Re: unknown prob

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

Original poster: "Gregory Hunter by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ghunter31014-at-yahoo-dot-com>


> Hi All,
>  
> I was experimenting earlier on today with a new MMC
> that I am building, on
> connecting the new MMC I blew the transformer
> :-(((((((.....
>  
>  
> The MMC was not wired to the Tesla coil at all, I
> removed the Filter circuits
> from the HV side of the transformer... and wired it
> as follows
>  
> HV SIDE
>  
> NST transformer
>  
> 1) HT1 on transformer to MMC
> 2) MMC to spark gap
> 3) Spark gap to HT2 on transformer.
>  
> any ideas
>  
> Duncan
> 
I think you have just demonstrated 50Hz mains
resonance. I think the high voltage buildup ruined
your NST. I had a similar experience while attempting
to "test" a 6.6nF wine bottle cap using only a
15kv/30ma NST and no other load on a 50Hz mains
circuit. I kept puncturing bottles, which really
puzzled me. I eventually got four high-strength
bottles together that resisted HV puncture. Instead, a
spark from one NST terminal jumped AROUND the ceramic
insulator--a length of some 3 inches--to the case of
the NST! I could not have been more amazed if the
thing had reached out and slapped me ( I believe
"gobsmacked" is the correct British-ism). I quickly
killed the power. Somehow, my brand new Transco epoxy
potted NST was spared. So what caused this bizarre
event? Easy. The NST secondary and the bottle cap
formed a low loss 50Hz resonant circuit. The
oscillating current built up amplitude, like a
flywheel gone mad, until the voltage buildup
overwhelmed the insulator. If you ever try this again,
I suggest placing a safety gap in parallel with the
MMC--although this sort of low inductance discharge is
incredibly hard on the MMC and may exceed it's dv/dt
rating. Probably the best place to test an NST and an
MMC is in a working Tesla coil.

Regards,


=====
Gregory R. Hunter

http://hot-streamer-dot-com/greg

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