Re: An SSTC simulation

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

Original poster: jimmy hynes <chunkyboy86-at-yahoo-dot-com> 

You don't really have to build 6 of the dual driver/crossover control 
circuits. You could use a
gate drive transformer with 6 secondaries, or use big IGBTs, so you don't 
have to parallel them.
You could also connect to the emitter through a 0.1 ohm resistor or 
something. The voltage should
be pretty close, so the resistors should stay cool, and the current should 
share well.
--- Tesla list <tesla-at-pupman-dot-com> wrote:
 > Original poster: Kchdlh-at-aol-dot-com
 >
 > 1.  The C8 voltage is 90 deg. out of phase with respect to the secondary
 > voltage.  C8 is, of course, the resonating capacitor rather than the
 > energy-storage capacitor; those are C4 & C7.
 >
 > 2.  The frequency is determined by my already-constructed secondary.  The
 > coupling coefficient I just picked out of the air; I can change it at will
 > in the simulation.
 >
 > 3.  If I actually get to building this I'll probably use IGBTs.  Partly so
 > I won't have to bother with Shottkys in series.
 >
 > 4.  The storage capacitors are the key to success: not too many (if any!)
 > will be expected to stand prolonged full-charge/full discharge at
 > 60/second.  I've queried Electrocube about their motor-run capacitors but
 > no response yet.
 >
 > In addition to repeating my comment that one would not need EX-OR U1, I'll
 > mention here that a mains-zero-crossing gate circuit should be added.  With
 > too much gain in E1, I found that oscillation tends to prolong so that
 > deleterious recharging of C4 or C7 will occur during the following 1/2
 > mains cycle.  You want to cut that off at 1-2 ms.  I've used another EX-OR
 > as a conventional pulse-generator running off the voltage across D5 and
 > operating a clamp-to-ground across D6/D7.
 >
 > I'll mention something else:  I now more fully realize that in any "totem
 > pole" power-transistor scheme using like-transistors (both N or both P),
 > and where you want to do as Terry Fritz has suggested in using multiple
 > resonating capacitors for paralleling the "totem poles", you have a problem
 > with driving all the "top" transistors--the ones with floating
 > sources.  Each has to be driven separately.  So...in my scheme, I'll have
 > to have 6 of the dual driver/crossover control circuits.  A bit of a
 > vexation but it can't be helped.
 >
 > Ken Herrick
 >
 >
 >
 > In a message dated 11/9/03 12:00:52 PM Pacific Standard Time,
 > tesla-at-pupman-dot-com writes:
 >
 >
 > >Subj:Re: An SSTC simulation
 > >Date:11/9/03 12:00:52 PM Pacific Standard Time
 > >From:<mailto:tesla-at-pupman-dot-com>tesla-at-pupman-dot-com
 > >To:<mailto:tesla-at-pupman-dot-com>tesla-at-pupman-dot-com
 > >Sent from the Internet
 > >
 > >
 > >
 > >Original poster: a a <hermantoothrot2000-at-yahoo-dot-com>
 > >
 > >Hi,
 > >
 > >In your simulations, does the voltage across C8 drop back to zero at the
 > >secondary voltage peak?
 > >
 > >I had thought about discharging the capacitor, but decided against it
 > >because the current it would have to withstand. You could get away with
 > >much less energy storage, which is good, but the rms current would be too
 > >high. In my current design, you can keep adding capacitors in parrallel, so
 > >even cruddy capacitors will work if you have enough.
 > >
 > >Right now I have 40 1000uf 200v (10000uf 400v) capacitors for energy
 > >storage, but I think they may be the limiting factor in my design.
 > >
 > >The average driving voltage is also less, so you need a little more current
 > >for the same power, but that is a minor point.
 > >
 > >I had also thought about dynamic tuning, but decided against it because of
 > >simplicity. It is very easy to manually find the resonant frequency if you
 > >are using an oscilloscope while it is running, but I don't know if you can
 > >do it otherwise. You still have to mess around with the tap point on the
 > >primary to get the right tuning there.
 > >
 > >Why such a high coupling and high frequency? You can get away with more
 > >transfer time, and it is easier on your MOSFETs. I used 8 cycles (K~0.12)
 > >at 60khz, and still got some pretty good results. I think IGBTs would be a
 > >better choice for this too. One IRG4PC40W would be better than your 6
 > >MOSFETs at any current above 35amps.
 > >
 > >If you find some capacitors that can stand completely discharging 60 times
 > >a second, then it would probably be a better way of doing things.
 > >
 > >[snipped]
 >
 >


=====
Jimmy