High Voltage Forum
Tesla coils => Dual Resonant Solid State Tesla coils (DRSSTC) => Topic started by: Skylex86 on October 11, 2018, 09:11:50 PM
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Hello
I just started making my first DRSSTC
It is based on the onetesla CARD, with some improvement : - 1200µF capacitor
- rectifier weight of 50A in 1000v
- 2*2 IGBTs in parallel (FGA60N65SMD)
I have already done the secondary winding, the torus, the power supply system with filter, circuit breaker and high power relay to disconnect the power supply
the thing is that I don't have much room for error because my budget is very tight.
and I would have liked to know if there were any improvements to be made to this control card ?
here are some pictures :
(https://zupimages.net/up/18/41/dm2g.jpg)
(https://zupimages.net/up/18/41/rjzm.jpg)
kind regards
alexis
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Hi Alexis and welcome to HVF :)
It looks like you have a plan, but please do tell more details about your resonant frequency, MMC size etc.
As this is your first Tesla coil, it is better to keep it simple and get it working before you think about improvements.
Your topload, secondary coil and primary coil looks fine, no critical errors but a few things to think about:
1: wooden primary coil supports can be prone to failure if the wood becomes conductive due to moist
2: the high voltage sticker on the secondary coil could also lead to flash overs simply from being another material, the adhesive changing the varnish underneath or just by supplying a edge along which the arc can track. High frequency high voltage works in mysterious way.
Looking forward to see your build progress and eventually some sparks :)
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Thank you Mads Barnkob for your answer
it's true that I didn't go into too much detail
the primary coil measures 10µH
And the resonance frequency of the secondary is 130KHz
which must give me a 149nF MMC capacitor
what tolerance can be given to the capacitance of the MMC capacitor ?
my secondary winding makes about 2200 turns (cable 0.25 mm by 550 mm)
It is covered with 6 layers of polyester resin
the sticker is just a piece of paper, placed between the 5th and 6th layer of resin
how to know if wood is "conductive" ?
and what damage can it cause ?
kind regards
alexis
P.S : today I made the SD card reader
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Wood can become conductive when near high frequency high voltage because at high frequencies the insulating material properties changes from regular DC current behaviour. If it is moist, which most wood is to some level, it can conduct current. If there first is a single strike and a carbon track is formed in the wood, it will flash over the second after and start burning as long as you are pushing current into it. So avoid using wood in direct contact with high frequency high voltage.
The current through the primary coil is determined by many factors and no matter what design you have made, you can always limit it by lowering on-time to reduce number of cycles on which the voltage can build up or use a OCD setting that protects your IGBT within some limits you define after calculating the maximum current you will allow through it (example calculations here: http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/igbts/ )
I have not yet finished my MMC guide, where I explain all the math regarding calculating the primary current determined on peak voltage from the on-time/cycle settings. Because you also need to worry about the peak voltage across your MMC and not just the peak current through your IGBT, its all interrelated. The below text is from that yet unpublished article:
To use the same example I will once again use the 0.45 uF MMC where I choose to use six parallel strings of two CDE 942C20P15K-F capacitors in series. Each capacitor has a DC voltage rating of 2000 V in a 4000 V series rating, but for protection I will derate that 20% so the calculations are done with a maximum allowed 3200 V across the MMC.
Peak voltage V_peak is given in Volt, Primary inductance L_primary is given in Henry and frequency F_resonant is given in Hertz.
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The result shows with good precision why I ran my DRSSTC1 at 500 Ampere OCD settings, as this corresponds to the low voltage rating of the MMC, but not lower than it was a good match with the IGBTs used.
The maximum on-time to stay below 3200 V across the MMC, and thus also stay below 472 A peak primary current can be calculated, but it is dependent of the inverter type.
The maximum on-time for a full-bridge
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5 half-cycles at 70 kHz on a full-bridge, according to table 2 is around 35 uS before we have either 3200 V across the MMC or 472 A flowing in the primary circuit.
