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Considering Upgrading to Pole Transformer



Original poster: "Bill Vanyo by way of Terry Fritz <twftesla-at-qwest-dot-net>" <vanyo-at-echoes-dot-net>

Thinking about eventually getting a pig - probably a 5KVA, 120 to
14400.  Not soon, but I like to think and plan ahead, and of course, get
lots of advice first.  Main questions - suitable tank capacitor, type of
spark gap, and current limiting:

What are people using for caps with their pig systems?

Using the Geek group caps (Cornell-Dubiler 942C20P15K, 0.15uF, 2000VDC),
what would be the dimensions (number of strings and string length) for a
suitable MMC?

I'm currently building 8 strings of 11 (with a 9th spare string) for a
very LTR cap for use with four 15/60 NST's and a sync triggered gap. 
Would this suffice?  I know LTR is easier on the NST's --- is  there any
need to use an LTR cap with a pole transformer?  And I geuss the answer
to that might depend on what type of spark gap I use (synchronous, async
rotary, or static).

So, which type of spark gap is easiest on the tank cap? (and I assume I
don't have to ask about what's easy on the transformer, correct?)

Last, current limiting.  I have a variac rated 240 volts, 50 amps, but
don't want to modify it in any way - just want it for input voltage
control.  I've heard of people using arc welders for inductive ballast -
I don't have one.  Can NST's be used?  Could one use one or more
depotted 15/60 NST's, (perhaps with secondaries removed?), and add or
remove the NST's current limiting shunts to adjust current?  I think I
also read that inductive ballast alone doesn't work too well, that there
should be a resistive element also.  Any pointers on how this is done,
or how necessary it is?

Are people using PFC caps with pole transformers?

For my NST setup, I've been using a 240 volt 30 amp house line (electric
clothes dryer), stepped down to 120 volt with the variac, to power the
NST bank.  Would this be adequate for powering a pig?

	Thanks,
	Bill Vanyo