Vacuum Circuit Breaker VS Air Circuit Breaker:What’s The Difference?

What Is A Vacuum Circuit Breaker(VCB) ? A vacuum circuit breaker…

What Is A Vacuum Circuit Breaker(VCB) ?

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A vacuum circuit breaker is an electrical switch device that uses a vacuum to deactivate arcs when it opens and closes the current-carrying contacts. Its name implies that it utilizes a vacuum chamber (or interrupter) to extinguish electric arcs.

Vacuum circuit breakers have a steel arch chamber located in the center. They are symmetrically built and stacked in ceramic insulators. The vacuum interrupter maintains a vacuum pressure between 10 to 6 bar.

The type of material used to create the conductors that link two points can have an important effect on how efficient a vcb is. Leading companies consider Cr/Cr as the best material for producing these kinds of breakers.

The superior arc provides excellent insulating strength, making them ideal for medium and relatively high-voltage applications. However, they are not the finest choice for commercial purposes.

This is why vacuum circuit breakers are commonly recognized as high voltage indoor breakers. These breakers are ideal for systems that require an 11 to 33 kV voltage since they require very little upkeep.

What is an Air Circuit Breaker (ACB)?

An Air Circuit Breaker (ACB) is a type of circuit breaker used to provide protection of short circuit and overcurrent protection for electrical circuits. ACBs are commonly used in industrial and commercial settings, where they are often mounted in enclosures or switchgear.

ACBs work by using air to extinguish an arc generated during a fault condition. They can be used for both low-voltage and medium-voltage applications, and are available in many different types to suit various kinds of circuits.

An ACB provides reliable short circuit protection, as well as protection against overloads and other faults. By monitoring the electrical current passing through a circuit, the ACB triggers an arc extinguishing process when it detects a fault, thus providing effective short circuit protection for all types of electrical circuits.

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How does Vacuum Circuit Breaker Work?

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A VCB works by using the vacuum to interrupt arcs when the current present in the circuit exceeds the normal value. The contacts of the vcb are made up of two contact surfaces which are separated by a small gap.

When an arc is created due to high current, this arc is interrupted by releasing a vapor which will not stay in the gap due to its low dielectric strength. This vapor helps to extinguish the arc and thus, provides an efficient means of arc interruption.

Vacuum Circuit Breakers come in various types and can be used for different types of circuits depending on their requirements. It is one of the most effective forms of circuit breakers as it can provide reliable protection from electrical hazards.

How Does an Air Circuit Breaker Work?

An air circuit breaker (ACB) works by breaking the circuit when an over current or short-circuit fault condition is detected.

ACBs are typically located at the main switchboard of a building, and operate on a simple principle: when an excessive amount of current passes through the circuit, it causes an electromagnetic force which opens the contacts of the circuit breaker, thus disabling the power supply and preventing further damage.

The ACB can then be reset manually after the fault has been cleared. An ACB is designed to be able to withstand short time over currents during normal operation and will automatically re-close after any fault has been cleared. This makes it ideal for protecting electrical equipment from damage due to overloads or short circuits.

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Difference Between Vacuum Circuit Breaker (VCB) and Air Circuit Breaker (ACB)

Vacuum circuit breakers and air circuit breakers both have important roles. However, they have many distinctions, which can be seen in the following:

Voltage Applications

Air circuit breakers are typically utilized for applications with a voltage lower than 690 volts, which are usually denoted as LT (low tension) uses. Conversely, vacuum circuit breakers are the preferred option for medium voltage applications with voltages up to 33 kV.

Medium Pressure

Open-air pressure is sufficient to quench the arc in air circuit breakers. On the other hand, VCBs must maintain a vacuum pressure ranging from 10-2 to 10-6 torr.

Arc Chute and Arc Development

In an air circuit breaker, arc chutes are employed to stop arc formation. It segments the arc into smaller components. An air circuit breaker wouldn’t work without one of these. High levels of arc development are seen in ACBs.

Conversely, vcbs do not necessitate an arc chute. Moreover, vacuum circuit breakers have reduced levels of arc production since there is nothing apart from contact material to be ionized.


Since the exterior atmosphere is gratuitous, ACB does not necessitate hand-operated refilling. Conversely, there is no method to refill the vacuum in a VCB automatically. If it ceases to operate, you must substitute the vacuum receptacle.

Working Principle

The moving and stationary contacts are kept open air in a sealed package in an air circuit breaker. Thus, the arc is quenched by air every time the circuit breaker opens. Air circuit breakers are easily ionized because it contains less air, and air acts as the dielectric medium.

However, vacuum acts as the arc quenching medium in a VCB. The ability of a vcb to break short circuits is pretty impressive since free electrons cannot exist in the presence of a vacuum.


Air circuit breakers are frequently utilized in the LT MCC, the secondary feeder circuit of the power transformer, and the LT PCC. They are ideal for indoor use; you cannot use them outside.

On the other hand, Vacuum circuit breakers are used to start motors with higher horsepower.

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