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hello
what should be the minimum and maximum value of dV/dt?
because I would like to use these capacitors
https://www.digikey.fr/product-detail/fr/R474N315050A1K/399-12724-ND/5731215/?itemSeq=274045822
I will connect them six in parallel and six in series
which would make me 0.15µF for 6000V
according to this formula :
(https://highvoltageforum.net/index.php?action=dlattach;topic=484.0;attach=2445)
I find 550 A peak
What do you think?
in another subject I read that you should not use simple DRSSTC circuits
but these use expensive fiber optic respirator emitters that are expensive
except this one (and others) :
http://kaizerpowerelectronics.dk/wp-content/gallery/2011_08_14_-_kaizer_drsstc_ii/IMG_5158.jpg
but every time there's no schematics.
so there are two possibilities for me :
or I find the schematic of one of these control charts
or I adapt an OCD system on the onetesla card
as here : https://www.google.fr/search?q=ocd+onetesla&safe=active&client=opera&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiss_2K8oveAhUFxxoKHWOhAwEQ_AUIECgD&biw=1280&bih=883
what do you think is best ?
kind regards
alexis
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hello
what should be the minimum and maximum value of dV/dt?
because I would like to use these capacitors
https://www.digikey.fr/product-detail/fr/R474N315050A1K/399-12724-ND/5731215/?itemSeq=274045822
I will connect them six in parallel and six in series
which would make me 0.15µF for 6000V
according to this formula :
(https://highvoltageforum.net/index.php?action=dlattach;topic=484.0;attach=2445)
I find 550 A peak
What do you think?
As long as you use MKP/PP type capacitors, dV/dt will never be an issue, since these capacitors ratings for pulse currents is already in the range of what we need.
You found a X1 safety capacitor used for EMI input filters, while this is a regular MKP capacitor, their datasheet does not specify its current capabilities and their dissipation factor also does reveal that it might not be useful in pulse application, 0.1% at 1 kHz is already very high and now at 100 kHz that will get even worse, my best guess is you would set there capacitors on fire if you run that coil for too long. Find a capacitor that has a datasheet with RMS and peak current specifications and how to derate that to frequency etc.
550Apeak is properly right if you put in 6000Vpeak, so this would be your maximum OCD setting in order to protect your MMC from overvoltage, but you still need to find out if your IGBTs can handle 550A, which I do not doubt, but you can always do the math to be sure :)
in another subject I read that you should not use simple DRSSTC circuits
but these use expensive fiber optic respirator emitters that are expensive
except this one (and others) :
http://kaizerpowerelectronics.dk/wp-content/gallery/2011_08_14_-_kaizer_drsstc_ii/IMG_5158.jpg
but every time there's no schematics.
so there are two possibilities for me :
or I find the schematic of one of these control charts
or I adapt an OCD system on the onetesla card
as here : https://www.google.fr/search?q=ocd+onetesla&safe=active&client=opera&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiss_2K8oveAhUFxxoKHWOhAwEQ_AUIECgD&biw=1280&bih=883
what do you think is best ?
kind regards
alexis
Fiber optics is not cheap, not even the cheapest, but it is the best choice for human safety and operational stability.
All my coils on kaizerpowerelectronics.dk uses Steve Ward's drivers like the UD1.3, which is the one you linked a picutre to, https://www.stevehv.4hv.org/new_driver.html or the newer driver with phase compensation circuit, https://www.stevehv.4hv.org/leadcomp/
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I agree that fibre optics is the best solution in terms of security
but on the picture above the receiver used is comparable to the one used
https://www.digikey.fr/product-detail/fr/IF-D95T/FB123-ND/243780/?itemSeq=269844015
and it costs less than OPF 2412 (and other)
so if I replace an OPF 2412 with an IF-D95 will it work ?
Alexis
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They are both give CMOS/TTL compatible outputs, but the OPF 2412 has a NOT gate on the output, so polarity of the two receivers is opposite, so you need to add in or remove a hex-schmitt trigger gate on the driver board, there should be one available when its the regular Ward UD1.3/2.1.
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Mads Barnkob
thank you for your answer
would you still have at your disposal the diagrams and files used to make your DRSSTC 1 OR 2 ?
it would save me the trouble of having to do them again.
another question, I've been running your youtube channel for a while now and I saw that in one of the video vaux you were "dismantling" a server inverter
where did you find it ?
thank you in advance
alexis
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hi
today I'm almost done making my control box
(https://zupimages.net/up/18/43/7gr6.jpg)
(https://zupimages.net/up/18/43/mvlo.jpg)
it includes the entire power management system of the DRSSTC (a large relay controlled by several switches, the 230v filter and an emergency stop)
it also includes the interrupter (which is not yet finished for him)
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hello
I have just finished modifying the schema to use a TTL fiber optic transceiver
He's on my drive
(https://zupimages.net/up/18/43/d2dh.png)
https://drive.google.com/open?id=1IeWnqPCSSu1kxaGyyZuOufIun5g1LoJA
Could someone please check that I didn't make a mistake ?
(except MOSFETs and resistor and condenser values)
thank you in advance
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I never shared the board files as I never got them up to a public state in being error free and its not really a priority for me to get that work done. You can find eagle boards files on Wards home page for his drivers.
I find all the equipment in my videos on privately owned metal scrap dealers grounds.
