[TCML] Re: Spark gap Resistance

[Barton B. Anderson]

Hi Greg,

I took a day to digest what your stated. I take it that the 2700V drop 
was measured across the spark gap itself and not acorss the primary 
circuit? If so, that's a huge loss. I went to your site looking for the 
4200A primary, but it shows the improved primary specs. So, I ran 
numbers and calc'd 13.6 ohms of primary impedance which matches your 14 
ohm statement well enough. What your stating is that by increasing the 
primary impedance to 14 ohms from 5.3 ohms, your wall socket power draw 
was half of what it was. Better impedance match I guess.

That's an impressive improvement!

I calc'd primary Q pretty low on your current primary (about 37). I'm 
still trying to figure out why the idea of high Q primary's are assumed. 
I think the assumption is due to the large wire or ribbon surface area 
and low turns. Doesn't work out that way, but I can certainly understand 
why it would be assumed. Maybe not so important. The primary and 
secondary Q's in my little window of the universe are getting rather 
similar.

Thanks for the numbers.
Take care,
Bart

Greg Leyh wrote:
> Hi Bart,
>
> I think that 0.65ohm accurately reflected the gap losses, or very 
> nearly so, since the voltage and current waveforms were in phase, 
> except that the voltage waveform was somewhat distorted relative to 
> the sinusoidal current waveform.  Still, by eye I would estimate this 
> distortion was at no more than 10%.  At 4200A the peak gap voltage 
> drop was about 2700V.
>
> Given that the operating Zpri was 5.3ohm, one might imagine that this 
> system would nominally work, as it did, although with considerable gap 
> losses.  The design improvements made in 1998 [increasing Zpri to 
> 14ohm, larger toroid] actually increased the arc performance while 
> reducing the maximum wall-plug draw down to about 25kW.  The rotary 
> gap can now operate steady-state without significant heating, as the 
> peak currents are now only about 2500A.  GL
>
>
>
>> From: "Barton B. Anderson" <bartb at classictesla.com>
>> Subject: Re: [TCML] Re: Spark gap Resistance
>> To: Tesla Coil Mailing List <tesla at pupman.com>
>> Message-ID: <47576D54.1050304 at classictesla.com>
>> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>>
>> 0.65 ohms is significant! I have to assume that 0.65 was an averaged 
>> value? It is still relatively small and I don't think reflects the 
>> gap losses associated with spark gaps. I wonder if those gap losses 
>> included the primary losses as part of the mix?
>>
>> Take care,
>> Bart
>>
>> Lau, Gary wrote:
>>> > Actually, since power is I-squared * R, peak power in the gap is 
>>> 1316 MegaWatts, or 1.3GW.  But that's a peak value, for a very brief 
>>> interval - good for bragging rights, but little else.  The RMS 
>>> current value for the duration of the gap on-time is a small 
>>> fraction of the 4200A (sorry, no estimate, but <<4200A).  And when 
>>> you average that over a duty cycle (picking numbers out of the air) 
>>> of ~ 10usec/8msec or 0.125% that the gap is actually on, you'd 
>>> arrive at a more realistic figure for the amount of energy that's 
>>> actually dissipated in the gap.
>>> >
>>> > Regards, Gary Lau
>>> > MA, USA
>>> >
>
>
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