Re: Magnifier conversion - "best" mode?

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

Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>

Hi Antonio,

At 09:59 PM 4/13/2003 -0300, you wrote:
>Tesla list wrote:
> >
> > Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>
> >
> > Hi Antonio,
>...
> > Happily, even with the losses (especially the streamer loading), the values
> > still give very good if not almost perfect C1 to C3 voltage conversion.
>
>In the lower modes, the system is very insensitive to tuning and to
>losses.

I see.  Best to use lower modes then since less can go wrong.  Maybe a 
little more stress here and there but that is something we are good at 
dealing with.

>
> > The concerns I see in actually building one are the high L1 to L2 coupling
> > and the construction of C2.  The coupling may be tricky, but in the small
> > coil case the voltages are not super high so maybe it would not be too bad.
>
>As a last resource, the driver can be immersed in oil.

Yuck!!  Don't want to go there ;-))


> >The spectrum:
> > http://hot-streamer-dot-com/temp/NewMag/0413-07.gif
> > 160kHz and 330kHz.
>
>The voltage over C2 really doesn't have the central resonance frequency
>that appears in C1 and C3.

I just wanted to check the spectrum to be sure the frequencies were within 
the range of polypropylene dielectric materials.  If I saw big 5MHz spikes 
or something like that I would have to use ceramic caps.


> > These are well within the range of a series string of MMC style caps.  Like
> > 45  x  1600V 3.9nF poly caps.  Those caps could withstand "accidents" due
> > to their self healing and one could select more or less caps for fine
> > tuning easily.  Instead of trying to get high current we are not trying to
> > get high voltage.  MMCs would be cheap, easy, and very hard to
> > damage.  Door knobs and other caps would work too since the current is
> > reasonable, but we have so much experience with poly caps and the price is
> > very reasonable...
>
>Yes, a long MMC is a good solution. But construction must be careful,
>because the voltage at the top end is very high, and corona may be a
>serious problem. As in the C2 of my directly coupled magnifier:
>http://www.coe.ufrj.br/~acmq/tesla/567c2.jpg (this failed soon)
>http://www.coe.ufrj.br/~acmq/tesla/mres6c2.jpg (this resisted)

I think you have exceeded the ion inception voltage of the dielectrics 
:o)))  At 300 to 500 volts across a dielectric you will see this 
ionization.  In an MMC, we may put that voltage across 90 layers for maybe 
1kV/layer.  Still above the ionization level, but not enough to degrade the 
dielectrics enough in the time we use them.  There may be corona off sharp 
edges and all that but the energy loss should be very low unless we hard 
arc something.


>The mode fixes the ratio L3/L2 too, so for exact tuning you need taps
>in L2. You could make the coil with precalculated taps for some modes.
>The mode also fixes the ratio C3/C2, so you can use a fixed C2 and
>different top loads, or different C2, or any combination. For a fair
>comparison with a two coils system, C3, L3, and C1 should be kept
>constant.

If L2 is a little space wound, tapping should be easy to do as needed.


>The best in terms of efficienty is 1:2:3, followed by 1:2:5. But
>these result in too problematic (challenging!) constructions.
>The next ones are 2:3:4 and 2:3:6. The modes where the multipliers
>differ by just 1 produce "cleaner" waveforms, and smaller voltages
>over C2.

I will look at these modes now that I have a better idea of the details.

Thanks!

Cheers,

         Terry



>Antonio Carlos M. de Queiroz