Re: Variac blowing fuses (another newbie questin)

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Steve Ward <steve.ward@xxxxxxxxx>

> - Original fuse was 20A - don't know whether it was fast or slow
> blow.  Replacement fuse was 15A SLOW BLOW.  When it blew, the solder
> breached the fuse's glass cylinder.

Interesting.  Most of the time, whe fuses fail from say 150% overload
they dont vaporize like that, usually only fault conditions cause
that.

>
> - The fuse blows after I've dialed the variac up to full power from
> zero. It didn't blow immediately - rather, the coil ran for maybe
> 10-20 seconds.  I believe the variac was up to full power.  Both
> times, the fuse blew during strong continuous arc to grounded
> target.  Hasn't happened when streamers were not striking
> anything.  I always power up starting the variac at zero.

Ah hah, perhaps these arcs to your grounded target are producing
transients, perhaps sufficient enough to cause an intermittent arc
between mains HOT and ground.  Ive seen this happen with my DRSSTCs!
The result is a very bright explosion across my terminal strip and a
nice "pop", didnt trip breakers (the arc extinguished quickly) but
would surely blow a fuse.

Im not certain, but it sounds like you have something out of the
ordinary happening here, and you maybe arent exceeding the fuse rating
under normal cases.

Steve Ward