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Re: [Amps] HV Fuses

To: Jim Thomson <Jim.thom@telus.net>, "amps@contesting.com" <amps@contesting.com>
Subject: Re: [Amps] HV Fuses
From: "Fuqua, Bill L" <wlfuqu00@uky.edu>
Date: Wed, 17 Feb 2010 06:17:47 -0500
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Shorting the B+ to ground is exactly what a crowbar protector does!!!!!
You discharge the supply allowing something else like a fuse that may explode 
if need be 
to protect the tube.


Bill
________________________________________
From: amps-bounces@contesting.com [amps-bounces@contesting.com] On Behalf Of 
Jim Thomson [Jim.thom@telus.net]
Sent: Wednesday, February 17, 2010 4:46 AM
To: amps@contesting.com
Subject: [Amps] HV Fuses

Date: Wed, 17 Feb 2010 01:49:25 -0500
From: "Fuqua, Bill L" <wlfuqu00@uky.edu>
Subject: Re: [Amps] HV Fuses

   I have thought a #30 wire or somewhat smaller wire was stretched inside a 
grounded piece of copper
pipe  such that there would be no discharge when HV was applied would be a 
great fuse. This is because if
an arc in the tube  would vaporize the wire and producing a plasma that would 
short the B+ to
ground via the surrounding copper tube or pipe.  Also, it would be easy to 
replace.

73
Bill wa4lav

## This exactly what u don't want to do.  You would simply coat the insides of 
the copper tube with vapour
deposit.  You would also grnd out the B+.   We  want the HV fuse to INTERUPT 
the  current... not
sustain it till something else blows up.

##  Home made   HV fuses, as larry suggest.. will work fb.  I simply put one 
fine strand  between  2 x standoffs,
and when machine screws are tight... the fuse wire will  be TAUT.   OK, now you 
wrap the exposed fuse wire
, loosely with 88 tape, and heat shrink tubing is even better.   Fuse blows.... 
no mess, it's that simple.

### BTW.... SSON  has  loads of  surplus  BUSS  HVU-3   HV fuses... $3-5  
each.. depending on qty.
I bought a case load of em.. since they were the exact size I wanted.   Each 
fuse is still in it's individual
box, sealed.   5 kv /  50 ohm glitch R  =  100 A  of fault current.   100A  
will  blow that  3 A sand fuse
HVU-3.... very quickly... < 2 msecs.

##  SSON  also has a lot of other  HV  fuses available.. which  might fit a 
specific application.

later.... Jim   VE7RF


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