Re: Marx generator (fwd)

["High Voltage list" <hvlist@xxxxxxxxxx>]

Original poster: <sroys@xxxxxxxxxxxxxxxxx>



---------- Forwarded message ----------
Date: Tue, 22 Nov 2005 10:33:54 +0100
From: Herwig Roscher <herwig.roscher@xxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: Marx generator (fwd)



Malcolm Watts wrote to the High Voltage list:

> In theory, mine should have been 250 - 300kV when 
> erected. I got about  7" sparks.
 
Hi Malcolm,

This is 0.023" / kV. As my system produces 0.027" / kV, I'm in the 
ball park  :-)

> Gap settings are rather critical.
For a loading voltage of 20 kV, I set all spark gaps to 0.28". This 
is enough not to cause any premature ignition. The spark gaps consist 
of brass balls of 0.04" diameter. IMO any larger distance would 
increase the losses unnecessarily - correct?

> Ideally the it should erect from bottom to top. I didn't bother with
> triggered gaps. 
Using a trigger should ensure, that the erection will start from the 
bottom. The optic impression(sic!) is that the erection runs upward 
correctly.

In order to test, if  corona is a problem when the bank is erected, I 
soldered a 2" piece of thin wire to the HV - output and bent it 
perpendicular to the main discharge path. To my surprise there was no 
reduction in the discharge length. Therefor I assume that "HV-corona" 
is not a problem.

Any comments are very welcome.









> Hi Herwig,
> 
> On 21 Nov 2005, at 11:55, High Voltage list wrote:
> 
> > Original poster: <sroys@xxxxxxxxxxxxxxxxx>
> > 
> > 
> > 
> > ---------- Forwarded message ----------
> > Date: Fri, 18 Nov 2005 13:11:52 +0100
> > From: Herwig Roscher <herwig.roscher@xxxxxx>
> > To: hvlist@xxxxxxxxxx
> > Subject: Marx generator
> > 
> > 
> > List,
> > 
> > I have just finished building my first Marx generator and I am about
> > tuning it.
> > 
> > Capacitors			3.33 nF
> > Resistors			2 MOhm
> > Stages 			25
> > Loading voltage	20 kV
> > Spark gaps		0.28"
> > Erected C			133 pF
> > Bang voltage		500 kV
> > Bang size			16 Joule
> > Discharge length	13.4"
> > 
> > However I would like to ask the more experienced builders for some
> > help:
> > 
> > Q1:
> > The distance, a voltage of 1 kV can jump, usually is said to be 
> > 0.013". For Marx generators I found values of about 0.04" as well.
> > 
> > Other Marx builders claim:
> > 
> > 0.052"		Rapp
> > 0.045"		Steve Ward
> > 0.052"		Kronjaeger
> > 0.050"		Mike Gilchrist
> > 
> > My system jumps only 0.027"/kV. Why? Is this a question of the form of
> > the electrodes?
> 
> I built two some time ago. The caps were about 7nF each, dry-fired 
> rolled poly. I was using chokes instead of resistors for charging. 
> Total energy was about 14J.
>  
> > Q2:
> > Other Marx builders get:
> > 
> > 1.75"/Joule		Rapp
> > 1.92"/Joule		Steve Ward
> > 1.83"/Joule		Mike Gilchrist
> > 
> > I only get 0.9"/Joule. Again: Why?
> > 
> > Q3:
> > During and after completion of the bank loading there is no sizzling
> > noise. Therefor I assume, that there is little or no corona at 20 kV.
> > Is it possible, that at ignition of the bank there is too much corona
> > at 500 kV?
> > 
> > What are the secrets of Marx tuning? Any help would be appreciated
> > very much.
> 
> Malcolm
> 
> 
> 
> 
> 
> -- 
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Bye		Herwig

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Greed is the root of all evil !
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