Why not fuse the negative lead instead, which is at potential close to
ground? If you do this, you need to be sure the HV ammeter shunt is on
the power supply side of the fuse and not the "load" side, so that point
remains close to ground even when the fuse blows....
Or use primary fuses or circuit breakers to protect against major
faults, and a B+ glitch resistor to protect against momentary tube
arcs...?
-----Original Message-----
From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]
On Behalf Of K1SG@aol.com
Sent: Tuesday, February 16, 2010 3:59 PM
To: amps@contesting.com
Subject: [Amps] HV Fuses
In recent threads, there have been a number of comments about high
voltage
fuses.
Carl mentioned sand-filled fuses, something I hadn't heard of.
I checked the Mouser catalog for HV fuses, and was stricken with
sticker-shock...$38 for a fuse?
OK, we re-think this one...
I know that an old but workable approach is to use a thin piece of
wire
as a fuse...mount it between a couple of standoff insulators, and it
should
function fine, and if current is substantially too high, the fuse wire
blows. How do you figure the appropriate size wire to use? And then,
how do you
go about ordering 6" of #30 wire, or whatever it is? If you need more
current capacity, to use the above example, can I put two strands of
#30 wire
in parallel, and expect them to function as a reliable fuse? I'm
always
worried about kinking the wire, or if it's enameled, sanding off more
than
just the insulation.
The plan is to fuse the HV output of a 5KV 2A supply to a 3X3, which of
course will only be used at the legal limit or into a dummy load.
Steve Gilbert
K1SG
K1SG@AOL.com
508-435-9133
FN42fe
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