Difference between ACB and VCB

A circuit breaker is an electrical switching device that can open or close an electric circuit either normally or in case of fault. Therefore, a circuit breaker is one of the major component of an electrical power system or wiring system.

A circuit breaker is usually equipped with a control mechanism which enable it to operate automatically in case of abnormal conditions in the circuit. Since the different electrical systems operate at different voltage and current levels. Therefore, according to system voltage and current, there are various types of circuit breakers available such as MCB (Miniature Circuit Breaker), ACB (Air Circuit Breaker), OCB (Oil Circuit Breaker), VCB (Vacuum Circuit Breaker), SF6 circuit breaker, etc.

Read through this article to learn the differences between air circuit breaker and vacuum circuit breaker. But, before going into the differences, let's get a basic overview of both air circuit breaker (ACB) and vacuum circuit breaker (VCB).

What is ACB?

ACB stands for Air Circuit Breaker. The type of the circuit breaker in which air is used as the arc quenching medium is known as air circuit breaker or ACB.

An air circuit breaker (ACB) is generally used in low voltage applications, where the supply voltage is less than 450 volts. Therefore, the air circuit breakers are widely used in the distribution panels.

The air circuit breakers are suitable to provide short-circuit protection and overcurrent protection to the electric circuits over 600 amperes to 10 kilo-amperes. The primary advantages of the air circuit breakers are high performance, long life and easy to install.

What is VCB?

VCB stands for Vacuum Circuit Breaker. A vacuum circuit breaker (VCB) is the type of circuit breaker which uses vacuum between the electrodes as the arc quenching medium.

The vacuum circuit breakers are mainly used in medium voltage applications, where the supply voltage ranges from 11 kV to 33 kV. In the VCB, the contacts of the circuit breaker are enclosed in a completely sealed vacuum cylinder. When the contacts are separated due to vacuum between the contacts, no arc is produced.

The major advantages of a vacuum circuit breaker are no emission of gas in atmosphere, little maintenance required, no danger of fire, longer life, silent operation, etc. However, these are comparatively costlier than ACB.

Difference between ACB and VCB

Both ACB and VCB are the types of electrical switching devices designed to perform same function of switching and protection. However, they are different in many aspects from each other. The following table highlights the significant differences between ACB and VCB:

Basis of Difference ACB VCB Full Form ACB stands for Air Circuit Breaker. VCB stands for Vacuum Circuit Breaker. Definition An air circuit breaker is a type of circuit breaker that uses air as the arc quenching medium. A vacuum circuit breaker is a type of circuit breaker that uses vacuum as the air quenching medium. Supply voltage range ACB is suitable for low voltage range upto 450 volts. VCB is suitable for medium voltage range from 11 kV to 33 kV. Current ratings An ACB can be used to switch and protect the electric circuits of 600 A to 10 kA. A VCB can be used for the electric circuit of 600 A to 4 kA. Arc quenching medium Air acts as arc quenching medium in ACB. Vacuum acts as arc quenching medium in VCB. Pressure of arc quenching medium In ACB, the required pressure for arc quenching is maintained by open air. In VCB, the pressure of vacuum is about 10-2 torr to 10-6 torr. Development of arc The arc development is high in an ACB. The arc development in a VCB is low. Need of arc chute

Arc chute is a device that reduces the development of arc.

ACB necessarily requires an arc chute.

VCB does not require the arc chute. Maintenance ACB requires frequent maintenance. VCB rarely requires any maintenance. Current transformer installation In case of ACB, both indoor and outdoor installations of current transformer can be made. The current transformer is installed outside the VCB. Protection relay placement ACB involves internal placement of protection relays. In VCB, the protection relays are placed externally. Short circuit breaking capacity The short circuit breaking capacity of ACB is very less. VCB has extremely high short circuit breaking capacity. Installation It is very easy to install the air circuit breakers. The installation of vacuum circuit breakers is comparatively difficult. Cost ACB is relatively less expensive. The cost of VCB is comparatively more. Applications ACB is mostly used in low voltage applications such as in distribution panels, motor control centers (MCC) and power control centers (PCC), etc. VCBs are mostly used in medium voltage applications like for switching and protection of high voltage induction motors, secondary transmission substations, etc.

Conclusion

The primary function both ACB and VCB is the same, i.e., switching and protection of electrical circuits. The most significant difference between ACB and VCB is that an ACB uses air as the arc quenching medium, while a VCB uses vacuum as the arc quenching medium.