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Re: Odd Variac Control And Transformer Really Buzzing ??

Hi Bill,

At 06:05 AM 03/07/2000 -0500, you wrote:
>
>Greetings,
>
>I got my first MMC built. :-)  Thanks Again Terry.
>I am now able to power the coil with AC rather than
>DC.  By the way performance does seem to be up.

Great!!

>
>Transformer is 9kv-at-30ma NST.
>If my spark gap does not fire right away when I hit
>the power to the Variac then the NST starts groaning
>really loud.  Turning up the Variac does not get the
>gap firing it just makes the NST groan more.  

I have done this too.  With large caps hooked to NSTs, The voltage and
current can rise to very high levels if the gap does not fire.  I think
this causes saturation of the shunts and cores of the transformer so it
draws far more current than expected.  It is on my list to look into this
more but perhaps this effect can be used to get still more power out of an
NST.  In the mean time, put the main gap closer so it fires before this
groaning state is reached or use a little less capacitance.  This high
current is probably not good for the NST windings as they may overheat very
quickly.  I have started using fuses on NST inputs to insure that high
input currents will not be sustained under this condition.

>
>If I turn the variac off and wait a couple of seconds
>and pop the power to it.  The gap starts firing and
>streamers a flowing.  

I wonder if the saturation causes the output voltage to fall off.  Thus,
the NST could be thrown into sort of a "melt down" state?? - Interesting.

Cheers,

	Terry

snip...
>
>Thanks In Advance,
>Bill Parn
>