# Re: AC coil resistance equation

```Hello James,

>
>
> -----Original Message-----
> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
> Date: Friday, August 28, 1998 7:21 AM
> Subject: Re: AC coil resistance equation
>
>
> >Original Poster: "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>

<snip>

> >> I used the measured figure for Q of one of my coils (300),back
> >> calculated to find Rac (136 Ohms) and then used that as a substitute
> >> for 3.2*Rdc in your equation. I guessed that d^2*fo should be divided
> >> by 124 before taking log base 10. I got an answer of 786 which is
> >> about 2* what it should be. I think your 3.2*Rdc figure doesn't take
> >> turn-turn proximity effect into account. I was impressed nonetheless.
> >
> >The coil is actually spacewound so the proximity effect probably
> >isn't that significant. What might well be is the former (thickwall
> >PVC drainpipe). I guess your formula might come close for an airwound
> >coil. I should test it on a thinwall PE coil sometime. Source
> >impedance was about 7 Ohms at the frequency of interest (146kHz).
> >
> >Malcolm
> >
> >
> >
> Find inductance at 146KHz, if Xl = 7 ohms

Unfortunately that was the internal impedance of the signal generator.
It was also resistive.

> 7/(2 pi) = 1.114
>
> 1.114/146KHz = 7.631E-6
>
>
> Find capacitor that is resonant at the frequency of 146KHz using a coil with
> an inductance of 7.631 uH.

Forgive me for saying this but this is a case of GIGO. The primary
had nothing to do with my measurements of resonator Q.

> 1/146KHz = 6.849E-6
>
> 6.849E-6/2 pi = 1.090E-6
>
> 1.090E-6 Squared = 1.188E-12
>
> 1.188E-12/7.631 uH = 0.1557 uF
>
> To find the current required to operate the primary at the maximum peak
> voltage.
>
> Vs/(.5 * Xl[primary's AC resistance at the given frequency.])
>
> Your circuit 3.5 ohms output impeadance 1000v supply/3.5 ohms = 285.7
> Amperes, or
> V*I = P in watts  285,700 watts.
>
> Double the frequecy, and half the power.

1000V supply?????   The primary of that coil runs from about 8kVpk
max.

Malcolm

```