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EMI SnifferTM Probe
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info (at)

Tel: (541) 745-3935
Fax: (541) 745-3923

6410 NW Sisters Pl.
Corvallis, OR 97330


Eddy currents cause the high frequency resistance of windings to increase dramatically as the conductor approaches a skin depth in thickness; the ac resistance can exceed the dc resistance by factor of 10 to 100 or more in transformers with multi-layer windings or inductors with a discrete air gap. Additional losses are caused by partial winding layers, incomplete winding overlap, and poor lead breakouts with foil conductors. Losses are also increased with non-sinusoidal currents of high harmonic content, due to the increased eddy current losses at the higher harmonic frequencies.

This seminar explores and debunks many common myths and misconceptions about "skin and proximity effects", including:

  • "Replacing solid conductors with 'Litz' or stranded wire (always) reduces high frequency resistance."
  • "Skin effect is the HF current distribution in an isolated conductor."
  • "Stranded and foil conductors reduce the HF resistance because they have more 'skin'."

Seminar topics include:

  • The true nature of skin effects
  • Various proximity effects; single conductor, multi-conductor, single layer winding, and multi-layer winding proximity effects
  • Calculation of losses in single and multi-layer windings
  • Losses with non-sinusoidal currents
  • Induced winding losses near core air gaps
  • Excess losses in non-ideal planar windings
  • Conductor options for minimization of losses
  • Winding constructions for minimizing losses
  • "Dual" windings for simultaneous minimization of ac and dc losses
  • Eddy current losses in Faraday shields
  • Measuring ac conductor resistance, and common errors

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Last updated Saturday, November 9, 2002. Website design and development by Josie Nutter.
Project management and additional development by Loren DeLaOsa.