[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [TCML] Toroid question
140 volts into a 120 volt transformer is not a 25% overvolting. 140/120 = 1.167 or 16.7%. Most of us have variacs that do this, so we do.
Adam
--- On Thu, 6/4/09, Dex Dexter <dexterlabs@xxxxxxxxxxx> wrote:
> From: Dex Dexter <dexterlabs@xxxxxxxxxxx>
> Subject: Re: [TCML] Toroid question
> To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
> Date: Thursday, June 4, 2009, 2:57 PM
>
> Overvolting NST by 25% means usually a serious core
> saturation.That's not a healthy operation mode for any
> transformer.Also,NST can eat a lot of power itself then.I
> bet that your Tesla coil circuit powered by overvolted NST
> does not get more than 500 W out 620 W supplied.I don't know
> what to say about dr. R's paper either.It is more surprising
> that he found small coils so inefficient than large coils
> efficient.My only scrappy coil is a 3" coil,with static
> gaps.340 kHz resonant,with virtually no topload.Power input
> 100 VA.It gives 11 inch sparks (so the spark factor is
> 1.1).I'm positive that many list members can make 100 VA
> coil with at least 1.4 factor.Which is much better than
> according to pro's experience!
> :)
>
> Dex
> --- futuret@xxxxxxx
> wrote:
>
> From: futuret@xxxxxxx
> To: tesla@xxxxxxxxxx
> Cc:
> Subject: Re: [TCML] Toroid question
> Date: Tue, 02 Jun 2009 19:23:11 -0400
>
> Dex,
>
> Yes, the spark lengths decreased for equal power input as I
> increased
> the PPS rate.
> I agree that large bang size is very important. Yes,
> larger coils have
> lower losses,
> and that may account for the better efficiencies of the
> larger coils.
>
> My old research coil using a regular 12/30 NST, drew about
> 620 watts,
> and gave 42" sparks.
> That's how much power they draw when the system is set up
> as mine was.
> I fed
> the NST with 140 volts input... that's part of the key to
> the excess
> power draw. Probably
> some saturation going on at that voltage. Not
> many folks realize they can draw that much power. My
> TT-42 coil is not
> as efficient
> because it was built for portability.
>
> The coils you mentioned for which the factor varied from
> 1.5 to 2....
> I see that as still being
> close to the formula, since the formula is a rough
> guide. I've
> mentioned over
> the years that the factor can be changed for certain coils,
> etc. I
> just used
> 1.7 as a sort of average for various coils. I've seen
> even rather
> small coils
> show a factor of 2.0, such as the solid state DRSSTC
> types.
>
> Regarding the diameter of the secondary, I don't have a lot
> of faith in
> that
> concept. I think smaller diameter coils may often use
> smaller toroids,
> or have
> too few turns of wire, etc. I'd like to do the
> comparison tests
> myself, but
> I haven't gotten around to it. It's true that a
> larger diameter coil
> has
> more inductance for a given number of turns, and will show
> lower
> losses, etc.
> But I don't think it should make a great difference for
> spark length.
> I'm sure it will make some.
> Of course an extremely tall narrow coil would be bad, since
> it would be
> hard to
> couple, and might not have enough inductance, etc. I
> like to think of
> the
> diameter as increasing as the overall coil size increases,
> just to keep
> everything
> in proportion, electrically and all.
>
> Cheers,
> John
>
>
> -----Original Message-----
> From: Dex Dexter <dexterlabs@xxxxxxxxxxx>
> To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
> Sent: Tue, 2 Jun 2009 7:42 am
> Subject: Re: [TCML] Toroid question
>
>
>
> John,
> Thanks for clearing up these doubts.
> I understand it is an empirical formula for how a well
> constructed
> spark gap
> coil should perform aproxinately.You gave an example of 12
> kv/ 30 mA
> NST coil
> with SRG and 120 PPS delivering 38" sparks.I know one can
> even squeeze
> out
> little more juice than 360 W from such NST ,but not
> much.Therefore the
> coil
> outperforms the formula prediction and factor b=1.7 in
> spark lenght =
> b*SQRT(P)
> should be replaced by b=2.
> I'm wondering if you observed a gradual spark lenght
> decrease in your
> tests as
> you changed sync PPS rate from 120 PPS to 240 PPS,and then
> to 480 PPS
> keeping
> the input power same all the time?The efficiency of power
> source unit
> matters
> ,but not much for bigger coils.Also power factors are high
> enough for
> SRG
> systems and folks are right when plugging VA instead of
> W.Speaking of
> larger
> coils,I don't know much data either.Here's what I've found
> out so far:
>
> K.Eldridge's big Oklahoma coil:
> Power input:30 kW
> Break rate:120 PPS SRG
> Bang size:~250 J
> Spark lenght:26-27 ft
>
> M.Denicolai's "Thor":
> Power input:5 kW
> Break rate: 250 PPS,DC charger realisation
> Bang size:~20 J
> Spark lenght:10 ft
>
> G.Leyh's Electrum :
> Power input: 95 kW
> Break rate: 360 PPS,DC charger realisation
> Bang size:266 J
> Spark lenght:~40 ft
>
> Dr. Resonance's Australia coil:
> Power input:~150 kW
> Break rate:120 PPS SRG
> Bang size: ~ 1250 J
> Spark lenght: 78 ft
>
> The only system here which follows well the formula is Thor
> with
> b=1.7.The
> Oklahoma coil has b~1.85 while Electrum has b~1.5.I noticed
> that
> despite much
> higher power level Electrum use aprox the same bang size as
> the
> Oklahoma
> coil,but works at 3x higher PPS rate.Contoversal
> Dr.Resonance's coil
> uses even
> more power,but what differs drastically is a huge
> bang size of it.If
> the data
> is correct that coil has b=2.4.I think bang size means a
> lot.Also it is
> known
> fact that bigger coils with larger diameters tolerate
> higher couplings
> and
> larger bang sizes.I'm not sure if the smaller aspect ratios
> and larger
> diameters
> give the only advantage due to possibilty of higher
> coupling and larger
> bang
> sizes or there's something more to it (unknown to
> me).Here's
> interesting paper
> of Dr. Resonance regarding the role of secondary diameter
> in Tesla
> coil's spark
> performances:
>
> http://www.classictesla.com/download/resonance_tips.pdf
>
>
> Dex
>
>
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
>
>
>
>
> _____________________________________________________________
> Washington DC's Largest FREE Email service. ---> http://www.DCemail.com ---> A Washington Online
> Community Member --->
> http://www.DCpages.com
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
>
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla