teravolt wrote ...

Hi Austin before you spend around 700$ for a large DRSSTC I recomend DR. Gigiavolts DRSSTC book



I hate to plug it but it it is one of the best descriptions of a DRSSTC I've read. the contents will be true for any DRSSTC. One of the diferances that the book won't talk about is the cm600 some of the most advanced work done with the cm600 has been done by Finn Hammer at



if you want determin the rateing if MMC go by the dc rating and peak voltage at the primary. RMS is a method for giving AC volts a DC equivalent and visavesa ie. in capacitors if you have one with 1000vdc rating you can not use it on a AC circuit of any more than 707vac because you would excied the voltage rateings of the cap. The reson for this that the peak of a signwave at 90, 270 deg. of a 707vac signwave is 1000vp. The formula for this VRMS=sin45*vp=.707*1000=707vac RMS. RMS is just a convension for dc equivalent. If you expect to see 10000Vp over the caps you will only need 5+ 2 or 3 extra in your strings will give you over voltage pertection not 12 deep. have a look on finn's Hammertone "Predikter", hear he is using 3 strings of 6 and getting 5' sparks and even less caps in this video



what makes the polypropalene caps one of the best types for teslas to use is because of there low ESR equivalent series resistance and high di/dt rateing. The reson this important is because as Steve McConner put it at resonance XL and XC cancel out and what you are left over with is the resistance of your primary inductor restance ie. refigerator tubing and the ESR in your cap bank in series with each other. Your source voltage ie. your doubler of +- 340dc divided by the resistance in the last senance plus the resistance in your igbt and doubler will be the current flow through everything at each switching. it looks like this V/R=I so Vcharge/R'dubler+ R'igbt+ R'cap+ R'indutor=primary current. this current times your XL or XC witch is the same at resonance will be your primary voltage across your caps. Some of thease values like esr can be found in the manufacture's data sheets. The currents that are projected hear are in the couple thousand amp range. Your model is only a guide line and nobody hear can tell you exactly how it will come out when it is biult and it may take alot of mesured analisis and help from others to get it going with your levle of understanding. do you have a oscilloscope,dmm,function generator,L-C meter? Steve McConner is the only one who has brought up frequency splitting. After its set up, you will need to tune your secondary frequency a little high to compansate for the detuning as the arc sets out from the tesla. as the arc sets out I have read hear that it is about 1pf for one ft. of arc

about the cm600s they have lots of delay and your control circuit may have to compinsate for troughput delay if your electronics and dead time. read and let us know what you come up with

teravolt wrote ...

hello Angstrom, in this pdf for the cm600 there is no acual number for on resistance because it is a dynamic number. In the graph called "output characteristics" it will give the C-E voltage drop at any particular current through the device so at 1200 amps there will be 12v across the CE junction or 10m ohms and goes to 20m ohms at around 400A. thease values happen when the gate is at a full 20v.

the esr for electrolytics and the poly snubber caps also have a factory number in the milli ohms. Roughly after you add it up you will be under half an ohm. what it may be in the end after it is built you can find out with a ac current probe and oscilloscope

if Austin built a full bridge he would put twice the voltage in to his primary from his doubler at the full 675v and nearly twice the output from his tesla. He also would need to duble his MMC voltage. To get any meaningfull information he will have to mix mesured numbers with his calculations. maby others can coment but moast seasond coilers have a set of guide lines based on there expierience and under stand what there materials can do. In big teslas I find that the manufacurers specifcations are far excieded

SteveC wrote ...

How is your design process coming along Austin? Do you have a variac to power this coil?

Angstrom wrote ...


I know this... but the cap still has this characteristic impedance (even though it cancels when the tank circuit is at resonance), and you use this impedance to calculate the DC rating of the cap. Right? That is all I am wanting to confirm here...

I would LOVE it if I were wrong... this method always seems to yield very high voltages (and therefore very expensive MMCs). Yet some DRSSTCs go a bit lower than this. And they most certainly don't go as high as 15kVDC rating.

Angstrom wrote ...

I am pretty confident that you only need to use the reactance of the cap to calculate it's voltage rating... and you are fine using the DC rating as long as you give it plenty of headroom (I think at least 1.41*DC value, preferably a bit extra). I was told this by the designer of ArcAttack's coils, and they recently ran the coils in shows for an entire month straight (7 days a week) and the only failure was a circuit breaker.