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ACB | Air Circuit Breaker Working Principle

Air Circuit Breaker (ACB) is a Electromechanical equipment. Air Circuit Breaker used as a switch for the protection of electric circuits from short circuits or over current. The ACB operates at atmospheric pressure in air. The device used in the switching mechanism and protection of the electrical system.

Air Circuit Breaker

Working principle of air circuit breaker

When a circuit malfunction occurs, the first main contacts of the Air Circuit Breaker separated and the current of the circuit transferred to another contact, known as the arching contact.

Recurring contacts cut off and the arc cut off from the contacts. The arc moved upward with the incidence of electromagnet impact. The arc runner allows the arc to travel with itself. With the movement of the arc runner allowed to move upward and the connection split in this way.

Arc formed when the ACB circuit switch to open and close. So electrical arc needs extinguished to prevent this. Different dielectric materials used such as oil or gases used and for air circuit breakers, Here atmospheric air used as the dielectric.

The arc chutes acts as a resistance to air arc. The air acts as an insulator and forces the arc to extinguish rapidly. During the cycle change, it prevents the arc from improving when the current reaches zero. For high voltage applications such as electrical substations, pressurized air used so that circuit breakers can be used in those high voltage applications. In high voltage applications, pressurized air as a dielectric used because it has a higher value of dielectric constant than atmospheric air.

ACB Charging Mechanism

Spring charging mechanism motor is an element required for remote operation, also known as electrically operated. The spring-charging motor automatically charges the spring mechanism to close the circuit breaker and also recharges the spring mechanism when the circuit breaker is in the ON position. The mechanism shown below can charged and operated by hand.

ACB Charging Mechanism


Air chute air blast circuit breaker

In air chute air blast circuit breakers, the main contacts usually made of copper and conduct current in a closed position. Air chute air blast circuit breakers have low contact resistance and it silver plated. Arcing contacts heat resistant solid and made of copper alloys.

ACB Application:

Air Circuit Breakers used to control power station auxiliaries and industrial plants. ACB provide protection to electrical plants such as industrial plants, transformers, capacitors, LV panels and generators.

  • Its used for the protection of industrial plants and electrical machines such as capacitors, generators, and transformers, etc. 
  • Mainly ACB used in plants where there at risk of fire or explosion.
  • They also used for controlling power station auxiliaries
  • Also used in Low/High Current and voltage applications
  • Also used in maintaining the switchgear and indoor medium voltage.

Drawback of Air-Break Circuit Breaker

Some of the drawbacks of ACB

  • One drawback of the arc chute theory its inefficiency at low currents where electromagnetic fields are weak. Or inefficiency at low current when the electromagnetic field is weak.
  • The arc chutes of breaker is not less efficient in its lengthening action at high currents. Instead the movement of the arc into the arc chute of breaker tends to become slower.

Aplication of ACB:

ACB used for the protection of industrial plants and electrical machinery such as capacitors, generators and transformers.

Air Circuit Breaker mainly used on plants that are prone to fire or explosion

They also used to control power station auxiliaries

ACB used in low / high current and voltage applications

Switch gear also used to maintain the indoor medium voltage.

Disadvantage of air circuit breaker

Some of the shortcomings of the ACB are:

Effect of low current when Ro electromagnetic field is weak.

Current the arc chute of the breaker not efficient during prolonged operation at high currents, instead of the arc movement to the arc chute of the breaker slowed down.

ACB Ratings:

Air Circuit Breaker come with different ratings because different circuits use different current and voltage ratings. However, the ACB's standard ratings range from 600 Amps to 1600 Amps. Similarly, another class of ACB is in the 2000 Amps to 5000 Amps rating. These are the current ratings of the ACB. The Voltage, physical ratings and the shape of the ACB vary from manufacturing company to another.

Above mentioned working principle and applications all about an Air Circuit Breaker (ACB). Hope that you have got a better understanding of this. please give your feedback by commenting in the comment section below.

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