5

In using a particular type of conductor for an antenna in AC frequencies between 3MHz and 30MHz (HF), it was suggested that magnetic hysteresis losses may be significant if the permeability of the conductor was high.

How do I calculate the hysteresis losses for a straight line inductor carrying an AC current?

Community
  • 1
Adam Davis
  • 20,339
  • 7
  • 59
  • 95
  • Note that there is a related question [here](http://electronics.stackexchange.com/questions/99001/how-significant-are-hysteresis-losses-in-iron-wires-with-rf-currents?rq=1), but it doesn't ask for, nor has it received, specific guidance on how one would solve the problem - it only asks if it is a problem in a specific case. This question will hopefully result in answers that tell us how to solve the problem given an arbitrary wire. – Adam Davis Feb 10 '14 at 21:01
  • OK I've answered that question - is this what a straight line inductor is? I'm fairly convinced that the main loss for this type of inductor would be eddy-current losses not H-loss. – Andy aka Feb 10 '14 at 21:12
  • That may be the case, however I'd still like to be able to calculate it. I used the term "straight line inductor" to simply indicate a wire, treated as an inductor given the AC current on it. – Adam Davis Feb 10 '14 at 21:30
  • As far as I'm aware you have to have manufacturer's numbers to calculate H-loss - hysterisis material constant is usually supplied by ferrite manufacturers. That's the first problem - obtaining a value for iron or steel. Then because H-loss will likely be dwarfed by eddy current loss in a solid conductor it may never be stated. H-los and E-loss both rise with frequency so they might be a little hard to indistinguish even if you managed some kind of test. I'd love to hear a decent answer on this BTW. – Andy aka Feb 10 '14 at 22:55
  • Andy is correct, if the hysteresis loss coefficients are not available for the material in question, there's no way to calculate the hysteresis loss. I've never seen them given for a good conductor, but they are often available for ferrite, powdered iron, silicon steel, etc. I agree that the losses will be WAY dominated by eddy currents, but you could get some hysteresis loss if for example the conductor runs along a channel made of some high permeability material. – John D Mar 03 '14 at 00:33
  • @JohnD *" if the hysteresis loss coefficients are not available for the material in question, there's no way to calculate the hysteresis loss."* How do manufacturers do it when they have a material? Is it all essentially empirical testing, there are no models that can be used to approach a solution with a novel material? – Adam Davis Mar 03 '14 at 01:50
  • I'm only familiar with magnetics used in power conversion applications. In my experience, it IS all empirical testing to find the coefficients in some form of the Steinmetz equation. I'm not aware of any method that lets you model this for a new material based solely on material characteristics and no empirical testing. – John D Mar 03 '14 at 05:08
  • And since the eddy currents swamp the hysteresis losses, measuring this empirically isn't trivial. Hmmm... – Adam Davis Mar 03 '14 at 15:17

1 Answers1

1

Summarising the comments above, hysteresis losses will decline as your frequency increase and are not typically associated with the conductor itself.

Skin depth will start to take effect as your frequency rises, effectively increasing your impedance. This does need to be considered, espescially if your are attempting to transfer reasonable amounts of power through the conductor/antenna.

Refer to wikipedia: http://en.wikipedia.org/wiki/Skin_effect

smashtastic
  • 3,336
  • 21
  • 31