My second DRSSTC

[erdal]

Hi Mads,
I could not record the video because I tried inside at the home. It's make very dangerous sparks i just took some photos. I plans to record test videos outdoors

[erdal]

Hi again 

Full power @ 700amps 325 volts in open air tests 
I am planing to changing IGBT’s CM200 to CM300, 600v to 1200v with voltage dublicate

[oneKone]

i don't know how i missed the original build but this is awesome! i love the simple ingenuity behind the ikea desk. it's truly an amazing looking coil   

[erdal]

THNX oneKone
Misson Impossible 700 amps OCD, 340 v bus voltage

When johnny comes marching back home

mmc capacitors fail after long tests 

My new mmc design. each 0.1 uf, 1200 volts, 8 ampers irms,  12 parallel 5 serial total 60 caps. 0.24 uf 6.000 volt 96 amper irms

[Mads Barnkob]

These capacitors are also less sturdy than the CDE 942C series or snubber MKP pulse capacitors, so failure on such a MMC is expected if it does not have a large overhead for voltage and current specification.

Your new MMC layout is problematic, the inner capacitors will not be able to radiate the heat from their losses, so they will heat up faster than the outer ring of caps and will fail before the others due to temperature changing their characteristics.

[Bambinz]

I agree, and then if the inner caps fail the other caps fail consequently (avalanche effect).

[erdal]

Hello All,
Not work!
I changed the MMC, bus voltage ok, driver ok, but nothing any sparks.
Fuse not blown, no any shortcut at IGBTs
what would be the reason?

[erdal]

Hello,
Now working one of IGBT is death. G to E is 155 ohm
I changed CM200DY-12NF to CM300DY-12NF. Can i increase 700 amps to 900 amps at OCD?
Thank you
Erdal

[Mads Barnkob]

I still recommend that you do a Fmax2, switching loss calculation to make sure that the CM300 can withstand 900A at 100 kHz, it is a much higher frequency than CM300 is usually used at. I think the highest recorded I got on my page is 700A at 72 kHz by loneoceans.com

Good to see that you found the defective IGBT brick, how about the gate resistor/zener diode, were they damaged aswell? I often saw this problem when a IGBT died.

[Hydron]

I see that you're using the 600V rated CM300, these should be a lot faster than the 1200V ones, so I suspect that 100kHz/900A will be ok, though at the upper limits of what you can do with them.

[erdal]

I still recommend that you do a Fmax2, switching loss calculation to make sure that the CM300 can withstand 900A at 100 kHz, it is a much higher frequency than CM300 is usually used at. I think the highest recorded I got on my page is 700A at 72 kHz by loneoceans.com

I thought 900 amps was high, I decided not to exceed 700 amps for CM300 s. I plan to reduce the secondary coil by about 80 - 85 kHz.

Good to see that you found the defective IGBT brick, how about the gate resistor/zener diode, were they damaged aswell? I often saw this problem when a IGBT died.

yes, the zeners are dead too

I see that you're using the 600V rated CM300, these should be a lot faster than the 1200V ones, so I suspect that 100kHz/900A will be ok, though at the upper limits of what you can do with them.

Yes, the CM300 is from 600 volts. My bus voltage is 325 volts. if I design a new secondary and lower the frequency, I can try to increase the current

New CM300 test, Metallica Unforgiven

The Final Countdown

[erdal]

Hi,
Here is my new secondary winding. 110 mm dia to 125 mm dia PVC pipe. Winding length 48.5 cm to 53.5 cm. New resonant freq.= 86-87 khz.
New MMC design 15 parallel 5 serial 0.1 uf 1200 volt snubber caps. 0.3 uf, 6000 volt 120 amps IRMS

Working very well

Erdal,

[Mads Barnkob]

Since you wanted to go up in peak current, upgrading your MMC and secondary coil is a wise choice.

Even though the secondary is just making the topload sit 10 cm taller, it will make a difference in regard to avoiding too many strike rail hits.

Your MMC still seems to be a stacked pyramid, how is the capacitors in the middle holding up with temperature after playing MIDI?

Keep sparking!

[erdal]

Hi Mads,

My pyramidal MMC design is not a good idea for inner caps temperature. I use for short time tests, because i found that caps in local stores and they are quite cheap.


The new mmc design will be as follows;

[erdal]

Hello all,

New work at the weekend. first, my final mmc design: 3 serial 14 parallel totally 42 snubber caps with 3D printing saperator. 6.000 volt, 126 amps Irms, 0.466 uf











Second, new topload 54 cm outer dia to 62.5 cm outer dia. New resonant freq ~80 khz. My goal is; 800 amps ocd at cm300-12nfh full bridge





Have a nice sunday
Erdal

[davekni]

What tool/software did you use to calculate your coil inductances and especially coupling factor (from your August 31st 2019 post)?  I hadn't found anything available for coupling factor, so wrote my own.  Would love to compare its results with known tools.

Thank you!

[Mads Barnkob]

Erdal, that is a solid MMC design and snubber capacitors are perfect for MMCs, good that you could find those cheap. There is not a thing to put a finger on

New topload dropping Fres to 80kHz, I would say you could push those CM300 to 1kA if you feel adventurous, you even have a little head room for it on the MMC!

Another thing, all your tinypic pictures have stopped working You should really upload all your pictures directly on the forum, then it will work "forever" and not loose link to some online 3rd party gallery

Davekni, he simulation you see is from JavaTC, the worlds best online Tesla coil calculator, there is a link to it, among other calculators here: https://highvoltageforum.net/index.php?topic=573.0

[erdal]

Hi,

I liked my new mmc design too I spent a little more effort on this design. So what have I learned? The most critical part the Tesla coil is mmc (of course the most likely failure and the most spend money)

A little tips, a long screwdriver is perfect breakout point for tesla. No any corona effect for arround surface. sparks only end of the screwdriver. I tried some materials like copper rod, aluminum rod etc. But none of them had a perfectly polished surface, resulting in a corona effect.

I don't intend to make a larger tesla coil. With this coil I can disturb my neighbors long enough My goal is to push the limits of this size tesla coil

What tool/software did you use to calculate your coil inductances and especially coupling factor (from your August 31st 2019 post)?  I hadn't found anything available for coupling factor, so wrote my own.  Would love to compare its results with known tools.

Thank you!

Mads gave the answer in detail with the link. I use javatc online java based calculator. Its great tool for drsstc. I tested that my measurements and calculations give the same value in real

Thnx,
Erdal