 A. This low value
prevents the build-up of unduly high
voltages and results in lower stress on
the insulation of load equipment.
g
No arc products vented to the
atmosphere
The sealed vacuum interrupter
prevents venting of arc products to the
atmosphere, and prevents any possible
contamination of the contacts by the
atmosphere. The metal vapor of the
arc quickly recondenses on the surface
of the contacts, although a small
amount may recondense on the arc
chamber wall or arc shield. The
recondensing metal vapor acts as a
“gutter” and recaptures more
molecules of certain gases that might
be liberated during vaporization. This
action tends to improve the vacuum in
the interrupter during its operating
life.
g
Non-toxic interruption by-products
The interruption process occurs
entirely within the sealed vacuum
interrupter. Even if a vacuum
interrupter is physically broken, the arc
products inside the vacuum interrupter
are not toxic. In contrast, gas-filled
interrupters produce toxic arc by-
products, requiring special precautions
in the event of a ruptured interrupter
housing.
g
Fewer components
The vacuum interrupter pole
construction is extremely simple and
consists of only seven moving parts
within the high-voltage area and only
two moving parts within the vacuum
interrupter chamber. This means
greater reliability and less maintenance
with vacuum interrupters as compared
to the greater number of parts in other
type interrupters, such as gas or oil.
g
Long vacuum interrupter life
The vacuum interrupter has a long
expected service life due to the careful
selection of components. The chrome-
copper contacts allow efficient
interruption with very little contact
erosion.
g
Immunity to environment
The capability of the vacuum
interrupter to interrupt current or to
withstand voltage is not directly
affected by conditions external to the
vacuum interrupter. High or low
altitudes, hot or cold temperatures,
moist or dry conditions or heavy dust
conditions do not affect the conditions
internal to the vacuum interrupter.
Conditions external to the vacuum
interrupter, however, could affect the
overall system operation and should
be considered in the specifications.
g
Virtually maintenance free
Vacuum interrupter maintenance
requires merely wiping dust or other
atmospheric elements from the
exterior, visually checking the contact
wear indicator and periodic dielectric
testing to confirm vacuum integrity.
g
Lower force requirements
The vacuum interrupter has a very low
moving mass compared to that found
in other interrupters. This allows a
smaller, more compact stored-energy
operator leading to long life and low
maintenance of the circuit breaker.
Vacuum circuit breakers
20
Figure 25: Side view of type 38-3AH3 circuit
breaker (outer phase barrier removed)