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# Total Harmonic Distortion of LLC primary current?

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#### cupoftea

Looking to calculate the percentage of total IRMS(pri) that is from the 100kHz fundamental?

....here attached is our primary current and the Fourier of it...it went 20dB peak at 100kHz so i want to calc the percentage at the ~100khz fundamental.

kindly received good formula for skin depth......r^2/[(r^2 - (r-d)^2)]
r is radius, and d is skin depth.....

...it shows that skin effect of the fundamental is pretty low.....but then there’s the need to calculate the skin effect of the harmonics….

I believe that the Fourier peak of 20dB (attached) means that the fundamental is approx 10Arms?
Since 20log(10) = 20
..now, the total irms(pri) = 11A...so that means the percentage of harmonics is very small here, would you agree?

#### Attachments

• Fourier of primary current.jpg
155.8 KB · Views: 50
• LLC primary current.jpg
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you can assume 11.5A rms for the fundamental and ignore all else ...

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