Re: An SSTC simulation

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

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]