Current transformer self-capacitance Re: Re: [TCML] Measuring secondary current

[Andreas Hahn <andreas.hahn@xxxxxxxxxxx>]

For future reference, the self-capacitance of a current transformer 
secondary 
isn't possible to measure using an LCR meter (I got 7uF), but this page 
(http://www.g3ynh.info/zdocs/magnetics/appendix/Toroid_selfC.html) 
suggests it can be estimated with the formula CL(pF) = 0.90 + 78.1 / N 
(for an FT50-61 core, but I can't imagine it varies that much).

Or just C=1pF for > 15 turns, C < 5pF for < 15 turns.



On Sun, 2 Sep 2012, Antonio Carlos M. de Queiroz wrote:

> On 1/9/2012 12:14, Andreas Hahn wrote:
> > Thanks. I was actually going off a post to TCML ages ago which recommended 
> > 300 turns on the toroid, evidently for a different purpose!
> >
> > Is there a reference for CT construction you can point me to? Certainly I 
> > can follow your directions approximately (say, 25 turns on the toroid, a 
> > 100nF capacitor, 470 ohm resistor), but I would be doing so without knowing 
> > how any of those values interact or affect the final measurement.
> I wrote this:
> http://www.coe.ufrj.br/~acmq/tesla/current.pdf
>
> Antonio Carlos M. de Queiroz
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