ABB VD4 Medium voltage vacuum circuit breaker
General
The new VD4 are a synthesis of the renowned
technology in designing and constructing vacuum
interrupters embedded in resin poles, and of
excellency in design, engineering and production of
circuit-breakers.
The VD4 medium voltage circuit-breakers use vacuum
interrupters embedded in resin poles.
Embedding the interrupter in resin makes the circuit breaker poles particularly sturdy and protects the
interrupter against shocks, accumulation of dust and
humidity.
The vacuum interrupter houses the contacts and
makes up the interrupting chamber.
Current interruption in vacuum
The vacuum circuit-breaker does not require an
interrupting and insulating medium. In fact, the
interrupters do not contain ionizable material. In any
case, on separation of the contacts an electric arc is
generated made up exclusively of melted and
vaporized contact material.
The electric arc remains supported by the external
energy until the current is cancelled in the vicinity of
natural zero. At that instant, the rapid reduction in the
load density carried and the rapid condensation of the
metallic vapour, leads to extremely rapid recovery of
the dielectric characteristics. The vacuum interrupter
therefore recovers the insulating capacity and the
capacity to withstand the transient recovery voltage,
definitively extinguishing the arc.
Since high dielectric strength can be reached in the
vacuum, even with minimum distances, interruption
of the circuit is also guaranteed when separation of
the contacts takes place a few milliseconds before
passage of the current through natural zero.
The special geometry of the contacts and the material
used, as well as the limited duration and low voltage
of the arc, guarantee minimum contact wear and long
life. Furthermore, the vacuum prevents their oxidation
and contamination.

EL type operating mechanism
The low speed of the contacts, together with the
reduced run and low mass, limit the energy required
for the operation and therefore guarantee extremely
limited wear of the system. The circuit breaker
therefore only requires limited maintenance.
The VD4 circuit-breakers use a mechanical operating
mechanism, with stored energy and free trip. These
characteristics allow opening and closing operations
independent of the operator.
The operating mechanism is of simple conception and
use and can be customised with a wide range of
accessories which are easy and rapid to install. This
simplicity converts into greater reliability of the
apparatus.
The structure
The operating mechanism and the poles are fixed to a
metal frame which is also the support for the fixed
version of the circuit-breaker. The compact structure
ensures sturdiness and mechanical reliability.
Apart from the isolating contacts and the cord with
plug for connection of the auxiliary circuits, the with
drawable version is completed with the truck for
racking it into and out of the switchgear or enclosure
with the door closed.
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01
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01 Vacuum interrupter
embedded in resin pole
• Vacuum interruption technique
• Vacuum contacts protected against oxidation and
contamination
• Vacuum interrupter embedded in the resin poles
• Interrupter protected against shocks, dust and
humidity
• Sealed-for-life poles
• Operation under different climatic conditions
• Limited switching energy
• Stored energy operating mechanism with anti-
pumping device supplied as standard
• Simple customisation with a complete range of
accessories
• Fixed and withdrawable version
• Compact dimensions
• Sturdiness and reliability
• Limited maintenance
• Circuit-breaker racking in and racking out with door
closed
• Incorrect and hazardous operations are prevented
thanks to special locks in the operating mechanism
and in the truck
• High environmental compatibility
1 Upper terminal
2 Vacuum interrupter
3 Resin housing
4 Stem of moving contact
5 Lower terminal
6 Flexible connection
7 Tie-rod spring fork
8 Tie-rod
9 Pole fixing
10 Connection to operating mechanisrn
