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Re: [TCML] Series Transformers
I have already built a sucker gap, and it seemed to do a decent job
quenching. This of course was with a .013 mfd cap. I suppose when the full
1mfd + cap is hooked up the quenching will worsen? Why do you say a rotary
gap is probably not advisable, electrode spacing has to be too close for
comfort?
On Wed, Jun 18, 2008 at 6:41 AM, Lau, Gary <Gary.Lau@xxxxxx> wrote:
> 2970V @800mA will be challenging. Despite many who thought 4kV is too low
> for a coil, I built a very efficient coil using a 4kV/20mA NST, using a
> single static cylinder gap. While it may be possible to get a static gap to
> work at 2970V, the 800mA part may be difficult to quench. At that low a
> voltage, an RSG is probably not advisable. You would also need a very large
> cap to utilize the full potential of that power supply.
>
> Regards, Gary Lau
> MA, USA
>
> > -----Original Message-----
> > From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> > Behalf Of Phillip Slawinski
> > Sent: Tuesday, June 17, 2008 9:21 PM
> > To: Tesla Coil Mailing List
> > Subject: Re: [TCML] Series Transformers
> >
> > I have a nice variac 20A rated and 0-270V output with 120V in. I was
> able
> > to wire them in series and ran them up to 2970V @ 800mA. Is 2970V too
> low
> > to run a TC efficiently?
> >
> > On Tue, Jun 17, 2008 at 5:13 PM, David Speck <Dave@xxxxxxxxxxxxxxxx>
> wrote:
> >
> > > OK, Phil,
> > >
> > > Looks to me like you want to step 110 VAC to perhaps 1100 VAC.
> > >
> > > If they are identical transformers, then their internal polarities are
> > > probably the same. (But you can't count on that!)
> > >
> > > Wire the two primaries in parallel. Connect the high voltage output
> end of
> > > one transformer secondary to the low voltage end of the other
> secondary.
> > > Power up the pair with a Variac set on a very low voltage, say one
> volt.
> > > Measure the voltage from the low end of the first transformer
> secondary to
> > > the high end of the second transformer secondary. If you have the
> > > connection right, then you should see something like 11 volts. You can
> then
> > > crank up the Variac voltage slowly to confirm that you see a
> corresponding
> > > increase in the output voltage at the high end. Remember that Variacs
> do
> > > not provide any line isolation, and even at a one volt output, the
> "hot" end
> > > of the Variac output is still at line potential and can deliver a
> lethal
> > > shock.
> > > If you don't see any voltage, check the output across each of the
> > > transformers, to make sure that one of them is not open. If both are
> > > putting out about 5.5 volts individually, then you have the secondaries
> > > connected wrong. Just swap the link between the two secondaries to the
> > > opposite secondary pin on one transformer (with the power off!) and
> recheck.
> > >
> > > A small word of warning -- many digital voltmeters (both cheap and
> > > expensive) can give spurious readings when used to measure unloaded
> > > transformers. You may get much more sensible readings if you parallel
> a 1K
> > > to 10K ohm power resistor across the inputs to your voltmeter. I once
> > > wasted a half a day trying to figure out the transformer of a bandsaw
> blade
> > > welder with a good Fluke DVM. The readings were all over the map, and
> often
> > > inconsistent and unrepeatable. Putting a load resistor on the meter
> made
> > > everything work out sensibly.
> > > 1100 VAC isn't going to help you a lot for TC work. You might be able
> to
> > > get away with seriesing 4 transformers for 2200 volts, but at this
> point,
> > > you will begin to stress the insulation between the windings and the
> cores.
> > > I've read of 4 and 6 MOT series strings, but the outer transformers on
> the
> > > 6 MOT strings had to be run under transformer oil to prevent winding to
> core
> > > voltage breakdown. OTOH, the power output of a 6 MOT string (~12 KVAC
> at
> > > 500 mA, if you use big MOTs), can compare favorably with a 5 KVA pole
> pig,
> > > just not so nice and compact, but nearly free, if you can find the
> MOTs.
> > > HTH,
> > > Dave
> > >
> > >
> > > Phillip Slawinski wrote:
> > >
> > >> Step Down transformers run in reverse. The transformers have taps for
> > >> neutral 100V 110V on the primary. On the secondary neutral 420 480
> 550.
> > >>
> > >> On Tue, Jun 17, 2008 at 1:39 PM, David Speck <Dave@xxxxxxxxxxxxxxxx>
> > >> wrote:
> > >>
> > >>
> > >>
> > >>> Phil:
> > >>>
> > >>> What kind of transformers?
> > >>>
> > >>> You can't series NSTs, 'cause they are center tap grounded. You can
> > >>> parallel them for more current, though.
> > >>>
> > >>> Dave
> > >>>
> > >>> Phillip Slawinski wrote:
> > >>>
> > >>>
> > >>>
> > >>>> Does anyone know of a way to wire two transformers so that they are
> > >>>> oppositely phased?
> > >>>>
> > >>>
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