Re: AC wire resistance with proximitry effects

["Tesla list" <tesla@xxxxxxxxxx>]

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

Hi Gerry,

Yes, by half power I mean 1/sqrt(2) or the method of dividing the 
bandwidth (fh-fl) by the center frequency.

I found a fundamental error, i.e., typo or often referred to as a 
"boo boo". I typed in F as 112.9 in my calcs, when I should have 
typed 112900. So, my Q prediction was incorrect as well as the error. 
I'll redo here for clarification (with the correct frequency this time).

First, regarding Ldc. Your right, it's not in the equation for Fraga, 
but it is used when predicting Q. Here is what I'm doing, at least at 
this time.

ESR = wL/Q
Q = wL/ESR
I am replacing ESR with Fraga's resistance because it is a combined R.

For my coil, Fraga is 360.33 ohms. L is Ldc at 131.4 mH (meas).

Q = (2*pi*112900)*.1314/360.33 = 259
That is the prediction.

The measurement was 282.25, so the error 8.24%.

I was curious if Les is would help or worsen the approximation (it's 
worse). But maybe only on the bare coil only. I can only assume that 
during Fraga's work, Wheeler and Medhurst were their basis for checks 
and balances and it's likely they played a significant role during 
development. That's all I'm saying.

The key with Fraga is that it "may" be useful. Your coils Q is 
predicted at 271 with this method (assuming I have the correct inputs 
for self res). With all the other methods which do not include an 
overall resistance, I don't see their usefulness.

Loaded coil Q's are much lower. I'll throw my 9 x 30 toroid on top 
and check that out.

Take care,
Bart



Tesla list wrote:

> Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
>
>
> Hi Bart,
>
> Were your "1/2 power" points at 0.707 * Vpeak??
>
> > Original poster: "Barton B. Anderson" <bartb@xxxxxxxxxxxxxxxx>
> >
> > I  then tuned generator to half power points (via low-z amp).
>
>
> > Oh, btw, I checked Les and Ces in the equations. It's worse and has 
> > twice the error. As Fraga, Terman, Gary, etc. all compare and base 
> > their equations from Medhurst, it actually makes sense that the 
> > least error would occur with Ldc and Cdc in their particular equations.
>
>
> I'm not sure what this means.  Could you elaborate on what you did 
> to "check Les and Ces in the equations"??
>
> Where does Fraga, Terman, and Gary use Ldc and Cdc in their 
> equations??  I might have missed this point.
>
> I just reread my post and it sure got corrupted.  I'll have to have 
> a "talking to" with my typing fingers.  What I meant to say was the 
> Fraga equation does NOT look at L and C directly but only looks at 
> frequency in the skin depth calculation.  So, if your Les and Ces 
> predict the same frequency as the The Medhurst C and Wheeler L, then 
> I would think the Fraga prediction would be unaffected.  Of course, 
> you dont need the Les or Ces since you have a very accurate 
> frequency prediction.
>
> Gerry R.
>
>
> > > > 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.