Understanding Core Loss Measurement

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SUMMARY

This discussion focuses on measuring core loss in RF transformers and inductors, specifically referencing a PhD thesis that provides a practical method for understanding these measurements. The main confusion arises from equation 3.1, where the distinction between capital Ipp and lower-case ipp is clarified as a typo; Ipp should be replaced with ipp. Additionally, the impact of duty cycle D on core loss is explained, noting that duty cycles deviating from 50% introduce higher harmonic amplitudes, which increase core loss.

PREREQUISITES
  • Understanding of RF transformer and inductor design
  • Familiarity with core loss concepts in magnetic materials
  • Knowledge of harmonic analysis in electrical circuits
  • Ability to interpret academic research papers, particularly in electrical engineering
NEXT STEPS
  • Review the PhD thesis on core loss measurement for detailed methodologies
  • Study the effects of duty cycle on core loss in magnetic components
  • Learn about harmonic distortion and its impact on transformer efficiency
  • Explore advanced topics in magnetizing inductance and its role in RF applications
USEFUL FOR

Electrical engineers, RF circuit designers, and researchers focusing on transformer efficiency and core loss measurements will benefit from this discussion.

reson8r
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Hello folks,

I'm looking for a way to measure core loss in RF transformers and inductors. I found a PhD thesis here:
https://vtechworks.lib.vt.edu/bitstream/handle/10919/19296/Mu_M_D_2013.pdf
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...

Gerrit
 
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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