[Milsurplus] HV Fuses: You Were Right, I Was Wrong

[J. Forster]

The capacitor has to be able to absorb the L*I^2 energy of the circuit,
without charging up to a voltage big enough to sustain a metal plsma arc.
A 0.1 is nowhere near big enough, IMO.

The original designers were not dummies. They used long fuses because they
were needed.

-John

================





> And therein lies a partial answer.  Put a 1 or 2 KV 0.1 MF capacitor
> across the fuseholder to snub the reactive kick and it will likely not
> sustain any arc.
>
> HTH
> George
> W5VPQ
>
> ---------- Original Message ----------
> From: "J. Forster" <jfor at quikus.com>
> To: "David Stinson" <arc5 at ix.netcom.com>
> Cc: ARC-5 List <arc5 at mailman.qth.net>, milsurplus at mailman.qth.net
> Subject: Re: [Milsurplus] HV Fuses:  You Were Right, I Was Wrong
> Date: Fri, 15 Jun 2012 05:37:26 -0700 (PDT)
>
> Absolutely predictable. You could try several equal fuses in series. No
> guarantees though.
>
> HV DC really arcs, especially with any inductance in the circuit.
>
> -John
>
> =============
>
>
>
>
>> As you all probably remember, I did some testing using
>> Picofuses (tm)  to rebuild the BC-375 high-voltage
>> fuse links.   I "destruction tested" six or eight of them.
>> Each opened without problems.
>>
>> Wellll......
>>
>> One opened during my 211 tests due to a gassy tube.
>> No problem.
>> I replaced it with another rebuilt fuse.
>> Another gassy tube, but this time....
>> "ZZZZZZZZZZZZZZ!!..........." from inside the
>> dynamotor.  The Picofuse had opened, but fully carbonized
>> and was transformed into a nice spark gap.  I'm lucky
>> the inductive kick didn't take out any of the inductors.
>>
>> So.... You were Right.  I was Wrong.
>> Back to the drawing board.
>> Probably try 3AG pigtails mounted externally.
>>
>> 73 Dave AB5S
>>
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