Kaizer DRSSTC II

Introduction

I wanted to build a small DRSSTC in a few days without having prepared anything, most parts are reused or scrapped from things I have found and saved.

 

Safety

WARNING!: Working with electricity is dangerous, all information found on my site is for educational purpose and I accept no responsibility for others actions using the information found on this site.

Read this document about safety! http://www.pupman.com/safety.htm

 

Considerations

I was nervous that the metal enclosure for the driver was too close to the primary coil and would absorb some of the energy, first tests show no sign of heating of the metal.

I made the bridge section entirely on a normal one sided PCB and was not too sure if the traces were thick enough to withstand the high peak currents or keep a low inductance layout. It all seems to work without problems.

 

Specifications

  Revision 1 Revision 2
Bridge 2x G12N60C3D IGBTs in a half bridge configuration 2x IXGN60N60C2D1 IGBTs in a half bridge configuration
Bridge supply 0 – 160VAC through a variac, 6A rectifier bridge and 2x Aerovox 410uF 430V filtering capacitors in parallel.  0 – 210VAC
Primary coil Flat primary. Inner diameter 70 mm, Outer diameter 187,36 mm. 6 turns 1,78 mm copper wire (2,5 mm²), turn spacing 8 mm. Tapped at 4.8 turns.  
MMC 2 in series Cornell Dubilier (CDE) 942C20P15K-F capacitors for 0.075uF at 4000VDC rating.  
Secondary coil 50 mm diameter, 200 mm long, 1430 windings, 0,127 mm enamelled copper wire.  
Resonant frequency Around 327 kHz.  
Topload 40 x 215 mm aluminium tape on a Styrofoam toroid.  
Input power 250BPS, 250uS on-time, 68 primary cycles, 300A limiter: 120VAC in.  350BPS, 120uS on-time, 35 primary cycles, 280A limiter: 210 VAC in at 2A. 420 Watt.
Spark length Up to 240 mm long sparks.  Up to 370 mm long sparks.

 

Schematic

The driver is a variation of Steve Wards universal driver and beneath you can see the bridge schematics.

 

Construction

13th August 2011

Optimize driver PCB, design bridge PCB, toner transfer to PCB.

14th August 2011

Etch PCBs, assemble bridge PCB completely, half done with driver assembly. Heat sinks, electrolytic capacitors, voltage splitting capacitors and rectifier bridge are all salvaged components. Materials for building a enclosure and base is found. Lexan salvaged from LCD monitors is used for the base and some normal house wiring is used for the primary coil.

 

15th August 2011

Winding CTs for feedback and OCD, building enclosure and base, driver PCB assembled.

 

16th August 2011

Driver PCB fault finding and testing, enclosure and base building. I had forgot to add the trace that resets the OCD on the driver board after I moved it while optimizing the board layout.

 

17th August 2011

Complete construction and ran first test, no first light.

Some more detailed pictures of topload, secondary with terminations and primary coil.

Flat primary. Inner diameter 70 mm, Outer diameter 187,36 mm. 6 turns 1,78 mm copper wire (2,5 mm²), turn spacing 8 mm.

50 mm diameter, 200 mm long, 1430 windings, 0,127 mm enamelled copper wire.

40 x 215 mm aluminium tape on a Styrofoam toroid.

 

28th August 2011

First light, phasing of feedback transformer was wrong.

3rd September 2011

24 cm sparks, running 250uS, 68 primary cycles, 120VAC in, 268A primary current. 250BPS.

 

Here is a scope shot of the primary current waveform and a zoom of the same.

 

4th September 2011

I blew up both IGBT transistors running at the same settings as above on the 3rd September 2011, but at 160VAC input, nothing violent, just a flash and all was silent.

I will rebuild the bridge with IXYS IXGN60N60C2D1 IGBTs, which will hopefully make the bridge indestructible compared to the size of this Tesla coil.

11th September 2011

Rebuild the bridge and spent the day fault finding on the circuits as it did not work, turned out to be a 33V Zener diode on the bridge board that was short circuited.

 

16th September 2011

I recorded some data from different settings and came up with following before admitting that my heat sink is just too small. Further tuning is till needed, I hope it can do better and it seems to never go higher than 280A primary current.

I peak Voltage in, AC Current in, AC Burst length BPS Watt, AC Spark length, mm
280 210 0,5 120 200 105 274
280 210 0,75 120 300 157,5 290
280 210 2 120 350 420 354
280 210 4 120 500 840 370

200 BPS, 274 mm sparks.

 

350 BPS, 354 mm sparks.

 

500 BPS, 370 mm sparks.

 

Here is the current waveform which pretty much stayed the same doing these tests, also a better quality picture of the sparks.

 

Additional tuning gave me much better results in the form of almost the same spark output at lower on time, lower peak current and lower power in.

Here it is a screenshot of a spark going out to 337 mm running 70uS on-time, 260A peak current, 300 – 400 BPS at 260VAC at 0.5A.

