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Anonymous Poster

CT ratio & burden

10/28/2009 1:28 AM

if i have protection CT with multi CT ratio (1000/500/1) with design Burden 15VA

is this burden same for all the ratio

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#1

Re: CT ratio & burden

10/29/2009 7:34 PM

I am not too sure as it has never come up (we don't use multi-tap CTs). I was interested myself in knowing the answer but a quick search of the internet produced no clear answer.

If the CT is rated at 15VA burden then it is probably 15VA when connected 1000:1. 500:1 will result in lower secondary winding resistance and therefore allow a theoretically higher burden, but I don't expect the turns ratio to burden relationship to be linear (ie- 500:1 ratio to allow a burden of 30VA).

http://en.wikipedia.org/wiki/Current_transformer

For safety reasons I would assume that 15VA is your burden limit even if you intend to use the lower turns ratio (500:1).

Alternatively you could test the CT or discuss directly with the CT manufacturer.

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#2

Re: CT ratio & burden

11/01/2009 6:15 AM

Yes! The burden will remain same as long as the secondary current is same.

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