Re: Cap Selection

Hi Kevin,

> I was considering getting 2 .05uf 25kv caps. that way I could use them in
> series or parrallel to get different values in the future. I would like to explore
> the balanced primary design, too. In addition I have several xray xfmrs 100&120kv-at-200ma.
> Maybe I could put the caps in series to form a .025uf 50kv for use with
> these.  (only powering 1/2 leg of xfmr pri for 50kv out) With those 2 caps I could
> hit a few stones with a couple birds. What do you guys think?

It would be a very high voltage on the primary indeed.  The cost of the 2 caps would be
enourmous indeed though.  If your willing to spend the bucks, I will wait for your results.
I gues my thinking is if you want to get to longer spark lengths, why not go to larger
primaries and smaller capacitors.  You could save yourself a wad of cash, and increase your
coupling capabilities at the same time.

> Question: Will that be enough, or should I opt for more?

In a classic Tesla coil design, you can certainly suck up the power.  A 100 amp service would
handle almost anything the average person can build.  You should be able to acheive 20'-25'
arcs with that much power, with an efficient coil design.  However, if you are after longer
sparks, especially over 15', perhaps Tesla magnifiers should be considered.  In general, You
can get sparks as long as a classic coil with 1/4 the power input.  That is why Tesla himself
abondoned the classic coil design for the three coil magnifier set-up.  It is much more
efficient.  But, if you can have a 200 Amp service installed for no more (or little more) money,
I would do it.  I adds to the value of the structure.

> The hookup is free and it will only cost me a minimum $10/month service fee
> (plus electric used).I just have to provide a meter housing and conduit to the
> roof.

My advice here is bury the line.  If you ever want to run your coil outside, you don't want
an overhead line interfering with where you can place your coil.  I learned this the hard
way. :-(

> My next step (I am in the process of)is finding a pole or pt xfmr. If I get a deal
> or get one free will be the determining factor as to what power level I get.
> Question: Am I right in thinking that I can not plan on a big one and throttling back on
> it, because you must have a certain amount of power running through it for it to work at
> all? Is there a certain percentage range of power that a particular xfmr can be used for?

No, a PT or Pole transformer is a "black box".  Power in = Power out.  I'm sure you will
run a couple of KVA anyway, so these transformers are the right choice.  The pole type is the
best choice because it can take the most abuse.  You can also run them over their rating
intermittently without damage.

Scott Myers