Re: REVISED Need NST

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Terry,
          Although I plead guilty to having used NSTs on occasions, I 
also wind transformers for TC use. There is a simple technique you 
can use to avoid having to (a) use an external ballast, and (b) avoid 
the use of shunts. Simply put one winding on one leg of a C-C core 
and the other on the opposite leg. Physical separation of the 
windings ensures there is plenty of leakage inductance built in and 
as a bonus, electrical isolation between windings is improved, 
especially if the core is grounded *to the mains ground*.

Regards,
malcolm



On 26 Sep 2001, at 19:14, Tesla list wrote:

> Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
> 
> Hi Jim,
> 
> Some of the "pro" coilers do have custom transformers made and the prices
> are not bad at all ~$1000 for that perfect high-pot guaranteed, well over
> designed, just the right size..., HV transformer.  Of course, the average
> fella buying in quantities of "one" and not knowing the fancy technical
> details they ask, does not have a chance...  Far easier and cheaper just to
> adapt one's coil plans to common transformers.  As you say, potential
> transformers are very attractive.  Finn is on of the gifted few who
> actually has made his beautiful transformer from scratch.  But most of us
> are not that good ;-))
> 
> The custom made trannies typically use external inductive reactors for
> current limiting since that is much easier and cheaper than making a true
> shunted core transformer in small numbers.  The details are easy for a
> transformer house and your price tends to depend only on quantities and
> weight since the house engineer can probably "design" it in minutes...
> 
> If one already has a big core, then rewinding it is not a great technical
> challenge but the problems is just in getting and winding all that wire and
> perhaps making an oil bath enclosure.  With nice rebuilt pigs running
> around $300 bucks, such effort are usually not worth it.
> 
> Cheers,
> 
> 	Terry
> 
> 
> At 05:53 PM 9/26/2001 -0700, you wrote:
> >Actually, much as for capacitors, nobody is interested in selling to the 
> >Tesla Coiler market, per se.  We tend to be pretty hard on the equipment, 
> >with overvoltages, transients, etc., not to mention that your basic TC 
> >design isn't what you would call well controlled and well defined in terms 
> >of requirements.
> >
> >Interestingly, when I was buying some big HV transformers from Peter
Dahl (a 
> >small/medium builder of custom HV transformers, mostly for the radio 
> >transmitter market in the 2-10 kVA range), they mentioned that they hated 
> >dealing with Tesla Coilers... They wanted cheap transformers, had no
idea of 
> >the real requirements, and tended to send back the transformer for warranty 
> >after having destroyed it either by overloading or overvoltage. 
> >
> >
> >There ARE multi-million dollar companies making transformers for the TC 
> >market: Actown, France, Allanson, etc. for high leakage inductance current 
> >limited units; and GE, Magnetek, ABB, Siemens, etc., for the higher power, 
> >non current limited unit.
> >
> >And, their products are quite reasonably priced for NEW units built to some 
> >consistent catalog specifications (which may or may not align with what
a TC 
> >builder might want).
> >
> >A few years back, I actually put some thought into what the "ideal" 
> >transformer specs for a TC might be.  Say, 110V in, 10-15 kV out, around
1-2 
> >kVA. As it happens, standard commercial potential transformers happen to
fit 
> >the bill quite well, and are reasonably priced on both the new and used
> market.
> >
> >Granted "reasonable" from a manufacturing cost and retail markup standpoint 
> >(i.e. several hundred dollars) might not be "reasonable" for a hobby 
> >scrounger, but, just the cost of the iron and copper in a decent
transformer 
> >is a pretty sizable chunk of cash, and adding the R&D cost, assembly, 
> >testing, quality control, shipping, etc. and it adds up.  For these
sorts of 
> >things, if you figure that the raw parts cost is roughly 1/10th of the 
> >retail price, you won't be far off.  If you've bought enameled copper wire 
> >new, you realize that $30 for the parts cost on a 5 kVA pole pig probably 
> >isn't unrealistic
> >
> >Tesla list wrote:
> >> 
> >> Original poster: "mbarbani by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
> ><mbarbani-at-yahoo-dot-com>
> >> 
> >> Welcome to the world of Tesla coil building..where very little is
cheap or 
> >easy
> >> to come by! The Neon Sign Transformer--manufactured exclusively for, you
> >> guessed it, neon signs..not Tesla coils! That's the pickle we're all in, 
> >and if
> >> some company were to make transformers especially for our coils it
would no
> >> doubt be a multi-million dollar outfit by now. I got my NST from a
sign shop
> >> for $25..not free like some say. Only thing I can say is don't give up! 
> >You are
> >> destined to find one. Good luck and Godspeed in your quest! Marc B.
> >> 
> >> Do You Yahoo!?
> >> Get email alerts & NEW webcam video instant messaging with
> >> <http://rd.yahoo-dot-com/mail_us/tag/?http://im.yahoo-dot-com/>Yahoo! Messenger.
> >
> 
> 
>