Re: Marx generator (fwd)

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

Original poster: <sroys@xxxxxxxxxxxxxxxxx>



---------- Forwarded message ----------
Date: Mon, 21 Nov 2005 22:49:52 +0000
From: Mike Harrison <mike@xxxxxxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: Marx generator (fwd)

On Mon, 21 Nov 2005 14:26:13 -0700 (MST), you wrote:

>Original poster: <sroys@xxxxxxxxxxxxxxxxx>
>
>
>
>---------- Forwarded message ----------
>Date: Tue, 22 Nov 2005 09:07:51 +1300
>From: Malcolm Watts <m.j.watts@xxxxxxxxxxxx>
>To: High Voltage list <hvlist@xxxxxxxxxx>
>Subject: Re: Marx generator (fwd)
>
>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. In theory, mine should have been 250 - 300kV when 
>erected. The uncertainty is in the gap firing voltage/s. I got about 
>7" sparks. 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.
>
>Gap settings are rather critical. Ideally the it should erect from 
>bottom to top. I didn't bother with triggered gaps.
 
A triggered gap of some sort makes the gap settings WAY less critical, as they only need to not fire
at Vin, and fire at 2*Vin so there os plenty of latitude