 

Conclusion

Revision 1

It is no problem building a small DRSSTC in a few days with some previous knowledge and a off the shelf secondary coil.

In the future I will properly not make another Tesla coil with TO-247 IGBTs, I need some more overhead with the way I push my Tesla coils.

 

Demonstration

28th August 2011

First light

 

3rd September 2011

Came out a bit dark, but shows 24 cm sparks, running 250uS, 68 primary cycles, 120VAC in, 268A primary current. 250BPS.

 

16th September 2011

37 cm sparks, running 120uS, 35 primary cycles, 210VAC in, 280A primary current. 200 – 400 BPS.

 

16th September 2011

33,7 cm sparks, running 70uS, 260VAC in, 260A primary current. 300 – 400 BPS.

14th February 2012

Playing Doom 1 – Episode 1 soundtrack with my new midi modulator.

111 thoughts on “Kaizer DRSSTC II

  1. hey, i want to build a similar coil using this driver, can you send me either schematics, eagle files, a board transparency, or all of the above? all i realy need is a black and white layout and a parts list, but i will take anything you can provide.
    thanks-
    ben

  2. Hey Ben,

    The driver is almost a copy of Steve Wards universal driver, you can find it on his website. The board layout is a constant improving work flow which currently have some hacks and bugs, so its not public.
    Stewe Ward got all you ask for online at his website, just google for it.

    Kind regards
    Mads

  3. Nice work.

    Could you please explain your scope setup for the picture? Where you measuring? Differential and displaying a math trace.

  4. Hey Adam

    I am measuring primary current with a Pearson current monitor model 110. It is a 5000 A monitor giving a 0.1 V/A into 50 Ohm. My oscilloscope is adjusted so it shows 1V/A.

    Kind regards
    Mads

  5. mann, i have questions,
    which primary coil is the best for little DRSSTC’s? vertical, flat or conical? a feedback CT in secondary’s base is safe?
    thank youu!
    i have a small 35cm arcs drsstc but sometimes it go to fail :/

  6. Hey 08Kutt

    I would prefer the flat primary to get a greater distance between the topload and earth rail, you will likely get racing sparks from high coupling with a vertical primary and strikes from topload to the earth rail.

    I only use primary feedback as it provides feedback from the circuit that you control and you can run the inverter part without a secondary coil in, but use a dummy load of metal or water in a pan.

    Kind regards
    Mads

  7. HI really nice set up,liking the sound on your new midi modulator,any chance you could forward me the schimatic,mine sound dire compared to yours!!
    thanks

    Markznsparkz

  8. Hey M Griffin

    I bought the midi controller from one of the guys on 4hv, I do not have the schematics or microcontroller code 🙂

    Kind regards
    Mads

  9. Hi
    Can you please tell whitch type of ferrite core Can i use for feedback and ocd , is it need to be type 77 or Can i use cheap one from ebay?
    Thanks

  10. Hey Dario

    You can use type 77, just be sure to buy some with a permability over 4000. Avoid the cheap ones from ebay! I have also used N30 material with permability between 3900 to 6000. Just be sure to get some cores with a large enough cross section, then it should all work out great for you.

    Kind regards
    Mads

  11. Thanks for repply.
    i am stil trying to get all components for building,so i was wondering i your opinion whitch IGBT would you pick for the setup of small DRSSTC ,secondary will be 90mm x 20-25 cm and powering from 240V , Bus capacitor 2200uf 450VDC i was thinking og IGBT brick IXGN60N60 but maybe it could go with smaller one?
    You preffer flat primary or?
    Thanks
    Dario

  12. Hey Dario

    Use the IXGN60N60 so that you have some head room, it is the most fun when it is not the electronics that is the limit to spark length, but the floor and ceiling 😉

    I prefer flat, not as tight coupling and it is further away from the topload, fewer strikes close to the primary, you could also avoid raising sparks with the lower coupling.

    Kind regards
    Mads

  13. Hi Mads
    i found 500T600-3E2A ferrite that i used for old project i think they will be ok for GDT and feedback,ocd ..,only i am not surre is the center hole 25mm to big for cable 10-16 mm2 since is small DRSSTC otherwise please comment the core.
    Thanks
    Dario

  14. Hey Dario

    The cores seems to be rated for 5000u, which is sufficient.

    The center hole is not too big, it will be fine and you have some space for extra insulation.

    Kind regards
    Mads

  15. Hi ILoveStorms

    For a small DRSSTC like this you can use almost any polypropylene switching capacitor with dv/dt around 1000 and 250-500Apeak, or even less if you can accept some losses in the tank capacitor. The 940C/941C are virtually identical and the MKP is the worst of those three. Consider then 942C series as those capacitors are thoroughly tested in DRSSTCs.

    I advise you on using the universal driver to have over-current detection, without it you risk blowing up those IGBTs. They are only rated for 180Apulsed and will likely blow up if you push them beyond 300-400A.

