[Amps] HV Fuses

[Fuqua, Bill L]

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

Date: Wed, 17 Feb 2010 01:49:25 -0500
From: "Fuqua, Bill L" <wlfuqu00 at 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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