[Amps] HV fuse

[R.Measures]

On Jul 23, 2004, at 1:19 AM, peter.chadwick at Zarlink.Com wrote:

>
>
>
>
> Rich said:
>
>> HV fuses normally contain silica sand to quench the metal vapor arc.
>
> Asbestos powder has also been used in the past, but not these days. The
> filling is called 'anti rupture powder': the idea is to keep the fuse 
> wire
> intact although molten until it reaches a sufficiently high 
> temperature to
> explode apart. It's not just used in high voltage fuses, either, but 
> where
> you need a high fault current interruption capability. Interesting 
> subject,
> fuses.
>
> Personally, I've found that suitable thin wire between two ceramic
> insulators is quite adequate: insulator about 4 inches apart and the 
> wire
> not too tight between them, and about 42awg. In the event of an arc 
> (and I
> also use a 50 ohm, 100 watt, 12 inch long wirewound glitch resistor) 
> the
> wire just disappears. Of course, you need to allow plenty of clearance
> around the insulators:  I have 4 inch high insulators mounted 
> horizontally
> so the wire falls away from them, although teh few occasions it has 
> failed,
> I've never found enough signs of any wire to judge where it did go.

Hello, Peter --
   Have you ever performed the big screwdriver short to chassis fault 
test to see how well the 4-inch fuse wire limits the peak current 
produced by the filter-C?  What purpose does the in-air fuse wire 
serve?
>
> 73
>
> Peter G3RZP
>
>
>
Richard L. Measures, AG6K, 805.386.3734.  www.somis.org