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Variac blowing fuses (another newbie questin)
Original poster: otmaskin5@xxxxxxx
Thx for all the responses. Several of you asked for more info in
order to diagnose. Here's the info.
- The variac is supplying power to the NST only
- 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.
- 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.
- The variac provides 0-130 volts out. Current rating is 20 amp.
- Fuse appears to be located in the input circuit of the variac (not
totally sure as I wasn't able to get the cover off far enough to
thoroughly examine the wiring).
- I don't know whether the NST is a high power factor type or a
normal. I'll check with the
mfg to see if I can find out. In the mean time, it's a Franceformer,
15000 volt, 60 ma, 890 VA, model # 15060.
- My tesla coil has a static spark gap. 9 gaps made of 3/4" copper
pipe 0.03" for each gap. So far, its wired to use only 4 gaps (0.12"
total) and small fan for quenching.
- The value of my tank capacitor is 0.03 uF +10%, 35KV. I'ts the
Maxwell cap you see on eBay quite often.
- The variac works (as indicated by the voltmeter) without blowing
fuses @ no load. Also, I run my small coil (9/30 NST powered) using
the variac haven't blown fuses.
Hope this helps in figuring it out. Thanks.