Re: SSTC Magnifiers / High Frequency - High Voltagetransformers

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dhmccauley-at-spacecatlighting-dot-com>

 >  > Actually, it is not as difficult as it seems.  Soft ferrite cores
 >  > are readily available in a variety of
 >  > sizes from various manufacturers including ferroxcube, fair-rite,
etc...
 >  > With a large core, voltage stand-off isn't really a problem.  Basically
 >  > U-Cores work extremely well and with using
 >  > a ferrite such as 3C90, 3C91, etc..., efficiency and operation at high
 >  > frequencies (100-300kHz) is good.
 >  > For higher powers, cooling is required as the cores can get fairly hot.
 >
 >  > ------------------------------------
 >
 > 1.  What core # and bobbin assembly are you using?
 > 2.  Where to buy (or get "Engineering Samples"  :^)  )?
 > 3.  One way to build a HV driver would be place primary
 >       on one leg of core and use "segmented" scramble wound
 >       secondary.  This is HV design used on electronic NST's.

I don't have the core model number in front of me, but if you go to
ferroxcubes website (www.ferroxcube-dot-com), and look in their downloadable
handbook
under U-Cores, they have a wide variety to choose from.  I chose my mine
based on running at 200kHz, and about 2000V pk-pk secondary output.
I chose some cores with Ae value of greater than 100mm^3 which are some of
the larger ones.

Yeah, 20kV secondary output *is* quite a lot and voltage stand-off would
defintely be a problem.  Right now my secondary output is only about 2kV,
but I am planning to increase that a bit once I fully test this design.
Even with this step-up transformer, my output is signifcantly greater than
what you saw at the teslathon
this summer.

My goal is to get at least 36" streamers on a continual, reliable basis by
next summers tesla event using only a low voltage input of 120VAC.  I want
to stick
with the lower voltage for reliability as approaching 240VAC, the system
becomes much less reliable.

I'm currently working on some PSPICE simulations of my solid state tesla
coil.  Once I get these nailed down, I will start some serious playing
around with
the models trying out some new and exotic things as well as incorporating
the transformer into the design as well.

http://www.spacecatlighting-dot-com/sstc_pspice.htm

I'll keep you posted.  Thanks

Dan


 > ------------------------------------
 >
 >  >
 >  > My current design utilizes a Ferrox U-Core using 3C91 ferrite core with
 >  > primary at 30 turns, and secondary at 150 turns
 >  > for a 1:5 step-up transformer design.
 >
 >  > ---------------------------------------
 >
 > For Bylund's final bridge design, he was running +/-160VDC bus
 > and was getting about 20kV (pk-pk) out if memory is not failing me...
 > Was pushing 1:16 turns ratio; corona, insulation failure was a
 > major problem.  I believe in final imbodiment, he had to use
 > an oil immersed driver transformer to control dielectric breakdown.
 >
 > Unit could get up to 18" discharges.  Used bipolar transistors with
 > proportional drive (with Baker clamps) -at- 100kHz.  Worked remarkably
 > well considering the "sucky" HV transistors that were available.  I
actually
 > designed (but never built) a half bridge FET unit about same time,
 > thought it would have been simple, it would have detonated many FET's.
 > I thought FET body diode would have been "good enough", had
 > no schottky + HV flyback diodes in the circuit.  Was going to used
 > a SG3526 and Pulse Engineering GDT.
 > -------------------------------------
 >
 >  > Dan
 >
 > Regards
 > Dave Sharpe, TCBOR
 > Chesterfield, VA. USA
 >
 >
 >
 >
 >