Disassemble-MCCB(moulded case circuit breaker)

Circuit breakers are electrical component to isolate the electricity.
There are several types of circuit breakers but, as i know ( you have to remember i am a just beginer with 5 year experience)
- Circuit breaker for Power distribution
- Circuit breaker for Motor protection


after remove front cover
vacancies near the switch are for the auxiliary switch for breaker on-off status and breaker trip
This is normal accessary for the breaker. (but not in the photo)


This is electronic card for fault detection such as
For Power distribution
- Protection against overload ( L : ABB breaker says )
- Protection against short-circuit with time delay ( S : ABB breaker says)
- Instantaneous protection against short-circuit ( I : ABB breaker says)
- Protection against earth fault ( G : ABB breaker says)
For Motor Protection
- Against overload with inverse time delay trip and trip characteristic according to an inverse time curve ( L : ABB breaker says)
- Against rotor block with delayed trip and trip characteristic with definite time ( R : ABB breaker says)
- Against short-circuit with Instantaneous trip ( I : ABB breaker says)
- Against phase current unbalance or loss of phase with delayed trip and trip characteristic with definite time ( U : ABB breaker says)
... There will be more than i know


you can see the black component which can measure the current to utilize the protection function.


you can see the component which is connected with 2 wire. this is trip shunt to activate the breaker trip this will actuated by the card signal.




main contactor part consist of moving part for on, off and stationary part for connect the power cable (or bus bar)
at the picture the black color mean there was a big breaking current



What ever the maker is, the basic operation of breaker is same but the structure and accessary compartment is different.