What is full form of ACB?ACB means Air circuit breaker which will operate in the air means the arc quenching medium is atmospheric pressure. Because of better insulating properties of oil in many countries the air circuit breaker is replaced by oil circuit breaker.
Full form of ACB is Air circuit breaker and its importance is still preferable choice to use an Air circuit breaker up to 15KV. Because the oil circuit breaker may catch fire when used at 15V.
Plain Air Circuit Breaker
Plain air circuit breaker which is also called Cross-Blast Circuit Breaker. In this type , the circuit breaker is fitted along a chamber which is surrounded the contacts. This chamber is known as arc chute.
The arc chute is made of refractory material. The walls of arc chute inside are shaped in such a way that arc is not forced into close proximity. It will drive into the winding channel which is projected on an arc chute wall.
The arc chute will have a lot of small compartments and has many divisions which are metallic separated plates. Each of small compartments behaves as a mini arc chute and metallic separation plate behave like a arc splitter.
Because of all the arc voltages will be higher than the system voltage therefore the arc will split into a series of arcs. It is only preferable for low voltage application.
Air Blast Circuit Breaker
This type of CB is used for high voltage 245 KV, 420 KV and also even more.Air blast circuit breakers are of two types:
- Axial blast breaker
- Axial blast with sliding moving contact.
Application and Uses of Air Circuit Breaker
- It is used for plant protection,transformer capacitors , electrical machines and generators.
- It is used in Low as well as High Currents and voltage applications.
- It is also used in the Electricity sharing system and GND about 15Kv
SF6 Circuit Breaker
In this type of CB the current carrying contacts operate inside sulphur hexafluoride gas is known as an SF6 circuit breaker. SF6 gas has excellent insulating property and high electro-negativity. It has high affinity of absorbing free electron. when a free electron collides with the SF6 gas molecule , negative ion is formed ; it is absorbed by that gas molecule.
SF6 + e = SF6
SF6 + e = SF5- + F
The negative ions which are formed will be much heavier than a free electron. Therefore, overall mobility of the charged particle in the SF6 gas is much less then the other gases.. The conducting current through a gas is mainly due to mobility of charge particles. Therefore for heavier and less mobile charged particles in SF6 gas, required very high dielectric strength. SF6 has very good heat transfer property due to low gaseous viscosity. SF6 is 100 times more effective as a arc quenching medium than air circuit breaker. SF6 gas is used for both medium and high voltage electrical power system from 33KV to 800KV.
Types of SF6 Circuit Breaker
- Single interrupter SF6 CB which is applied up to 220
- Two interrupter SF6 CB which is applied up to 400
- Four interrupter SF6 CB which is applied up to 715V
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