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pgola4u
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Join Date: Jun 2011
Location: Haridwar (India)
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Circuit Breaker Rating

11/05/2011 4:43 PM

hi everbody, i m just look at MCB rating and found that the there is no any proper series or order between them like 6 A, 10 A, 13 A, 16 A, 20 A, 25 A, 32 A, 40 A, 50 A, 63 A, 80 A and 100A why these rating like this? why they are not in proper series?... is any specific reason for such type of rating.. plz guide... and thanks in advance

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Tornado
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#1

Re: Circuit breaker rating..

11/05/2011 4:56 PM

So what do you think would be a proper ordering? Arithmetic or geometric progression, or something else? 400 different sizes from 1 to 400 amps?

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pnaban
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#2

Re: Circuit Breaker Rating

11/06/2011 1:07 AM

These ratings may have some relationship with standard sizes of copper conductors used in power cables. for instance 63A for 16mm^2 wire and so on.

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electricalexpert65
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#3

Re: Circuit Breaker Rating

11/06/2011 8:45 AM

STANDARDISATION, I would say!
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pnaban
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#4
In reply to #3

Re: Circuit Breaker Rating

11/06/2011 9:30 AM

Yes.Standard sizes of protective devices should correspond to current ratings of standardised cable sizes,otherwise it is meaningless. Refer BS 7671 relationship between Iz,Ib,In in which the load current,cable size(current rating) and size of PD(current rating) are interrelated. Compare the rated current of standard size cables- 1,1.5,2.5,4,6,10,15, 25, 35mm^2 etc with that of rated current of PDs.

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pgola4u
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#6
In reply to #4

Re: Circuit Breaker Rating

11/06/2011 1:39 PM

thanks a lot sir...

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kvsridhar
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#5

Re: Circuit Breaker Rating

11/06/2011 10:45 AM

The ratings are generally as per Renard Series (#5 or #10). Please read this Wiki page : http://en.wikipedia.org/wiki/Preferred_number

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