Re: HV transformers and spark gaps

> I have access to an hv broadcast transmitter plate transformer, 
> transformers oou of microwave ovens, and possibly a pole pig or two. 
> would you recommend I use and why?

I should have such problems!  If you are just starting up with Tesla 
coils, you would probably be better off (and live longer) by building a 
couple of smaller coils using neon sign transformers before jumping 
into the real multi-kVA barn-burners.  WIth neons, everything is a lot 
simpler and you can "cut your teeth" on the problems you WILL 
encounter with a system that is not a certain fiery death if things get out 
of control and are not handled properly.  Realize that even a "small" 
coil running with neon sign transformers is capable of producing at 
least 2'-3' discharges and is probably generating peak instantaneous 
powers in the multi-hundred kVA or higher range, and as dpierson so 
graphically described it, you can think of every 745 VA as one large 
Clydesdale horse frolicking around in your lab.  Then stop and think 
about how large a herd you want to let loose in your garage (or 
basement, or where ever)!  Smaller coils will also get you familiar with 
the wiring, operation, tuning, tweaking, and all the other aspects of 
coiling that no amount of reading can prepare you for.

Given that disclaimer, if you're really set on producing white-hot, 
flaming 8' arcs the first time around, then the pole pigs would probably 
be your best bet.  They probably have a high enough voltage so you 
wouldn't have to wire them in series, and even if you do, you can run 
two in series and ground the center connection for a HV power supply 
that would run anything that you would probably ever make without 
your own substation.  Just remember that those transformers aren't 
current limited and will easily dim the neighborhood lights given half a 

Richard Hull of the Tesla Coil Builders of Richmond wrote an excellent  
two-part article in the TCBA newsletter a few years back on transformer 
selection, and I will post the vol/issue information when I get home and 
get a chance to look through my copies if no one beats me to the punch.

Steven Roys (sroys-at-radiology.ab.umd.edu)