Circuit Breaker Design - CR4 Discussion Thread

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Muthuvel Power-User Join Date: Jun 2012 Posts: 115	Circuit Breaker Design 01/29/2013 3:55 AM
	Why the electrical designer choosing MCCB for the above 63A rating feeder instead of MCB and choosing ACB for the above 800A rating feeder instead of MCCB?
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#1 Re: Circuit breaker design 01/29/2013 3:56 AM
	At a guess, perhaps the wiring downstream of the MCCB is only sized for a 63A load? Without seeing the installation it is difficult to say much more. __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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PWSlack Guru Join Date: Jan 2007 Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on. Posts: 32175 Good Answers: 839	#2 Re: Circuit breaker design 01/29/2013 4:19 AM
	...except that MCCBs probably are unavailable for 800A breaking current capacity. __________________ "Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
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JohnDG Guru Join Date: May 2006 Location: Reading, Berkshire, UK. Going under cover. Posts: 9684 Good Answers: 468	#3 Re: Circuit Breaker Design 01/29/2013 7:00 AM
	MCBs (Miniature Circuit Breakers) and usually only available up to 63A, so above that, MCCBs (Moulded Case Circuit Breakers) or ACBs (Air Circuit Breakers) are used. MCCBs take less space, but ACBs are more cost-effective above about 630A. So it's a trade-off of cost, space and availability. __________________ "Love justice, you who rule the world" - Dante Alighieri
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kvsridhar Guru Join Date: Sep 2009 Location: Temporarily at Ashburn, VA Posts: 2744 Good Answers: 164	#4 Re: Circuit Breaker Design 01/29/2013 8:09 AM
	In addition to what others have said, MCB/MCCB/ACB usage is also guided by the need to discriminate upstream and downstream breakers. The subject is vast, and you can get some good knowedge from the web. One example here: Merlin Gerin CB discrimination __________________ Nothing worthwhile can ever be taught, it can only be learnt.
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JohnDG (1); kvsridhar (1); PWSlack (2)

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