Re: [Amps] HV fuse

[Bill Fuqua <wlfuqu00@uky.edu>]

I have thought about fabricating a device to protect tubes. Eimac claims 
that if your crow bar circuit will protect a piece of  #30  copper wire 
under short conditions it will protect the tube.
   What if you stretched a piece of #30 bare wire thru the center of a 
piece of well grounded copper tubing. If your tube should flash over the 
#30 or maybe #32 wire would vaporize and the vapor would immediately 
conduct the current to the surrounding tubing rather than to the tube. or 
put your sacrificial current limiting resistor in the center of the tube so 
it would not only limit the peak current but also produce a plasma 
conduction path to ground.
73
Bill wa4lav


At 04:08 AM 7/13/2004 -0700, R.Measures wrote:
> ?  The trouble with high voltage fuses is that the metal vapor   arc which 
> forms as the fusing wire melts has only c. 30v drop.  However, a low-ESR 
> 3000v filter C can still do plenty of damage at 2970v, so a foolproof 
> means of limiting I-peak is needed.  In other words, the device that the 
> HV fuse is supposed to be protecting from a current spike is not protected 
> for a finite period of time, and damage may result.
> -  A better solution is to limit I-peak with a suitable HV glitch R and 
> use circuit breakers, or 250v fuses, in the primaries of the PS transformers.
> cheerz, Lane
>
> On Jul 12, 2004, at 5:11 PM, Lane Zeitler wrote:
>
> > Gents,
> > Anyone remember what wire size to use for a HV fuse??? Looking for 
> > something that will pop at around 2 amps.
> >
> > Lane
> > Ku7i
> >
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> Richard L. Measures, AG6K, 805.386.3734.  www.somis.org
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