    The Epcos ring core is fine.

    I suggest that you figure out your primary current that you want to run, look at other coils people have made and work out from those figures. The choose a IGBT that can actually run at those peak currents, use a driver with over-current detection to protect your IGBTs from failure. Use my MMC calculator to make a MMC with voltage, peak current and rms current ratings that can withstand your design.

    Kind regards
    Mads

  16. Hey. Those igbts would work then! FGH75N60UF (I’ve read about them being pushed to 450A pulsed)
    And.. Do you have any eagle files for the UD? Also. Can you estimate a cost of the full UD?
    Can the entire thing ( Half bridge , Control circuit ) be fitted in a single board that won’t look ridiculous against the 4 inch wide , 4 inch long mini coil?

  17. Hey ILoveStorms

    I only have ExpressPCB board files for single sided board, not currently public. The parts for UD1.3 driver, without opto receiver is around 14 Euro, that price is when I bought parts for 20 drivers.

    I see no reason why you should not be able to get it all on a two 4×4″ board, have them on top of each other to save foot print, you just have to spend some nights routing till it fits.

    Kind regards
    Mads

  18. One final question.
    It gets me wondering. How is the interrupter connected to the actual control circuit?
    On a side note. What do you think of the IGBT i linked to last post? It seemed to be enough
    On an unrelated side note. Happy christmas
    On a completely unrelated side note. 365 days ago. The world ended
    Happy holidays

  19. The interrupter output goes into a opto transmitter, through a optic fibre wire and into the opto receiver on the driver. This insures total isolation between the Tesla coil and the user holding the interrupter in the hand.

    If you have experience from others that have pushed those to around 500A, they should be fine, as you can see this little DRSSTC runs at about 300A.

    Merry Christmas 🙂

  20. Correct, if you do not need the interrupter signal inverted, skip the first hex-inverter gate, it is only there because Ward used a opto receiver that inverted the signal.

    When you switch currents of these magnitudes, you want control in order to protect your components, if you go for a simpler circuit, you also loose control and accept the increased risk of blowing up your IGBTs.

    The SOT-227 IGBT die sizes are about the same as the TO-247 so they only have slightly better ratings and does not handle currents much over their Icm rating as the increased Icm rating is due to the larger heat sink foot print. Go for a maximum of 500Apeak with that IGBT.

    You can just add external ultra-fast diodes when there are no internal diodes.

    Kind regards
    Mads

  21. To ILoveStorms
    it might be werth you looking at the onetesla design there was someone on ebay selling the PCB for £20 i made one from this and they work very well with minimal effort in building ,mine can produce a good 2ft arc with steve wards interupter,but like it has been said a coil that is too short will just arc out to ground or worse to the primary blowing the power out,the main thing you need to know when tunning it is to make the primary lower in frequency than the secondery as the secondery frequency will drop as the arcs are formed the longer the arc the more the frequency drop.mine has about 15 to 20 % drop at full power,i blew a lot of igbts untill i worked this out.

    http://onetesla.com/

    here is a video of mine.

    http://www.youtube.com/watch?v=YKd7rl0bQps

    it gives basic dimetions under video

  22. So far you went from using a Icm 180A TO-247 IGBT to a half bridge module.

    Your idea of using only two capacitors is simply inadequate to such a bridge size.

    The secondary coil is in my opinion too short and you will regret trying to wind such a thin wire.

    There is no way you can use a fuse to catch a over-current 100A larger than 500A when the burst last for 200uS.

    If you want a simpler driver, make a hybrid between the simple dual driver antenna feedback driver and Wards UD1.3. But as I said earlier, it is a compromise between cost, complexity and willingness to risk blowing stuff up.

    I think you should replicate the dimensions of a existing DRSSTC and learn your way around it, you have many basic questions that show you do not fully understand the mysterious ways of amateur coiling, I am no expert, but I learned it slowly and by trying what others did first, just like you learn anything in school. There is no short cuts, there is no simple or cheap way to reliably make long sparks.

    If something is worth doing, it is worth doing right.

  23. I usually point the break out point up.
    On the one tesla site. In the downloads section.. When i try to download the eagle files it gives me 404 Not Found.. And i think a strike rail would fix that problem :). By the way. Your coil looks amazing :D. A spun topload would make it look perfect.

    Mads
    Have a peek at this http://www.loneoceans.com/labs/drsstc1/
    It uses 36 AWG wire.
    I already have a hard time winding 34AWG wire.
    So i re-adjusted the secondary coil to my liking.
    Measured in inches

    Diameter : 4
    Length : 10
    Turns : 1587
    AWG : 34
    Toroid : 10 inch major diameter , 3 inch minor diameter

    Primary:
    Form diameter : 6
    Form height : 1.6
    Turns : 3.1
    AWG : 12 (Wikipedia says it has a rating of 5.3 KA for 32 MS)

    What JAVATC spat at me when i gave it the values
    http://i1331.photobucket.com/albums/w591/grim3322/output_zpsc6a4ee28.jpg
    The IGBTs will be the FGH75N60UF
    And two 1 UF 2KV caps in series
    Thank you
    Merry christmas!

