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Topic Title: Circuit Breaker
Topic Summary: 3 pole and 4 pole circuit breaker difference
Created On: 22 May 2013 07:36 AM
Status: Read Only
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 22 May 2013 07:36 AM
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Avatar for Oluwamuyiwa.
Oluwamuyiwa

Posts: 4
Joined: 15 October 2012

kindly illustrate the difference between 3 pole circuit breakers with 4 pole
 29 May 2013 12:23 PM
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oneye

Posts: 162
Joined: 25 February 2008

It has an extra pole - but what are you looking for ??

Late break/early make or similar ?
 25 June 2013 04:20 PM
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poni

Posts: 4
Joined: 12 December 2008

3pole does 3 phase/lives/lines
4pole does 3phase+n 4lives/lines
 26 June 2013 08:11 AM
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Avatar for Oluwamuyiwa.
Oluwamuyiwa

Posts: 4
Joined: 15 October 2012

Thanks Poni & Oneye. What are the factors that influence the choice of 3 Pole or 4 Pole? Does it have anything to do with the earthing scheme?
 03 November 2013 04:56 PM
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davidburke

Posts: 7
Joined: 28 April 2010

Oluwamuyiwa,

It really does depend what your application is, whether you need a neutral or not? Maybe for testing purposes? If you do need a neutral, then you need to determine whether you wish to break it with your conductive phases (use a 4P CB) or run it through a solid removable link. Either way you need to look at ways of making sure there is not a neutral to earth potential (Un-e = InZn).

To answer your latest question, yes it can be derived from what earthing system is available to you. There are different types of earthing arrangements such as TN-C, TT, TN-S, TN-C-S, IT neutral not distributed, IT neutral distributed.

If you are unsure, refer to BS7671 17th Edition, there is a section which reads about the provision for disconnecting the neutral. (Regulation 537.2.1.7)

David
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