Re: Terry filter alternates?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Black Moon" <black_moons@xxxxxxxxxxx>


> Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>
>
> Hi,
>
> At 05:26 PM 12/3/2004, you wrote:
> > "Hi Black Moon,
> >
> > I think you will roast those 10W resistors.  On my old 6" coil the 1K
> > 50W
> > resistors would get really hot at the 12/120 power level.
> >
> > David E Weiss"
> >
> >         0.12^2*1000 = 14.4 watts (IF I didn't slip a decimal point.)
> >
> > What was the real current in those resistors?  Can't be very far from
> > sinusoidal with all of the leakage reactance.
> >
> > Ed
>
>
> You are also discharging the filter caps each time the gap shorts.
>
> http://hot-streamer.com/TeslaCoils/MyPapers/modact/Image165.gif
>
> 300pF at 21kV 120BPS....
>
> E = 1/2 C V^2 x BPS = 29 watts!!
(0.0000000003/2) * (7500^2)
0.00000000015
Err, Except im not using 21kv, using 15kv, and they only will be charged to 
7.5kv each, hence we get: 300pf and about 1watt at 120BPS
not sure where your math went wrong there, even at 21kv its only 7.938watts 
at 120bps. + the 14.4 watts of his 120ma nst still not close to 29watts.
And im only operateing at 30ma, hence 0.9 watts disipated in the resistors.
Hence by the sound of it, for a 30ma 15kv coil, 5watt resistors could even 
do in a pinch (assumeing the voltage did'nt expload them, hence why id 
probley use 10 watt resistors, mabey 2 in series)


> So we now have 43.4 watts in the resistors.  At 100 watts, they have a 
> 300C temp rise.  At 43 watts, they are cooking at 155C  Darn toasty!!
>
> Problem is the normal full rated temp for the power resistors is stunning 
> 300C!!  So we massively over rate them to keep the temperatures sane.
> Originally I used much smaller resistors, but everyone whined that they 
> were getting supper hot.  So I upped the size of the resistors like 4X and 
> no more complaints ;-))
>
> Cheers,
>
>         Terry