  24. you can get the onetesla eagle files from here.
    http://isopack.blogspot.co.uk/2012/05/onetesla.html

    if you still have problems i can send you a copy on email.

    toploades are way out of my price range but i do agree it would look better and proberbly get a slightly longer arc.

    you don`t want to let the arc hit a strike rail or any earth if it can be helped ,strike rails are only there to stop the arc from hitting the primary but in hitting the rail or another earth i causes the current in the primary to go up and can blow the igbts this is why the more elaboate coils have current limiters that wind back the interupter input as soon as it detects a over rise in the current which is set by the user.

  25. A quick search on google got me the schematics for 220V
    But. They seem to be shorted O.O http://i1331.photobucket.com/albums/w591/grim3322/Weirdboard_zpsbda40c0a.jpg
    As you can see the main power traces are shorted o.o.. Also the positive lead on the upper capacitor is left unconnected? Same for the negative lead of the bottom capacitor. And two diodes are left unconnected O.O…. And traces from the control circuits intersect with traces from the H-Bridge. The middle pin of the IGBT is left untouched. And what are those dots all around the bridge?

  26. this is only showing half the board the high voltage side all the control chips and drivers are to the left (not seen in picture)the dots is the copper track on the other side that carries the main power from the 1000uf caps to the igbts.the diodes are connected on the other side.look at the 220v schimatic on the onetesla site.

  27. I am talking about the board files not the schematics. And that picture was something i snipped off the real board files which i have. And is the one tesla board a double sided board? It does not seem to be so

  28. Oh.. I ‘ve never made double sided boards before.. Where are the eagle files for the other side?

  29. The OneTesla is such a simple schematic, you could have drawn your own single sided board by now in ExpressPCB, laser printed, toner transferred, etched and start soldering 🙂

  30. 155 kHz is a good low resonant frequency, the IGBT module is properly over kill compared to the energy transfer possible to the secondary, but then again, you wont blow it up.

    Take a look at your coupling, it is much higher than suggested by JAVATC and for a DRSSTC you do not want a higher coupling than the suggested, the peak current is high enough for transferring the energy and with a too tight coupling you risk racing sparks or flash over. You could also consider making a pan cake coil instead of the helical, pan cake coils have lower coupling.

    I still think you should invest more money in your MMC, did you plot the numbers into my MMC calculator to see if you are within live driving conditions in regard to voltage rating, peak and rms current rating?

    I still think you should use UD1.3 with a proper primary current feedback and over current protection. The antenna feedback and no protection is asking for trouble 😉

    Kind regards
    Mads

  31. I totally forgot the MMC calculator! (Stupid me)
    Throwing the MMC i was planning for at it gave me unsatisfying results. So i redesigned it! The new MMC will sport 4 of those http://www.farnell.com/datasheets/621879.pdf (2KV .68UF ones)
    2 in series and 2 in parallel
    (That is for 300 peak amps and 200 US and 200 BPS)
    The capacitor’s capability is 1026A
    The calculator says that the RMS currents will be 30A , The capacitor’s capability is 31.6 Amps
    Seems enough 🙂
    The FGH75N60UF are not modules. But they seem enough. (They are TO-247)

    A pancake primary.. I might consider it. But i though it was a very good idea to put a large tube (Maybe 4.5 or 5 inches)
    and then wind the primary on it.
    The one tesla schematic is not based on antenna feedback. It seems to have a current transformer
    My reply to no protection is using parts that are more than capable of doing the job. Remember. It is a small DRSSTC just for testing and gaining knowledge i lack
    Also i will go for the double sided PCB. As i want to know how to make those ( I will most probably need it when i try to make the UD)

    And..
    A very merry christmas to you!

  32. Looks good on the specifications so far, as the peak currents are still relatively small in a DRSSTC scale, it should do fine and the MMC only experience a little heating on long run times. Does it also withstand the voltage? We are already using their DC voltage rating as AC voltage rating, so do not have a MMC without voltage head margin.

    Have fun building your Tesla coil and I look forward to see it running 🙂

    Kind regards
    Mads

  33. The coil will only get 220VAC in. That was about 300-310 VDC.. So it seems enough.
    Also i decided on this IGBT http://docs-europe.electrocomponents.com/webdocs/122f/0900766b8122f8a9.pdf
    It has a pulsed current greater than 300A. The difference in switching time is not huge , It uses newer technology AND I do not like pushing anything beyond it’s rating Also i have a Boomophobia (LOL)
    I will begin construction in january.
    Wish me luck!
    Merry christmas

  34. The voltage over the MMC have nothing to do with the input voltage, but the MMC impedance times the primary peak current. Look at the formulas beneath the MMC calculator and try to play around a little with the peak current in the calculator, remember to enter the correct specifications for the capacitor you are using.

