Answer / saju

normally the contacts of CB are closed,when a fault occurs
these contacs are pulled apart hence an arc will be formed,
this arc has to be quenched for successfull
operation.circuit breakers are classified in different
ways,one of the ways is according to the arc quenching
medium.in air circuit breaker the arc quenching medium is
air,and in vaccum circcuit breaker it is vaccum

Answer / t eswara rao

During the breaker opening operation an arc will be produced
in between moving contacts and fixed contacts. It require
any medium to produce an arc. If there is no medium, there
is no arc. No medium means it is empty or VACUUM. So this
technique is used for quenching the arc in the vacuum
circuit breakers. So it is very clear that in perfect
vacuum, there is no arc produced.

In Air Circuit Breaker, air is used as arc quenching medium.
it is very simple in construction and cost is also low where
as the Vacuum circuit breaker is very costly due to its its
complicated construction for maintaining the vacuum in the
vacuum chamber

Answer / sk.raffique

When two current carrying contacts are separated in a
vacuum module, an arc is drawn between them. An intensely
hot spot or sparks are created at the instant of contact
separation from which metal vapor shoot off, constituting
plasma. The amount of vapour in the plasma is proportional
to the rate of vapour emission from the electrodes, hence
to the arc current. With alternating current arc, the
current decreases during a portion of wave and tends to
zero. Thereby the rate of vapour emission tends to zero and
the amount of plasma tends to zero. Soon after natural
current zero, the remaining metal vapour condenses and the
dielectric strength builds up rapidly, and restriking of
arc is prevented.

This principle is used in vacuum circuit breakers

Answer / jobmon jacob

Vacuum is an excellent insulating medium. Arc is formed at the instant of contact separation from which metal vapour shoot off, constituting plasma. The cotact material are selected in such a way that the chopping current is very minimum. With alternating current arc, the current decreases during a portion of wave and tends to zero. . Soon after natural
current zero, the remaining metal vapour condenses and the
dielectric strength builds up rapidly, and restriking of
arc is prevented.A small portion of metal is exhausted during this process.This is used for Medium voltages.ACB is in low voltages.Here air is the quenching medium.

Answer / virendra joshi

Fundamental diffrence is the quenching medium at the time
of Making & breaking of contacts ( vaccum or air )

Answer / furqan ahmad

In Vacuum CB, vacuum is the arc quenching medium. Whenever contacts were separated an arc formed between the contacts becoz of high potential gradient. Formation of arc is due ionization of medium between the contacts, as in vacuum CB medium is vacuum hence it can not be ionized but the vapour formed due to hot spots at the contact leads to the formation of arc. After natural current zero this vapours get condensed and arc ultimately extinguished and restriking prevented.

Answer / shahid kureshi

VCb And ACb one type switch which function ON/OFF in helthy
condition and operated in abnormal condition.

Answer / siddharth

when fault occure contacts of C.B. open. At that time arc
produce between fixed and moving contact.

C.B. is required to extanguised that arc.

In vaccume C.B. contacts of C.B. placed in highly vacuumed
bottel (i.e there is on any gas or air). For continuty of
arc oxigen is required. There for arc will be vanished.

In air C.B. there is arc spliter to quanche and to
langthand the arc. Due to long length arc resistance
increased and there for flow of current. So that arc
extinguished.

Answer / vishal

High resistance ARC quenching principle. Vacuum for HIGH
Voltage wr as AIR for low Voltage.

Answer / nilkanth

Vaccum C.B. working principle is that Arc quenching medium
is air our vaccum when fault occur then C.B.works because
of arc making by vaccum

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