Comparing your schematic to Wards UD1.3b ( http://www.stevehv.4hv.org/newdriver08/DRSSTC_pndriver1_3b.pdf ) you seem to have left out C3 and you did not connect pin 2 and 4 on your IC5A to +5V.
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Thank you Mads Barnkob
indeed it was missing C3 and the +5v on IC5A
I based myself on your UD1.3b
I just added a hex-schmitt trigger gate at the output of the fiber optic receiver
another modification I will make is to separate the different parts of the circuit on several PCBs
it will be easier to do (of course all PCBs will be in the same metal box)
alexis
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Hello
I finished making 2 PCBs ;
(https://zupimages.net/up/18/44/ambr.jpg)
(https://zupimages.net/up/18/44/b0jv.jpg)
I still have one more to do.
celui avec le LM311, le détecteur d'intensité et celui pour désaccordé avec la fréquence de résonance.
Alexis
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Nice boards, I assume they are all homemade.
How did you do the silkscreen? And a little funny with a mirrored silkscreen sitting on the opposite side of a surface mount component board :)
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Nice boards, I assume they are all homemade.
How did you do the silkscreen? And a little funny with a mirrored silkscreen sitting on the opposite side of a surface mount component board :)
I'm guessing that silkscreen is toner transfer? If so, nice trick, never tried it when doing my own PCBs.
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Nice boards, I assume they are all homemade.
How did you do the silkscreen? And a little funny with a mirrored silkscreen sitting on the opposite side of a surface mount component board :)
I'm guessing that silkscreen is toner transfer? If so, nice trick, never tried it when doing my own PCBs.
That's exactly what it is.
I thought to myself if it works on copper it must work on bakelite
so I tried it and here's the result ;D
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Hi
After a short pose in the realization of my drsstc, I restart
I first redid the primary coil support, then I added a second torus to drop the resonance frequency and to finish, I finished the security part of my control desk.
(https://zupimages.net/up/18/50/bt61.jpg)
I still have to order the components to make the electronic cards
but first I have a few questions :
- for ferrite rings are there any characteristics respected ?
- how do I know if my IGBTs will withstand 550 A peak ?
because on this DRSSTC, I peak max is 500 A, but these IGBTs only resist 300A max !
- what do you think of these capacitors (https://www.mouser.fr/ProductDetail/KEMET/R474N31005001K?qs=sGAEpiMZZMu3dWSqd4Tl0Fd7dHVopjbiki9cBgNAjKv9dySeLvLI4A%3d%3d) ?
because Mouser no longer has a Kemet R474N247000A1K in stock
thank you in advance
Alexis
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Here is a good guide on finding the right material and making your GDT: http://thedatastream.4hv.org/gdt_index.htm
You can either calculate what kind of load your IGBTs can withstand or you can base it on others experience with pushing that part to a certain peak current: http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/igbts/
I would not use those X2 Kemet capacitors for a MMC, they are not made for the job. They have a low dV/dt rating and its hard to get any other specifications on it. You can properly compare it to the Kemet capacitor I added in this list: http://kaizerpowerelectronics.dk/theory/good-mmc-capacitors/ and you can try to give it a design go at: http://kaizerpowerelectronics.dk/calculators/mmc-calculator/ but be aware that there is currently a error in the MMC calculator regarding temperature rise, so it might be 10-20 times too small, I am looking into that issue.
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Hi
Since I'm not the budget for big IGBTs, I have chosen to use FGA60N65SMD.
According to Mads Barnkob's painting, those if can hold 300 A Peak (http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/igbts/).
So I'm going to put three in parallel which should make me 900 A peak
Here is the circuit :
(https://zupimages.net/up/18/52/i7zb.png)
What do you think?
Sincerely
Alexis
Merry Christmas and a Happy New Year !
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Hello everyone
I'm back after a few months of absence
I have made some progress on my DRSSTC project, I received all the components for the management cards.
I finished putting them together this weekend.
(https://zupimages.net/up/19/19/0j3f.jpg)
I also found a large capacitor
(https://zupimages.net/up/19/19/n4np.jpg)
the support of the primary coil has been painted
I got a metal box to store the control cards, in addition to the fence that will be put all around it
I still have some measurements to make, in particular the inductance of the primary coil to be able to calculate the value of the resonant tank capacitor and also soldered the interrupter (It's the same as the one onetesla TS).
a quick question:
can we test the control board without the high power part ?
Alexis
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Good to see your progressing well with your coil and I love your home-etched boards, looks just like mine :)
A word of advise on the zipties on the primary, if your primary coil heats up zipties are very easily loosing up and the little tap will let go, perhaps shorting out a few turns of your primary coil. So be sure to watch the temperature of it or you could fasten the turns with stiff copper wire, you have enough space to avoid short circuits from that.