  35. I did. And i came up with something. Entering the specifications of my capacitors and coil. I found that the results would be much better if all the 4 capacitors would be in parallel
    That would reduce primary impedance and the peak currents for the capacitors would be ~2000 amps. And at 200 US On time and 200 BPS. It would take 63 amps of RMS currents. RMS currents are about 50 if the peak currents are 500 AMPs ( My tiny coil will probably never get close to that)
    4 capacitors in parallel then.

    Also i though of an idea for a toroid :o. Its similar to Eric goodchild’s largest DRSSTC. Basically i have a ton of 3mm thick zinc coated aluminum wire. Now imagine 4 wood circles each with a diameter of 3.25 inches. Each two will be epoxied to two ends of a wooden stick. So now we have two wooden stick each with a wooden circle on each side. Now we epoxy the sticks together taking care that all the circles are vertical. And then i would drill holes 3mm wide all 360 degrees (Taking care they are atleast 1mm apart. ) And then i would insert the wire Into the holes of all the circles which would form a kind of spiral / winding. The distance of 1mm between wires would make that toroid have a good capacitance. And a wire can be soldered ( From the inside) to connect the beginning and the ending of the coil to cancel the inductance.
    What do you think? In my imagination the toroid looks amazing 😀

  36. The idea of making a toroid topload from wire is far from new, chicken fence was used by some of the old pioneers when making large toroids.

    Try simulating in JAVATC a toroid the size you want to make the toroid and then try with maybe 7 or 9 rings around the outer 180 degrees of the circle. You will see that the capacitance is almost identical, you do not need to have the wires so close and all 360 degrees around, the inside can be omitted.

    The holes you wanted to drill in the circles, make them slits instead where you can insert the wire from the outside and not pull it through, if you have to pull it through 4×15 holes it will look horrible and take forever to do 🙂

    Kind regards
    Mads

  37. The rings must be connected though otherwise they will just arc to each other.. Also the wire.. Is just a wire. Not a tube like they used in that monster DRSSTC. And only 7 rings of the 3mm
    wire would look really empty with a topload that is supposed to be 3 inches high. I eventually though of the idea of the slits though. And pulling the wire through the hole also did not seem like a really good idea 😛

    Also i lack an Oscilloscope so calculations are really my only real way to figure frequencies etc. 🙁

  38. Of course they will have to be connected. What I am saying is that there is no reason, besides purely cosmetic, to add enough rings for it look like a complete toroid as the capacitance of a smooth toroid and one made out of 7 rings is almost identical.

    As long as you put in good, verified numbers in JAVATC, the results you get there are very close to reality.

    On a note of pulling wire through holes, that is how I made the Kaizer DRSSTC 1, pulling 8 rings of a helical coil of 10 mm copper tubing through 4 holders. That was a pain, took a lot of oil, hitting, hours and twisting to get it in position, I will never repeat that or advise anyone on trying that. Waste of time.

    Kind regards
    Mads

  39. Exactly. I want the coil to look good.. Cosmetics 🙂
    Pulling wire through holes.. Oil and hitting? Thank you for your advice.. 🙂
    Thank you mads 🙂

  40. hi i’m arvin please help me how to calculating c3 10uf 400v and why you use it tanks
    Merry christmas

  41. Hello Arvin

    C3 is a snubber capacitor to protect the IGBT switches. If you want to calculate its value, search on the internet for IGBT snubber design. As a general rule you can also just use somewhere between 1 to 10 uF, voltage rating higher than your supply voltage to the bridge. The capacitor have to be a snubber capacitor or other pulse rated metallized film capacitors.

    Kind regards
    Mads

  42. Hello Mads Tanks for helping me.and can i use TVS 1.5KE440CA for IXGK60N60CD1 or 1.5KE350CA for IRFP460&IRFPS37N50A

  43. Hey Arvin

    Choose the TVS so that enough in series protects the switch from voltage spikes of a higher voltage than their rating. F.ex. use two 440 volt TVS for protecting a 600 volt IGBT.

    Kind regards
    Mads

  44. Hi Mads

    Two 440V TVS in series, wouldn’t kill spikes the IGBT(600V) before it clamp by the TVS (880V) ?

  45. Hey Arvin

    The TVS, together with the snubber capacitor C3, forms a protective network for the IGBTs. Short spikes does not have the energy to destroy the IGBT so hard clamping is not needed before it is getting real serious. C3 will also take care of some of the spikes.

