Re: DC secondary components

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "rheidlebaugh by way of Terry Fritz <twftesla-at-qwest-dot-net>" <rheidlebaugh-at-zialink-dot-com>

Your speculation is correct: The current is very small. I measure it in p
amps not u amps. The current time laps can be long (days) or it can be in
u-sec. I use a space charge voltmeter to measure the voltage. This method
can measure the charge difference of the air in less than 25 cm height
changes. ( an average 120 V/100 ft of height change is normal background)
   Robert  H

> From: "Tesla list" <tesla-at-pupman-dot-com>
> Date: Fri, 15 Feb 2002 17:03:46 -0700
> To: tesla-at-pupman-dot-com
> Subject: Re: DC secondary components
> Resent-From: tesla-at-pupman-dot-com
> Resent-Date: Fri, 15 Feb 2002 17:09:50 -0700
> 
> Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <jimlux-at-earthlink-dot-net>
> 
> 
> 
>> The best you'll get is a small DC component to the base current
>> resulting from asymmetrical conduction (partial rectification) within
>> the topload discharge.
>> 
>> Can anyone remind me what polarity that will be?  I'd dearly like
>> to know if/how this DC base current relates to streamer length,
>> bang size, etc.  Does the current increase from bang to bang within
>> a burst?
>> 
>> 
>> There is no DC coupling between primary and secondary, so only the
>> AC components can get through.  Any DC component present in the
>> secondary must therefore be due to non-linearity of the secondary
>> load, or of the ground return circuit.
> 
> I should think that a spark is a pretty nonlinear phenomenon...
> Measurement of average DC current might be very interesting, and a very big
> measurement challenge in the presence of large AC currents and fields.
> 
> Corona discharge isn't a particularly high current phenomenon ( a few mA),
> and in the case of a TC, the duty cycle is very low (i.e. only when a
> "bang" is in progress).  Most of the spark theory says that the charge for
> a free air streamer moves back into the source as the spark collapses,
> leaving essentially neutral (net) air behind (it might be ionized, but
> there's an equal number of + and - ions).
> 
> Without giving it much thought, I would expect the DC average current to be
> in the microamps, with the peak (during a bang) perhaps in the milliamp
> range.  Measuring this in the presence of amps of RF would be a challenge
> (you're not going to do it with your current probe and oscilloscope for
> instance).  One approach might be to run the secondary current through an
> electrolytic cell and measure the amount of metal added or removed (like
> the old Edison Watthour meter).  You could get very long integration times
> this way so the change would be noticeable.  Measuring part per million
> values though (which is what you are doing) is never easy.
> 
>> 
>> 
>> What happens if you put a DC supply - several kV, in
>> series with the base, to provide a genuine DC component to the
>> topload charge, in the way that Robert describes - does that do
>> anything to enhance the performance?
> 
> This is an intriguing idea.  Especially if you were to make the voltage a
> significant fraction of the topload voltage during breakout, so that you
> would effectively be favoring one polarity of leader.  I'll bet you would
> notice a change in the nature of the streamers and sparks depending on the
> polarity, since there is a well documented difference for corona discharge.
> 
> You'd want a good RF bypass cap across the power supply, or the series
> impedance of the power supply would dominate. Most HV supplies use some
> form of multiplier/filter arrangement, not known for great RF performance.
> An RF choke would also be useful...
> 
> Hmmmm... one of those HV brick supplies that put out several mA at 10-20 kV
> from a copier..
> 
> You'd want a small TC (low voltage) for this so you could really make a
> difference. A few kV out of 500 kV on a big coil might not make a
> difference.  10-20 kV out of 75-100 kV though...
> 
> 
>> 
>> So many TC frontiers...so much real work to do.
>> --
>> Paul Nicholson
>> --
> 
> 
>