Re: 3 Pole & 4Pole MCCB which one is suitable

Home Electrical Engineering Forum General Discussion 3 Pole & 4Pole MCCB which one is suitable Re: 3 Pole & 4Pole MCCB which one is suitable

Spir Georges GHALI

Abdul Basit Khan said:


i am a user, and i need to define difference between 3 pole & 4 pole MCCB for 200kVA transformer & 275kVA generator in main distribution panel, if we use common neutral, what is the advantages and disadvantages.



ABdul Basit Khan

Dear ;


The using of ” 3 Poles ” or ” 4 Poles ” MCCB either for transformers or generators, that means if the ” Neutral ” should be directly connected ” 3 poles ” or switched on & off with phases ” 4 Poles ” will be decided after knowing the ” Earthing System ” used in the project. So, if you know the Earthing System you can decide which MCCB should be used for your application.


Regarding the ” Earthing Systems “, we use as follow :

     – TT,  TN-S,  IT (with distributed neutral) : the ” Neutral ” should be switched on & off with phases.

     – IT (without distributed neutral ) : we don't need it as we haven't a neutral

     – TN-C : as the Protection line & the Neutral are combined ” PEN “, this line should be directly and all ways connected.