What is Difference Between ACB, VCB and SF6


What is Air Circuit Breaker?

Air Circuit Breaker (ACB) is an electrical device used to provide Overcurrent and short-circuit protection for electric circuits over 800 Amps to 10K Amps. These are usually used in low voltage applications below 450V. We can find these systems in Distribution Panels (below 450V). Here in this article, we will discuss the working of Air Circuit Breaker.

air circuit breaker

What is a Vacuum Circuit Breaker?

A vacuum circuit breaker is a kind of circuit breaker where the arc quenching takes place in a vacuum medium. The operation of switching on and closing of current carrying contacts and interrelated arc interruption takes place in a vacuum chamber in the breaker which is called a vacuum interrupter.

vacuum circuit breaker

what is Sf6 Circuit Breaker?

A circuit breaker in which SF6 under pressure gas is used to extinguish the arc is called SF6 circuit breaker. SF6 (sulphur hexafluoride) gas has excellent dielectric, arc quenching, chemical and other physical properties which have proved its superiority over other arc quenching mediums such as oil or air. The SF6 circuit breaker is mainly divided into three types

  • Non-puffer piston circuit breaker

  • Single- puffer piston circuit breaker.

  • Double-puffer piston circuit breaker.

sf6 circuit breaker

Difference Between ACB, VCB and SF6:


Air Circuit Breaker

Vacuum Circuit Breaker

Sf6 Circuit Breaker

Abbreviation of the Circuit Breaker

Air Circuit Breaker

Vacuum Circuit Breaker

Sulphur Hexa Fluoride Circuit Breaker

Voltage Application

LV voltage application upto 690 Volts 50Hz/60 Hz

MV (Medium Voltage) from 11kV up to 33 kV

High Voltage and EHV application above 11kV to 1010 Kv

Arc Quenching Medium



SF6 Gas

Working Principle

Air act as a good dielectric medium. Since moving and fixed contact are kept in open air with closed package. Whenever the circuit breaker opens, the arc will be quenched by air

Free electron cannot be formed in vacuum, Since the vacuum filled In between the male and female contact. Whenever the circuit breaker interrupts, the arc will be quenched by vacuum.

SF6 Gases are absorbed the free electron, which is developed by the electric arc. Basically
Sulphur hexafluoride (SF6) is an inert, heavy gas having good dielectric and arc extinguishing
properties. It has high die-electric strength and outstanding arc quenching characteristics.

Medium Pressure

In ACB, open air pressure is enough to quenching the arc

10^-2 to 10^-6 torr vacuum pressure is maintained in the vacuum camper

2 – 2.5 bar SF6 gas pressure to be maintained


ACB does not require any refilling process, Since open air is free of cost

Yes, In VCB, there is no chance of re-filling process, upon failure of vacuum we should replace the vacuum container. Therefore in VCB we do replacement

SF6 gas can be refilled upon decreasing in gas pressure. The process is just like filling air to your car tire.


Indoor application, ACB cannot be used in outside.

Indoor application

Mostly Outdoor application, sometime indoor application


Frequent maintenance to be done.

Very rare, once installed means VCB works like any think

Periodic maintenance to be done

Arc Chute

Arc chutes are used to reduce arc development. It separates the arc in to smaller part. ACB cannot be operate without arc chute

VCB  does not require arc chute

SF6 Circuit breaker do not need arc chute arrangement.

Arc Development


Less. Vacuum circuit breakers have minimal arcing (as there is nothing to ionize other than the contact material). The arc quenches when it is stretched a very small amount (less than 2–3 mm (0.079–0.118 in)).


Current Transformer

CT can be placed inside of the circuit breaker

CT cannot be placed inside of VCB

CT arrangement will be done outside only.

Rake in Rake out




Spring Charge Motor

More than 1600A ACB comes with the spring charge motor

In VCB always manufactured with Spring charge motor

SF6 comes with spring charge motor

protection Relays

Almost 90% of the sportive relays are placed inside of the ACB.

It needs external protective relay

It needs external protective relay


Feeder, MCC, PCC and all low voltage distribution

Starting of High voltage induction Motor

Used in HT PCC and Switch yard.

Rating of the circuit breaker

Form 630 A to 6300A

From 1250 to 4000A

630 A to 4000A (With different voltage level )

Cost (Rupees/Amps)

less. Typically A Siemens make ACB cost around 100 Rs/Amps

125 Rs/Amps

175 Rs/Amps





Short circuit Breaking Capacity

Very less

Very high



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