High Voltage but Low Current fuses...

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>

Hi All,

My differential probes and cap life test seem to require fuses with the 
following characteristics:

1.  ~30000 V withstand and break.

2.  About 250mA of fuse current, but NOT at all critical.  The current is 
either 100 mA (normal) or 500 amps (Yipps!!  turn it 
off!!)  ;-))  Basically a far "much less than 1 amp" but very high voltage 
fuse...

3.  A few amps of break current.  If say a pulse cap were to discharge 
though it, the current might be very high briefly, but it would quickly 
drain off.  Hi instantaneous currents are ok, but the sustained current the 
fuse would need to stop are low like a few amps (MOT).

MOVs can take a hit, but then the current needs to "stop" before they burn 
up...

4.  Cheap ;-))  Maybe something a person could just make themselves or find 
at some easy to by from source (web sales and "individual" purchasers ok).

I was thinking of winding a long thin wire on a "star" form in a long 
spiral to provide many break points and a long arc path would work.  I hear 
that putting it in baking soda or sand helps...  I see people drawing those 
big six inch arcs of a MOT which is "bad" for a fuse that has to stop such 
arcs...  A fuse on the MOT would stop that 20 amp draw on the primary...

Any ideas are welcome.  Both of my little projects seem to need darn good 
high voltage fuses...  The fuses themselves might become the third project 
;-))

Cheers,

	Terry