skin_depth

# Differences

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 skin_depth [2019/06/03 18:30] skin_depth [2020/07/02 22:35] (current) 2017/01/30 15:18 stan_zurek -review2016/01/02 22:12 stan_zurek new math2015/10/21 14:41 stan_zurek done2015/10/20 14:46 stan_zurek created Line 1: Line 1: + ====== Skin depth ====== + |< 100% >| + | //[[user/Stan Zurek]], Skin depth, [[http://Encyclopedia-Magnetica.com|Encyclopedia-Magnetica.com]], {accessed @YEAR@-@MONTH@-@DAY@}// | + + {{page>insert/just photo}} + + **Skin depth** (often denoted by lower-case Greek letter delta **δ**) - such a depth of penetration of [[alternating current]] or [[electromagnetic field]], at which the amplitude is reduced to a value of 1/[[e (constant)|e]] (around 37%), as compared to the amplitude at the surface of the [[conductor]]. + + Skin depth is a function of frequency of current, as well as [[magnetic permeability]] and [[electric resistivity]] (or [[electric conductivity|conductivity]]) of the conductor in question. + + For good conductors (like most metals) the function can be defined as:[([[http://google.com/books?isbn=9780387948775|Nathan Ida, Joao Bastos, Electromagnetics and Calculations of Fields, Springer, 1997, ISBN 9780387948775, p. 232]])] + + |
$\delta = \sqrt{\frac{2 · \rho }{\omega · \mu_r · \mu_0}} = \frac{1}{\sqrt{\pi · f · \mu_r · \mu_0 · \sigma}}$
|  (m)  | + + where: //π// - mathematical constant, //f// - frequency (Hz), //μr// - [[relative permeability]] of the conductor, //μ0// - [[magnetic permeability of free space]] (H/m), //σ// - [[electric conductivity]] (S/m), //ρ// = 1///σ// - [[electric resistivity]] (Ω·m), //ω// = 2·//π·f// - [[pulsation frequency]] (rad/s). + + + Skin depth vs. frequency for some materials (red line denotes 50 Hz): + * dashed black (**Mn-Zn**) - [[magnetically soft ferrite]] [[3C90]] + * light grey (**Al**) - metallic [[aluminium]] + * orange (**Cu**) - metallic [[copper]] + * green (**steel 410**) - magnetic [[stainless steel]], grade 410 + * blue (**Fe-Si**) - [[grain-oriented electrical steel]] + * dark grey (**Fe-Ni**) - [[permalloy]] (80%Ni-20%Fe) + [[file/skin_depth_magnetica.png|{{skin_depth_magnetica.png}}]] + {{page>insert/by_SZ}} + + + + + ===== See also ===== + *[[skin effect]] + *[[Litz wire]] + + ===== References ===== + ~~REFNOTES~~ + + {{tag>Skin_depth Skin_effect Counter}}

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