You do not really need to do measurements of your primary inductance, JavaTC is so close to reality that you can just plot your dimensions into that: http://www.classictesla.com/java/javatc/javatc.html
You can test the UD without power on the bridge, but you need to "fake" the feedback. Use a signal generator to feed a sine wave into the rectifier diodes of the feedback input. You can use a power supply for the OCD voltage level, just inject it after the diodes, or use a 2nd signal generator if you have one.
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Hello
Well, it's not moving very fast for the moment but it's going to change !
I'm finally on holidays !
I receive my function generator next Monday or Tuesday.
today I made the rolling base of the tesla :
(https://zupimages.net/up/19/26/kwwo.jpg)
tomorrow she's going to paint.
I have one more question about IGBTs
I found a 5SNS 0300U120100, not very expensive and not far from home
what do you think of this IGBT module ?
Here are the Datasheets :
https://datasheetspdf.com//pdf-down/5/S/N/5SNS0300U120100-ABB.pdf
Thank you in advance for your answers.
Alexis
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Do not worry about time flying, some of my coils took years to finish :)
Those ABB 3-phase IGBT bricks would have to be used as half-bridge bricks where you drive en 3 half-bridges in parallel and combine the output terminals, both for making a half-brigde and two of them for a full-bridge. Their switching speed is fair for maximum 150kHz (I did not check heat dissipation! Just looked at the times), it has a good high pulse current rating and short-circuit rating, but BUT, there is always a but. The gate charge is really large and it will require much more from your driver, so you have to check your 24VDC rail on the driver and see if its sagging, you might have to add a more powerful external gate drive voltage power supply instead of a 24V 1A regulator. http://kaizerpowerelectronics.dk/calculators/igbt-gate-drive-calculator/
Your control box is looking good, what kind of safety features did you put in it? I see emergency stop and what does the switches and lamps do?
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Hello Mads
If the only problem is that they consume a little more than the others, I make them eat differently
unless the rev 1.3 card is not able to support the required intensity
What do you mean by:I did not check heat dissipation ?
according to the datasheets I would have 960w to dissipate
Total power dissipation Ptot Th = 25 °C, per switch (IGBT) 960 W
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With 6 gates in parallel, for a full-bridge, you would need atleast 10Apeak driving power and 0,144A average driving power, you risk having sagging 24V from that heavy load, so beef the 24V rail up with larger lytics, but I also think you need something larger than a 24V 1A linear regulator.
All datasheet parameters are given for hardswitching in a regular inverter type of application, like a motor drive.
A DRSSTC utilizes softswitching/resonant switching to handle the much higher peak currents we need for spark generation in a very short time.
You need to calculate the Fmax2 value and you can follow my guide here on how to do it: http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/igbts/
Just remember there is a lot of assumptions and it is worst case scenarios, so you can tweak some of the values of derate them even further, it all just comes at the cost of lessened life time of your components :)
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Your control box is looking good, what kind of safety features did you put in it? I see emergency stop and what does the switches and lamps do?
The lamps are used to know which safety is activated (When there is just the power supply connected the green light is on, if the circuit-breaker is passing through then the orange light comes on and if the electromechanical contactor is also passing through the red light comes on).
Moreover it is impossible to turn it on without a key
The rest is used by interrupter (the screen and the red buttons).
I'm programming the atmega of the interrupter
I calculated gate charge :
(https://zupimages.net/up/19/27/ay3q.png)
but I couldn't find gate resistor int
I also tried to calculate Fmax2,but I couldn't find RθJC, Pcond
But i compared the CM600DU-24NF with the 5SNS
I compared the CM600DU-24NF with the 5SNS
The 5SNS takes less time to activate and deactivate, Total power dissipation is much higher for the CM600
I also measured the inductance of my primary coil, I am at 7µH. Then I calculated it with JAVATC and it shows me 7.28µH
So I will start on 7µH and take access to the capacitor to be able to tune it between 6.5 and 7.5µ
otherwise the trolley has been painted, it already looks better :D
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Hello everyone
It's been a while since I've been here. The tesla coil hasn't progressed much since the last time.
I had other important projects to take care of and with the studies, I had even less time to devote to them.
But having a little more time at the moment, I decide to get back to it.
I recently received 5 igbt SKM 400GB 17E4.
I think they will be able to go well beyond the 500A spike I was considering.
I'm going to resume the calculations to finish the power part of the tesla.
I will keep you informed of my progress.
Have a nice day
Alexis