stranded wire as opposed to solid

[deepthreat]

If I remember my electrical apprenticeship classes correctly, electrons flow upon the surface area of a wire and not through the core. With that in mind a stranded wire should conduct current more efficiently as there is more surface area on each strand and 19 strands in a stranded thhn conductor. Now to extend this line of thinking one step further...If I have a #12 solid conductor and a #14 stranded conductor, the stranded conductor should have more surface area with which to conduct current and therefore should have a higher ampacity than the #12. Now I would never take this line of thought into the field and apply it but I wonder where my thought is getting skewed. I would appreciate any guidance. Thanks in advance

 

[BigDon]

What your talking about is called the skin effect, and it is really negligible at 60Hz. In other words, the electrons are not bunching up very close to the surface at this frequency; they are spread out throughout most of the cross-section of the wire. Additionally, the stranded conductors in THHN are not electrically isolated from the adjacent conductors, so it acts as one conductor.

I've spooled power supply transformers that operated at 100kHz+ and it the skin effect is noticable at that frequency. (The skin effect increases as frequency increases) Sometimes, we'd have to use Litz wire, which is a lot like what you're talking about- many strands of individually insulated wires (with a thin coating).

 

[jim dungar]

...but I wonder where my thought is getting skewed. I would appreciate any guidance.

Stranded (7 or 19) wire is electrically identical to solid wire at 60Hz.

At 60Hz, skin effect does not begin to show up in tables until 266kcmil.

This is one of those "urban myths" that people like to spread about electricity (another is current taking the path of least resistance).