Re: Streamer Voltage

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

Original poster: "Paul Marshall by way of Terry Fritz <teslalist-at-qwest-dot-net>" <klugmann-at-hotmail-dot-com>

Several years ago myself and a friend Bill Pollack used a Frequency 
generator and an Ocilliscope to determine some of the charateristics of my 
4" coil. The frequency was 285 kHz the way I remember it. We established a 
22.5 to 1 ratio between the primary and secondary by ringing the primary 
with the signal generator and measuring the secondary output to ground. 
This would mean that my coil was outputing 450 kV. I gererally ran my coil 
at 6 - 8 kW and got 60" streamers.



Paul S. Marshall





>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Re: Streamer Voltage
>Date: Wed, 07 May 2003 12:42:34 -0600
>
>Original poster: "Jim Lux by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
><jimlux-at-earthlink-dot-net>
>
>At 07:44 AM 5/7/2003 -0600, you wrote:
>>Original poster: "Harold Weiss by way of Terry Fritz 
>><teslalist-at-qwest-dot-net>" <hweiss-at-new.rr-dot-com>
>
>Distance is only proportional to voltage for uniform fields.  The more 
>non-uniform the field, the more it deviates from some nice cm/kV metric.
>Once you get into non-uniform fields and spark discharge... loosely, 
>anything where the radius of curvature is much less than 1 cm per 30 kV, 
>things like stored energy and the RF properties of the source start to 
>play a big effect.  The pulsed/RF nature of tesla coils is also significant.
>
>
>For a DC source (i.e. something like a Van deGraaff generator), the 
>voltage will stabilize at roughly that where the surface field is 31 
>kV/cm... A 6" sphere (15 cm diameter) has a radius of 7.5 cm, so when the 
>voltage  gets to around 230 kV, the corona losses will start to radically 
>increase as the air breaks down at the surface.
>
>
>The voltage drop along a streamer is a different matter, and depends very 
>much on the current flowing in the streamer.  A typical lightning stroke 
>at 10 kA has a voltage drop of about 1000 V/meter.  To a first order, the 
>area of the spark channel and hence the resistance, is proportional to current.
>
>
>
>>Hi All,
>>
>>This has been bugging me for a while. Is the streamer voltage measured by 
>>the combination of topload geometry plus streamer length, or just by 
>>streamer length?  With my 4" coils, the 6" sphere had a breakdown voltage 
>>of 571KV by Sd=((MV/7.5)*2)*100.  Sd=sphere dia in cm.  MV= voltage in 
>>megavolts.  It's 18" streamer would come to 502.92KV at 1.1KV/mm.  If the 
>>two add together it would make the total voltage 1MV+.  If it were just 
>>streamer length the 502KV would not even produce corona on the 
>>sphere.  Or could it be that, the voltage peaks enough to produce corona, 
>>and then drops, as the streamer is formed.
>>
>>David E Weiss
>