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  1. reson8r

    Understanding Core Loss Measurement

    I guess that's what I get for skimming the material! Thanks, Electricpete. I'll read the paper more thoroughly.
  2. reson8r

    Improving an existing LED Driver

    You might consider putting a filter inductor in series with your LEDs. That would smooth the current through them and reduce flicker. If V is the voltage your PWM switches between (in volts), I is the current your LED string draws when on (in amps), and t is the time period of the PWM...
  3. reson8r

    0-10 volt dimmer

    This is not very helpful, but typically dimmers don't use rheostats -- it's terribly inefficient. They use some form of chopping the power supplied to the light, with a triac or pulse-width modulator. That way the control element is always fully on or off so it doesn't use any power. To...
  4. reson8r

    Understanding Core Loss Measurement

    Hi Darrell, Thanks for your careful explanation. It's not intuitive that core loss would depend on D (at least to my intuition), but I can see how splitting the problem into + and - V partitions could lead to it. I'll draw some waveforms and see if I can improve my intuition. The square wave...
  5. reson8r

    Understanding Core Loss Measurement

    Hello folks, I'm looking for a way to measure core loss in RF transformers & inductors. I ran across this PhD dissertation: https://vtechworks.lib.vt.edu/bitstream/handle/10919/19296/Mu_M_D_2013.pdf which looks thorough and practical, but I'm having trouble understanding some of it. I've...
  6. reson8r

    How to calculate inductor flux density?

    Yes, it all depends on what you're driving. I asserted that "changing N doesn't change E" because I was assuming E was the fixed source. In that case, changing N changes B instead. Thanks for your help & insight!
  7. reson8r

    How to calculate inductor flux density?

    I don't quite agree with this. Faraday's Law describes a relationship between voltage and flux; it doesn't decree which comes first. If you apply a voltage across an inductor a flux will result, and vice versa. Anyway, I ground through the algebra and satisfied myself that the two expressions...
  8. reson8r

    How to calculate inductor flux density?

    Well, I'll be darned! I set up a hypothetical inductor in MathCad and calculated B both ways, and it comes out the same when I vary E, N, or f. In this example I'm applying E across the inductor and calculating I, but it would work the other way around too. There is a slight numerical...
  9. reson8r

    How to calculate inductor flux density?

    Yes, I'm assuming sinusoidal E and I. I'm not sure I follow the rest of your first paragraph. E and I are the voltage and current in the inductor at a given frequency and operating condition, and calculating B from one or the other gives different results. H in the middle of a loop is...
  10. reson8r

    How to calculate inductor flux density?

    And more puzzlement: increasing turns count N reduces B in the voltage formula but increases it in the current formula!
  11. reson8r

    How to calculate inductor flux density?

    There are two ways to approach calculating B: by inductor voltage E or by current I. The voltage formula is B = E / (k * Ae * N * f) and the current formula involves calculating H = (N * I) / (path length) and determining B from H * mu or a material hysteresis curve. The problem is these often...

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