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ADE7758 Burden Resistor Value

Question asked by levi92 on Nov 26, 2013
Latest reply on Mar 7, 2014 by dlath

Hi, I'm using an ADE7758 IC for my project. I'm facing a problem of choosing the burden resistor for my current transformer:

 

My CT is having the specification as below:

http://my.element14.com/hobut/ctscm40100-5/transformer-current-100-5a/dp/1373199?Ntt=1373199

CT.JPG

From the AN-639 APPLICATION NOTE, page 4, I found that:

fq.JPG

 

So I do the same calculation as diagram below:

calculation.JPG

Please check whether my CTRN is correct? because I can't find it in the CT datasheet.

so now I got the burden resistor of 17.68mΩ. Is my calculation correct? If wrong, please guide me.

 

If yes, I found out that the Rb in circuit in ADE7758 Datasheet(Figure 34) is slightly different with the Rb in AN-639 Application note(Figure 2).

So I would replace the Rb of ADE7758 Datasheet Circuit with 2 units of Rb connection(Center-Tapped) in circuit of AN-639 Application note while remaining the 1kΩ resistor and 33nF cap?

ade.JPGcenter.JPG

Or by referring to the CT circuit in Figure 34, the Rb should have Vrb of 500mVpeak (Full Scale) to be send into the IAP-IAN channel when the CT(100/5A) output is maximum of 5A. Hence,

 

Vrb=500mVpeak=353.55mVrms

Irb=5A

so Rb= 0.07Ohm

 

am I correct?

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