Re: [Tesla-2] High Power Factor Neon Transformers

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

Original poster: "Jim Mora by way of Terry Fritz <twftesla-at-qwest-dot-net>" <jmora-at-jetlink-dot-net>

Thanks Bert,

You shed much light on  PFC, though I am still concerned about the output "P"
due to power correction and the somewhat PFC loss effect of the .0212 uf MMC
tank. I must be missing something here.

The tank caps are tuned to resonate with the xformer effectively that approach
nearly eliminating the shunts? Yes?

Without getting too deep into this, will the recommended tank capacity still
allow for maximum power transfer (1800 Va), or did I buy a second boat anchor
to lug outside? I guess I'm lost in the -J plane, but I believe in the
conservation of energy theory ;-).

Know that I am running a dedicated circuit from my over designed main. And
since I live in California, we live with candle power most of the time:-) I can
afford to draw excess power now and then.

The bottom line here is: given there is loss across the dual PFC's, will my
effective power to the coil be halved and will the tank resonate at optimum? Be
patient with me, I started with vacuum tubes and my razor is becoming dull :-)

Jim

Bert Hickman wrote:

> Hi Jim,
>
> In order to limit short circuit current, all neon sign transformers (NST's)
> use internal magnetic shunts (small core laminations) to shunt some of the
> magnetic flux, reducing the degree of electromagnetic coupling between the
> primary and secondary windings. These shunts have the effect of adding
> significant "leakage inductance". This means that the primary winding of an
> uncorrected NST will appear to be very inductive - and the incoming current
> and voltage will be significantly out of phase with one another.
>
> "Power Factor Corrected" or "High Power Factor" NST's use an additional
> internal winding and HV AC
> capacitor to help compensate for much of the inductive effect, bringing the
> primary current and voltage more closely into phase with one another,
> thereby reducing the peak current demand of the transformer. A corrected
> NST will typically consume half the input current of an uncorrected one
> (i.e. half the volt-amperes) while delivering the same output power (in
> watts). This can be seen in Transco's Tube Footage Chart - an uncorrected
> 15kV/60mA transformer will pull 900 volt-amperes (VA) on the primary side,
> while a High Power Factor NST will only draw 464 VA. Although a 15 kV 60 MA
> transformer will deliver 15 kV at 0 mA or 60 mA at 0 volts.. the current
> limiting function prevents it from delivering 15 kV AND 60 mA at the same
> time. That's why you'll never actually get 900 VA out of a 15/60 - only
> about half that, irrespective of whether you use PFC or not.
> See Transco's chart at:
>    http://www.transco-neon-dot-com/tfoot.htm
> BTW, some fairly good explanations about NST and Ignition transformer
> design and behavior can be found on France's web site at:
> http://www.franceformer-dot-com/faqsearch.asp
>
> Many coilers add external power factor correction capacitors across the
> primaries of non-corrected NST's to achieve a similar reduction in incoming
> current. However, when you add your MMC tank cap to the secondary side, you
> also get a degree of power factor correction, since the capacitive load on
> the secondary side also tends to partially cancel the NST's leakage
> inductance. This reduces the magnitude of PFC capacitance that would
> otherwise be necessary on the primary side of the NST. Most coilers find
> that they really need only about half of the PFC capacitance that would be
> necessary if the NST were driving a non-reactive load (i.e., a luminous gas
> tube). Since the NST designers assume the NST would always see a gas tube
> load, a PFC-corrected transformers will tend to "overcorrect" in Tesla Coil
> use. While this will likely not cause any significant problems during coil
> operation, I'd recommend buying NON power factor-corrected NST's, since
> they're cheaper. You can always add external PFC capacitance until you get
> the desired degree of correction. Note that it's not essential that you use
> PFC, and doing so will not improve your coil's performance. But, it may
> allow you to lower your coil's current demand so that you avoid popping
> breakers or fuses.
>
> Good luck on your first light!
>
> -- Bert --
> --
> Bert Hickman
> Stoneridge Engineering
> Email:    bert.hickman-at-aquila-dot-net
> Web Site: http://www.teslamania-dot-com
>
> Jim Mora wrote:
> >
> > Hello All,
> >
> > I have two paralleled Transco "high power factor" 15/60 transformers.
> > The threads on this issue verses a "normal" power factor one seem vague
> > at best to me. Is "high power factor" power phase correction or some
> > change in shunting differing by manufacturer?
> >
> > I do know that the corrected V/I phase drops the mains draw by a factor
> > almost 50%; but, I checked the Transco site and found that even though
> > they are delivering (2x) 60/15 -at- .06 amps, the output "capacity" drops
> > from 1800 to 927 VA.Hmm.
> >
> > If this is a result of the current / voltage phasing, what would likely
> > be the effect of my Panasonic .0212 mmc cap bank to this adjusted VA
> > rating and the charge/discharge and cap values be? (I also have a .01
> > geek group bank at hand).
> >
> > France Xformer's site has lots more information on the input side but
> > none on the output effects. Can someone shed some light (or bolts:) on
> > this issue. I am nearing first light and will want to try to exchange
> > $380 worth of the Transco's before I fire the coil.
> >
> > Thanks,
> > Jim Mora, Fillmore School District, AE
> >
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