Circuit breakers are installed and used for safety purposes in both residential as well as commercial and industrial areas. In power distribution, we need circuit breakers at different levels. Depending on the current carrying capacity, breaking capacity and other functions, we select a suitable circuit breaker according to our needs i.e. VCB, ACB (Air Circuit Breaker), MCCB and then MCB , this is common hierarchy being followed in power distribution system.
A CB (Circuit breaker) is a device which:
Control (make or break) a circuit manually or by remote control under normal and fault conditions.
Break a circuit automatically under fault conditions (like over current, Short circuit, etc).
Air Circuit Breaker
- Operates in air (where air-blast as an arc quenching medium) at atmospheric pressure.
- It has completely replaced by oil circuit breaker.
- No chance of oil fire like in oil circuit breaker.
- Rated Current up to 10k A.
- Trip thresholds and delays are adjustable.
- Electronically and microprocessor controlled.
- It is used in large industrial plant for main power distribution.
MCBB stands for “Molded Case Circuit Breaker“.
Rated current in the range of 10-2500 amps.
Thermal operated for overload and & magnetic operation for instant trip in SC (short circuit conditions).
Interrupting rating can be around 10k – 200k amps.
Trip characteristics is adjustable.
Suitable for high power rating and high energy i.e. commercial and industrial use.
Generally, used where normal current is more than 100 Amps.
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