    Kind regards
    Mads

  46. Hi Mads
    i hope you can help me again.After a while i decided te test my UD 1.3 driver like you did, i used signal generator to test OCD and it is working but one thing is not going i can’t get interrupter led flashing. Interrupter i used is one from oneTesla midi/fixed and hfbr1412. the diode in hfbr1412 is on but you can barely see it and when i connect fiber to it on other end of fiber i cant see nothing so i used my phone camera and there is some light but i am not shure if it is enough.On the hfbr2412 output there is nothing.
    thanks
    Dario

  47. Hello Dario.

    Steve used a opto receiver that inverted the signal. So be sure that you are sending the same kind of signal as you expect to receive at the driver. Maybe the battery for the interrupter is too low?
    Kind regards
    Mads

  48. Is it possible that problem is that Ward use OPF2412T OR HFBR2412T and i have HFBR2412TZ??
    Thanks

  49. Hey Dario

    The three receivers your listed are the exact same circuit, if you look at the datasheet, the Z indicates that the part is RoHS compliant, so nothing to do with operation.

    Remember that the interrupter sends a, perhaps, 120Hz signal at 200uS, this is a very short pulse and will look very faint when you look at the fiber cable, so it sounds like it is fine.
    The problem must be at your receiver.
    I removed that interrupter LED from the UD1.3, it gave me some problems, maybe you are having the same problems?

    Kind regards
    Mads

  50. Hi Mads
    since i must wait for parts to repair fiber optic i dicided to go on with my 60n60 halfbridge.
    90% is done (gdt,tvs,screw terminals…) i made pcb in eagle similar to easternvoltage one.
    I noticed that you and others are using this two capacitors (voltage devider) for bridge.
    Why is this sistem better than connecting it direct no negativ rail without 2 cap.??
    Do you suggest i do the same or should i go direct to negative.??
    I wont be using doubler since i have main 220ac.

    Thanks
    Dario

  51. Hey Dario

    When switching a inductive load with a half bridge, there will be some heavy back emf from the load. The capacitors help filter these low order harmonics out from interfering the DC bus voltage, the voltage could have sudden transients that in worst case would destroy the switching devices.
    The supply voltage is however half of the input voltage, which is why you often see better performance when using full bridges that switch the full voltage.
    You can try to tie the load directly to the negative rail and do all you can to protect the transistors from transients.

    I look forward to hear about your progress and experiences.

    Kind regards
    Mads

  52. Thanks for explanation
    but then is very important that this two cap’s are not only mpk they must also be same quality as mmc because of peak current??
    The qualitty of them can also improve the output of Coil?
    In your project you use 1uf MPK but i also saw people use the well known CornelDoubillier 0.15uf/0.33uf 2000VDC,the same like MMC.
    Dario

  53. Hey Dario

    The voltage divider capacitors only sees the current being drawn from the DC supply, not the peak currents that float in the primary circuit between primary coil and tank capacitor. So you can use either one.

    As long as you use polypropylene capacitors with a low ESR it would properly be that best bet, a high dv/dt rating will also indicate that they can deliver energy fast.

    Kind regards
    Mads

  54. Hi Mads,

    I’m wondering how you determine the phase of the current transformers and how you change the phase. Do you just reverse the leads from the current transformers ?

  55. Hey Ray

    You just have to try it one way or the other. You can either turn the transformer 180 degrees or reverse the leads going to the driver board.

    Kind regards
    Mads

  56. Hi Mads,

    Thanks for the quick reply. Does the phase of the OCD current transformer matter ? Or can it be used both ways and only the phase of the feedback transformer matters.

    Thanks,
    Ray

  57. Hello Ray

    As the input from the OCD CT is rectified to a DC positive level voltage, it does not matter what phasing it has.

    The OCD circuit will only disable from the next cycle and not the current one triggering the OCD, so even if it is phase shifted it will still be tripped for the next cycle.

    Kind regards
    Mads

  58. Hey Paul

    I use cascaded current transformers for both feedback and OCD, they are both the same, it consists of two cores with 33 windings on each and one winding going through the second to get a ratio of 33:33:1.

    It is the same as a 1:1089 ratio current transformer, just so much easier to wind by hand.

    Kind regards
    Mads

  59. hi
    I am making your model Tesla coil, but I have several factors which give me a spark of about 2-3 cm away; I’d like to orientaras in siguuientes questions:
     
    the secondary coil is of 26 gauge copper wire: .4mm in diameter, which is coiled to a PVC tube 4 inches and height of the tube is 1.10 meters, so that 1750 turns have.

    in the primary coil is not that caliber copper put, also the number of turns I have to do for this; distania between each of the laps.

    handling a voltage of 110 volts, that factor I think is important but I’m not so confident to increase to 220 by So please help.

    that often I can and I have to make it work?

    to make the small winding (the terminal named A -A, -B B, C -C, and -D D terminal is directed to the primary coil) so do 15 laps, this is correct or advice me das?

     that way I can increase the beam pulling the coil?

