Re: Magnifier conversion - "best" mode?

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

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <teslalist-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
 >
 > Original poster: "Terry Fritz" <teslalist-at-qwest-dot-net>
 >
 > Hi Antonio,
 >
 > When I originally did this, I was not using your modes.  This morning I
 > studied up on them.  I tried a 2,3,4 mode since I think Boris said it was a
 > good one ;-)  I used your program to find the values since I have not
 > figured out how to do it with the equations yet.  The program is great!!!
 >...
 > 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.

 > The peak voltage drops to 226 kV with loading.  However, the old model only
 > got to 129kV!!

Consequence of the faster energy transfer.

 > That should give 3X the power to a streamer for a brief instant!!  While
 > the two coil system gives a lower voltage over many cycles, the magnifier
 > gives a much higher voltage over fewer cycles.  This is a significantly
 > different situation with the magnifier and my explain why they are reported
 > to work so well!

The "envelope" of the output waveform rises faster, and there are less
cycles in each envelope cycle. The envelope has also a shape similar to
a squared sinusoid, instead of the absolute value of a sinusoid that
appears in a 4th-order system. The notches are relatively longer.
(These effects are more apparent in higher modes.)

 > 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.

 > C2 would be in a corona ring on top of the secondary and I was thinking of
 > having a bottom toroid on L3 to add to C2 too.  However, E-Tesla6 modeling
 > showed that even a giant toroid (2 feet) 3 inches off the ground only gets
 > to 55pF.  So we need a "real" capacitor for C2.

Yes, but you can try to increase the last multiplier of the mode to
reduce
C2. The voltage over it increases a bit, and L2 too.

 >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.

 > 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 also looked at the fist notch quench and no notch quench cases and it
 > appears the first notch quenching is very desirable.  Better quenching, but
 > higher loss, gaps would do well in this situation.

 > http://hot-streamer-dot-com/temp/NewMag/0413-08.gif

Note the double oscillation and the increase in the voltage over
C2 after the quenching. The energy transfer between C2 and C3
is almost perfect in the oscillations. This may deserve some
exploration, as some modes appear to be better in this aspect.

 > http://hot-streamer-dot-com/temp/NewMag/0413-09.gif

The triple oscillation proceeds.

 > So it appears that I can make the magnifier to match many of the
 > modes.  The one I studied above and yours below all seem reasonable.  Do
 > you have any idea if one would be better???  I could do almost any of them
 > so I should try to pick the "best" if there is one.  With the coupling and
 > C2 variable, I may be able to tune multiple modes but adjusting L2 is
 > probably hard.

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.

 > Your modes here have lower coupling and it is very easy to make C2 a higher
 > value but lower voltage.  C2 current is certainly no problem in any case.
 >
 > I need to may C3 a larger toroid since my present one is just too small for
 > the coil.  C3 may end up about 25pF but that should not change things much.

I arranged the equations in my program so you fix L3, C1, and C3.
The driver and C2 are then calculated. So, for different modes
all that you need is a conventional adjustable L1, an L2 with
precalculated taps, and an adjustable C2. The right value for
the lumped part of C2 may be determined experimentally at low
power, by looking at the waveforms that appear when the gap
is replaced by a low-frequency, low-impedance, square wave
generator.

 > I hope to have a magnifier and conventional coil that can be compared
 > directly.
 >
 > Any thoughts on the "best" mode to shoot for are more than welcome!

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.

Antonio Carlos M. de Queiroz