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Understanding Core Loss Measurement

  1. Nov 12, 2015 #1
    Hello folks,

    I'm looking for a way to measure core loss in RF transformers and inductors. I found a PhD thesis here:
    which looks like just the ticket, but I'm having trouble understanding key parts. I've tried contacting the author with no success.

    Chapter 3 introduces a good practical method, but I'm stumped at eqn 3.1 (pg 66).
    • Why does Pcore depend on capital Ipp and not lower-case ipp? Capital Ipp results from the magnetizing inductance (Lm in fig 3.1), but lower-case ipp is the current step due to core loss.
    • Why does Pcore depend on duty cycle D? Driving fig 3.1 with a rectangular wave would result in a rectangular voltage across Rcore, so the power loss in Rcore shouldn't depend on D at all.
    • Not only do I not understand why D is in there, I don't see how its use in eqn 3.1 is derived.
    In short, I pretty much don't get eqn 3.1 at all! If anyone can help, I would greatly appreciate it. Then perhaps eqn 3.2 will start making sense...

  2. jcsd
  3. Nov 17, 2015 #2
    Thanks for the post! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
  4. Nov 20, 2015 #3
    I've gotten to the bottom of this, with some help from elsewhere. There is indeed a typo in eqn 3.1 -- Ipp should be ipp. And page 23 of the paper does touch on core loss dependency on D. Duty cycles away from 50% contain higher harmonic amplitudes, which contribute to higher core loss. That makes sense!
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