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Continuous conduction mode PFC inductor does not need Litz winding?

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treez

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Hello,
Would you agree that the inductor of the PFC stage with the current shown below in it, does not need to be litz wound, since the CCM waveform has too-insignificant harmonics?
Ie, one strand of ECW wire should be enough?
 

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SunnySkyguy

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What is your requirement for THD? < 10%?
Is this over entire load and supply range?
Does SRF of inductor boost harmonics?
 
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treez

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thanks, I am speaking of losses due to skin effect, and that due to the low level of harmonics in the waveform, it obviously doesn't need litz winding.?

THD as per UK/USA regs
SRF doesn't boost harmonics in this case
 

Warpspeed

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Its difficult to give a definite verdict.
But you are quite right in that if the ratio of dc current to ac ripple current is large, as it can sometimes be in a continuous mode choke, then the effects of skin effect are much reduced.

But its a relative improvement, the frequencies and wire size still need some consideration.
Its really a judgement call. Back to back testing may be the only way to know for sure if litz offers a worthwhile reduction in copper loss.
 
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