[Amps] HV Fuses

Roger sub1 at rogerhalstead.com
Wed Feb 17 04:30:14 PST 2010

Angel Vilaseca wrote:
> Just another idea...
> In the old car ignitions there was a capacitor in parallel between the 
> points. This was made to avoid an arc between the points when the point 
> were switching off 12 Volts into the coil primary.
If you are talking about the cap in the distributor, this cap stored 
energy and then released it when the points opened. That provided the 
pulse to the primary of the ignition coil. Without that cap the spark 
provided was pretty anemic.


Roger (K8RI)
> What we are trying to avoid in an HV fuse is also an arc when the 
> circuit breaks (wnen the fuse melts).
> So how about using an HV capacitor in parallel with the fuse? would that 
> keep an arc from appearing?
> Anyone tried this?
> Angel Vilaseca HB9SLV
> K1SG at aol.com a écrit :
>> 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 at AOL.com
>> 508-435-9133
>> FN42fe  
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