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Electrical Riddle No.47 - AC and DC resistance
what is the relation ship between ac and dc resistances of a wire or coil?
Author : Sinnadurai Sripadmanaban - From: Srilankan
 
#1
Sun, January 30th, 2011 - 15:47
The difference between ac and dc resistance of coil wire is subjected to skin effects. Skin effect accounts for the fact that the ratio of effective alternating current resistance to direct current is greater than unity. The magnitude of this effect, at high frequency on conductivity, magnetic permeability, and inductance, is sufficient to require further evaluation of conductor size, during design. The skin depth is defined as the distance below the surface, where the current density has fallen to 1/ε or 37 percent of its value at the surface.



When selecting the wire for high frequency, select a wire where the relationship between the ac resistance and the dc resistance is 1. Using this approach, select the largest wire, operating at 100 kHz.



The wire size closest to this area of 0.00137 is AWG #26 with 0.00128 cm2.
 
Author : Hamid - From: Iran- Firouzabad in Fars
 
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