Re: Lots of questions

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

Original poster: Bart Anderson <classi6-at-classictesla-dot-com> 

Hi Newell,

Glad to see you've joined up on TCML!

You'll notice experienced coilers are very "leery" of new coilers diving 
into pole pig transformers for a first coil because there are some "real 
dangers" involved. I've already mentioned this stuff off-line, so you know 
exactly where I stand on this issue.

I HIGHLY recommend an NST transformer first. Build the coil. Use the NST. 
Learn through doing. Then and only then go ahead and upgrade. If you get a 
pole pig first, "you will use it", and without some experience with TC 
operation (not only the transformers), you have much greater risk of life 
and limb. I don't know your experience with electrical or electronic 
components, assembly, and operations, but I would say the same thing to 
anyone asking these questions. Although 3 have died in some manner with 
Tesla Coils, no one I have heard of has died from advice off this List, at 
least, not yet. The one that does is likely to be one who takes risks or 
doesn't heed advice (may be one and the same). Consider this as coilers 
watching out for one another. I know this next bit may sound morbid, but I 
believe it's just a matter of time, and that scares me (and it could be any 
of us, not just new coilers). Let's face it, this is a "coil at your own 
risk" hobby.

More interspersed below:

Tesla list wrote:

>Original poster: "Newell Jensen" <pillar2012-at-hotmail-dot-com>
>Hello all,
>
>I am new to this process so I am trying to figure this all out, so please 
>bear with me if these questions seem off course.
>
>I have been contemplating in my head what I would need to do if I did 
>indeed in the future buy a pole pig.  One question is why don't people buy 
>pad transformers that have the same voltage ratings as a pole pig?

Coilers use all different types of transformers. Some of the more common 
types are NST's, MOTs, Potential, and Distribution. There are of course 
others which can be used. Typically, cost, availability, and practicality 
are key issues.

>Also I know that some pole pigs can be bought with taps and I am wondering 
>if this is going to be benefical in the end.  The one that I saw allowed 
>the pole pig to adjust to a level of + or - of 2% of it standard voltage.

Yes, most have taps to change the step-down voltage for line regulation (as 
is their intended use, up on a pole). We typically set the tap to it's 
highest output voltage.

>The pole pig that I am refering to by the way is a 10 KVA 14.4 KV single 
>phase pole mount transformer.

Yes, 5 kva and 10 kva are common  VA ratings for those that do have pole 
transformers and use them in this hobby.

>  Also when somebody finally gets one of these I have read that they are 
> going to have to ballast it with something like an arc welder to limit 
> the current.  If this is right, how does one go about doing that and what 
> are the specifics involved with the voltage and so forth? Also a variac 
> has been mentioned and how would this be included to the whole situation?

The ballast is typically "inductive" current limiting. Pole mount 
transformers are not internally current limited. In a short circuit 
condition, these transformers can draw many times their rated current. The 
percent impedance rating of the transformer is a rating of how beefy that 
current can be. For example, my transformer is rated at 1.9% impedance. 
1/1.9% = 52.6 x rated amps or 2,193 Amps! Thus, we limit the current.

Welders are common for this purpose, but you may want to check out the TCML 
archives for details at pupman-dot-com. Variacs are also common and is what I 
use. Between the voltage adjust variac and the transformer, I have 
connected in series a large variac which must have sufficient current 
capability for the current planning to be run. If the variac is large 
enough, it can be connected in series without modification to the variac. 
However, if the variac is border line, then a slot can be cut in the core 
material to prevent core saturation. If it's too small, it will fail, and 
probably fail shorted!

>Does all of this together equal the "power module" that has been mentioned 
>as well?

Terminology. From one view point, a power module can incorporate everything 
from the wall plug to the transformer. I like to separate these into 
"supply" and "control module". The control module would be comprised of the 
voltage adjust assy, current limit/adjust assy, any added resistive 
components (if used), possibly a second set of doublethrow breakers, power 
switch/lights, volt and amp meters, and any safety devices such as deadman 
switch/interlock, etc..

>   Also if in the future if I was to finally get one of these what size 
> should I make my coil, or would it matter since I have the control module 
> and can therefore adjust the power being supplied to the coil?

A large transformer can control a small or large coil. Here's a thought. 
Dr. R. is looking at having a professional transformer manufacturer build 
some robust NST type transformers for TC use. I believe this will be a big 
seller for a lot of coilers. I for one plan on at least 1 (maybe more).

>   I have been thinking of also of constructing a HV cap like the MMC that 
> I have seen on the web.  I have heard that they are the best.

Yes, they are ideal for TC use.

>I also hear people always addressing how much the diameter of there 
>secondary coil is and not the height of it.  Is there a certain height to 
>what the secondary should be and also what about the size of the primary?

Although you'll hear diameter mentioned, and even discussions on "ideal" 
secondary h/d ratios, the ratio which is between 4:1 and 5:1 is the most 
common. Other ratios will work, but there are many other aspects to 
consider, least of which are the sparks off the top. It's nice to keep them 
far as possible from the primary, without going overboard on length. Some 
have built tall coils and they worked fine. Others have had lousy 
performance. Low h/d ratios get to be impractical.

>   I know there are a lot of questions here and any help would be greatly 
> appreciated.  Thanks

Don't forget to hit the pupman archives.

Take care,
Bart


>Newell