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Re: AC wire resistance with proximitry effects



Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi Gerry,

Ok, replacing the wire size recommendation is something to think about. I was in the mode of simply evaluating wire size with better information, but you may be right. Maybe Rac and Q would be better for the user. Well, that's assuming they understand the numbers in the first place. I'll have to ponder on this. Once we are gearing toward a finality on this post, I'll go back to the 8kHz coil and evaluate that again, because that situation identified a gross problem with the 5 sd situation.

Take care,
Bart

Tesla list wrote:

Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Bart,

This is very believable. The Medhurst correction was around 3 (iirc). My Q calculation without proximity effects was about 600 so that would make the "real" Q about 200. I will measure the Q soon for closure.
It sounds like having wire diameter >= 5sd isn't important for good Q (my coil has diam = 2.5 sd). Maybe we ought to replace the wire size recommendation in JavaTC with the Fraga resistance and Q predictions and leave it to the designer to choose the best tradeoffs.


Gerry R


Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Hi Gerry,

Fraga is looking "real". Have you checked your coils predictions with Fraga? I'm showing a Q of 207. My high turn 8.5" coil is showing a Q of 155. If memory serves, that's close to measurement. I'm trying to dig up my misc. Q measurements (scattered via emails, hand written notes, etc.). Anyway, could only get on the internet for a second, but wanted to mention that. I still need to do a lot of verification with the equation and values as I did it rather quickly. But, it certainly ballparked well.

Take care,
Bart

Tesla list wrote:

Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Bart,

After looking at the Fraga equation again, it does look and L and C directly. It uses the product of L and C by virtue of the frequency needed for skin depth. Your Les and Ces are the frequency determining equivalents that are suppose to be accurate to like 1%.
How accurate are Medhurst C and Wheeler L in predicting the correct frequency. I doubt there will be any significant difference especially since f gets sqrt'd which will cut the error in half.


Gerry R.

Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>

Also, with Fraga, Gary used Medhurst C and L. I wonder how it plays out with Ces and Les in place of Medhurst? As a matter of fact, I wonder how well a lumped effective L and C would work with all the equations? They probably won't change a great deal (but, I haven't looked at that).

Take care,
Bart