  60. Heloo Mads

    I build a full bridge with irg4pc50ud. They are rated for 600V. I power my brisge wit wariac0-240v. The max input that I can put into bridge is 120VAC this is 170VDC on bridge. I set ocd to 200A.
    I want to know how I can put 230VAC into bridge. I was testing with lower BPs and time but without luck.
    Must put higher OCD to 250A?
    Thanks for help
    Matej

  61. Hi Matej

    What is keeping you from using a higher input voltage? Is it the OCD that keeps tripping? It could be bad tuning the makes the peak current fly up high too fast as the energy transfer to the secondary coil is too small.

    Kind regards
    Mads

  62. Heloo Mads
    Yes when I want tu put higher then 120Vac then OCD keeps tripping. JavaTC give me 5 turns of primary for my setup but I must try to find better tuning.
    I was looking smalest peak current on scope when I tune primary. This is OK?
    My secondary has 1200 turns of 0.25mm wire on 110mm tube, topload is 60mm diam and 240 mm mayor diam.Cap I am using is 60nF. The max spark was 35cm.
    Thanks
    Matej

  63. Hi Matej

    35 cm sparks from a coil that size and OCD around 300A is a very good result!

    The longer spark will load the secondary even more and pull down the resonant frequency, so as it makes longer sparks it pulls itself out of tune. So detuning the primary lower than secondary only works to a certain degree until it is too much out of balance.

    I hope you will come to http://www.highvoltageforum.net and show some more details about your coil and how you built it 🙂

    Kind regards
    Mads

  64. Heloo
    I was mesuring the current with 1:33:33 current transformer with 10 ohm burden but I have a lot of spikes when mesuring. Must I take a biger value of burden resistor for a better waveforms ?
    If I put higher voltage the spikes are even biger.
    Thanks
    M.

  65. Hello, sir.

    I have been doing research into building an SSTC, and this seems to be the best one I have found so far, with cost in mind (I am a high school student). Would you be able to send me schematics, etc.? I have found very little information with regard to schematics. Thank you very much. Best regards, James.

  66. Sou Brasileiro sou fascinado por bobina de tesla, mas não sei como fazer!
    Você poderia me ajudar ?

  67. Hi Marcel

    I bought them new from digikey, not cheap, but seemed to be the only place to get them at the time when I built this coil.

    Kind regards
    Mads

  68. Hello,

    I am planning to build my first DRSSTC. I read your designe guide and tried to use the formulars on this “example” coil to check if I am doing things right.
    Unfortunately i got some different results and I dont know why.
    For example: if i use the formula for the maximum On-time from the MMC design guide on this coil with a peak Voltage of 3200V (for the 4000VDC Cap) and 210*sqrt(2) supply Voltage, my result is about 11 half-cycles. In reality you are using 35 primary cycles which is obviously a lot more. Is this the result of de-tuning the primary? so current and voltage rising slower?

    And is their an easy way to calculate the AC input current?

    I would be very happy if someone could help me with this.

    Kind regards
    Kai

  69. Hi Kai

    The short answer: Here you find the LC circuit theoretical limit, what you set your OCD to will limit this and you can push it for longer as it cuts out once in a while. This calculation also does not take into account that you transfer this energy from the primary circuit to the secondary circuit and out into the load that a spark is. So once the energy is transferred through the system, it should not continuesly be rising, but be “stable” and feed into the spark. This is why you see me running 35 primary cycles.

    About AC current, I think it is easiest to look at the DC bus capacitor calculations.

    Sign up at http://www.highvoltageforum.net and tell about your project and you will have many more people helping you 🙂

    Kind regards
    Mads

  70. Hi all,

    I would like to equip my OneTesla TS with an OCD. However, I have noticed that the power sensing is made by two toroids glued to eachother while only one of them hangs in the primary loop. Can someone explain to me thy there are two toroids and how they are wound and connected to eachother? Would it not work with a single toroid?

    Thanks for your help.

  71. Hi David

    Cascaded current transformers are used from a practical view point. The first toroid has 33 windings and 1 turn of this goes through the second toroid, which also has 33 windings. This gives a 33×33 = 1089 current ratio from the primary cable passing through the first toroid. If you were to use a single toroid, you had to wind 1000 turns on it, usually by hand and that is tiresome and not very practical.

    A single current transformer will work fine, some even uses 100 turns and a different shunt resistor value to match it, but you have to watch for phase shift and such when you do that.

    Kind regards
    Mads

  72. Hi Mads!
    Your work is amazing, always interesting to read. I studied your guides and other tesla coils you have made and I have decided to build small and reliable DRSSTC like your DRSSTC II, so I can experiment a bit and learn something new during the process, you know, things you cannot try with huge and powerful coil. I am making it the same way as you, my secondary is done and now when I moved to primary, I got confused. Is the inner diameter really 70 mm? It should be, because the calculations are correct with that value. But, just when I looked at the pictures you posted, I measure just a bit more (like +10 mm in average). (Looking at your flat primary calculator, there is a explaining picture showing where the inner dia is located.) Where is the problem?
    Thanks

  73. Hi Jetam Sekuh

    Thank you very much for your kind words.

    Pictures can be deceiving, you will see that if you choose to upload some pictures of your own project, so something like http://www.highvoltageforum.net

    Everything looks better in pictures, but the perspective can get a little skewed.

    I took out a ruler and measured, just to be sure. The primary coil is actually a tiny bit oval so the inner diameter of the primary coil is 70 mm on the shortest and 76 mm on the furtherst.

    Do not worry too much about many of these small details and assumptions, building a Tesla coil with all the rules of thumb we use, it is all still within +/- 3 dB 🙂

    Kind regards
    Mads

  74. Thanks a lot. I totally forgot that such a small detail is really not going to make my coil explode, I can probably tune everything correctly when the coil is done.

  75. I got some wierd stuff going on.
    I built the UD 1.3b on some prototype board. When I wanted to test the GDT i wound, I simply plugged 300khz square wave (50% duty cycle) from 555 timer circuit into the GDT driving stage. I did not have 2 channel MOSFET driver laying around, so I just used 2 UCC37321 and IRF5210 with IRFZ44 MOSFETS according to the schematic. What was noticable right after powering up the circuit was the rather high current draw, which heated up the P channel MOSFETS and the UCCs. I am lucky I used current limited supply.
    It kind of surprised me, because the N channel Mosfets were getting much less hot than the P channel ones. I checked the output waveform with oscilloscope, and it was just fine (I had to lower the frequency, so that the UCCs and Mosfets do not blow up before I connect the oscilloscope). Any help with this part of the UD 1.3B?

    I already wanted to sckratch the idea of using Mosfets. I would just hook up the GDT directly to UCCs, but I am using minibricks and I am worried the UCCs would not be powerful enough to drive the bricks properly (since UCCs can only handle 15V). But I am not sure, because this is my first proper DRSSTC.

    I am not gonna push some high currents through the primary. I think +/- 300A MAX, even thow I could use higher currents since the IXA70I1200 minibricks I am using are more powerful than 60N60. But I am aiming for 20cm sparks MAX. I am here to build small DRSSTC and gain some experience, so that I can make big DRSSTC later on.
    Thanks

  76. Hi Jetam Sekuh

    Maybe cross conduction from the 50% duty cycle, since you skipped the delays voltage drops of the FB circuit, there could be an issue from just injecting the signal in the middle of the circuit. What I have done was to inject the signal generator at the FB CT input to get the correct simulation and OCD CT can just be a DC voltage to simulate the current level for adjusting OCD.

    It is best to use the MOSFET output stage, you need a stiff gate drive at 24VDC when we drive these IGBTs in resonant mode over their current specifications. The normal +/- 15V will result in too slow turn-on and higher switching losses, ultimately failing IGBTs from too high die temperature.

    300A seems like an absolute minimum in a DRSSTC, when looking at the on-times typically used. Lets say you could get longer streamers at 400A, with a shorter on-time than at 300A, then your switching losses would likely be lower at 400A than 300A. It can be hard to grow sparks at 300A without a long on-time, so not to ruin your plan, but do not hesitate from trying a little higher 🙂

    I trust miniBlock IGBTs to 500A, not more, I blew a set of 60N60 up at 700A 🙂

    Please do come to http://www.highvoltageforum.net and make a thread about your project, for additional help from other users!

    Kind regards
    Mads

  77. Thanks for reply.

    I tried what you advised. Connected function generator (set to 300kHz. 50% duty cycle) instead of the FB CT. I also hooked up the OCD circuit and prepared everything.
    I scoped the signals in different spots of the circuit. Everything is OK and I got beautiful square wave at the output of the AND logic gate. The OCD works just fine as well. The only thing not working properly is the MOSFET output stage.
    I still got the overheating problem. MOSFET drivers output correct signal and feed it to gate of N channel MOSFETs and to the P channel ones through the capacitor. But the MOSFETs take around 200mA from the 24V supply, that heats them up. And when I connect GDT to the output, the current rises to 1A destroying the P channel MOSFETs.

    I think there is problem with the IRF5210 P channel MOSFET I am using. Probably think I should buy the FDD8424 dual MOSFET that was used in UD 2.7. But I am not sure, I have not seen anything like this before and I have got no idea what is going on with my output stage.

  78. Hi Jetam Sekuh

    I used through-hole parts IRF540 and IRF9540 for the output stage, with small heat sinks they can take a lot more abuse.

    Kind regards
    Mads

  79. Hi Mads

    Thanks a lot for everything you have shared here, it’s a great reference!

    How accurate have you found JAVATC and your primary calculations spreadsheet to be? I ran your secondary design through JAVATC and it was quite different to what you found in practice. It reported a secondary resonant frequency of 174 KHz which is far from 372 KHz.

    Thanks, Shaun

  80. Hi Shaun

    It seems you were fooled by the secondary dimensions input fields, which request a RADIUS and not the DIAMETER. I have made this mistake a few times myself 🙂

    Kind regards
    Mads

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