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Messages - Mads Barnkob

Pages: [1] 2 3 ... 46
1
Solid state Tesla coils / Re: New small SSTC
« on: April 18, 2019, 10:28:28 PM »
SSTCs likes big topload, it generally gives larger sparks. But there is a tipping point where it becomes too large a load for the inverter, not something I know more about in detail than that.

I would say that adding a topload that has a major diameter even to your windings length of the secondary and a minor diameter even to the secondary coil diameter will give you a good all-round solution.

2
Dual Resonant Solid State Tesla coils / Re: Secondary Design Tool
« on: April 18, 2019, 10:24:33 PM »
Great job on doing more calculations on the magic 50k impedance, however you do get very narrow around it and remember, it is just a guide line, many other configurations work.

In your GUI the slider only have a narrow defined range and no scale, it only goes up to 110mm.
It is not possible to make calculations on coils outside of 45-55k, which is a shame, it is also good to see the the outer limit results.


You made a nice little tool, especially with the JavaTC export.

3
Great video and excel sheet Pete, thank you for sharing. I also have some fiberglass hose in the mail, however long its going to take from China, but then I will box up the heater with the 3 server power supplies.

4
Dual Resonant Solid State Tesla coils / Re: My first DRSSTC on bricks
« on: April 18, 2019, 09:51:49 PM »
Great progress and big thumbs up to Netzpfuscher for the support!

You driver is just sitting in a plastic enclosure, I always use a metal box which gets grounded, switching noise is pretty massive so close to the primary coil. My large DRSSTC can knock out my camera at 50 cm distance when running with a static load.

Looking forward to see your first sparks on the UD3 and also a big thank you for sharing your fault tracings on the UD3, this will all help future builders!

5
Beginners / Teach your kids electronics
« on: April 17, 2019, 11:51:59 AM »
I could write a long motivational letter about the importance of teaching on electronics with all its basic trades of logical thinking and scientific methods, but instead I will leave you with the happy face of a 5 year old that completes her first little project :)


6
Dual Resonant Solid State Tesla coils / Re: Drsstc 3
« on: April 10, 2019, 12:21:20 PM »
Cheers for the guidance Mads. Is having a upsidedown U primary the same calculation as a flat pancake?  I had a quick look at your drsstc that uses one, looks extremely nice.

I think I just went with a median value based on spiral coil and coupling as if it was a helical, but as you can see from the article on my website, I did a lot of measurements instead, as I could not calculate its specifications.

I guess you have to use something like FEMM in order to get a correct simulation as spiral/helical calculators and javatc does not support that primary form.

7
Dual Resonant Solid State Tesla coils / Re: Drsstc 3
« on: April 10, 2019, 09:13:24 AM »
For about a month now I've been put off on this project, I really couldn't be bothered making any progress and I couldn't figure out why..... Then it hit me! I hate the look of it 😢

Basically I had a 450x450x350mm "cube" for the base of the coil, to me that's pretty unappealing. One look I do like are round bases both a helical primary. Apart from Mads drsstc 1 I haven't really seen bigger drsstc with helical primaries at all, unless having a pancake primary was more of the norm 5-10 years ago?

So my question is, are there any drawbacks from having a helical primary at this size I can't think of?

Good old Dr. Spark, which seems to have closed down his website, primarily built helical primary coils and they performed great!

Now I built a helical coil on my first DRSSTC for several reasons:
- To make the coil take up less space, smaller diameter
- I thought it was easier to make primary coil holders for this type compared to spiral
- Tapping was easier with cable just going up the side

I will avoid helical coils in the future for the following reasons:
- It has a high coupling that is harder to adjust/control
- It is much closer to the topload, so there is more strikes to ground rail
- It was a pain to wind the coil through the 4 sheets with too small holes, it took me hours to move it centimeters at a time as it kept locking itself in place
- There is no performance gain over spiral, for a DRSSTC

I would however still make round platforms with spiral primary coils, as I think they look great, but when you get up in size you really need a bigger base to stabilize the thing with wheels out in the corners of a box.

You could also go inbetween spiral and helical and make a upsidedown U shape primary if you want it to have a smaller diameter overall.

Looking forward to see what you decide on :)

8
Beginners / Re: Why ZVS always use regulated PSUs?
« on: April 10, 2019, 09:03:10 AM »
I have used it all.

Iron transformers of all kinds, rewinded microwave oven transformers, scavenged 24VDC AC transformers from industrial power supplies, halogen lamp power supplies and old welders, they are almost impossible to kill but they have a slight disadvantage when it comes to overload. A overloaded / saturated iron core will drop in voltage up until then point of saturation, which often can lead to MOSFETs dying from poor switching if the voltage drops below 10VDC.

SMPS are however becoming very easy to find surplus from old servers and when they are overloaded they make a over-current shutdown instead, which in my experience does not result in near as many MOSFET deaths as a underrated iron core can if a certain high load is suddenly presented to it.

Iron core only fill up its capacitors at 100 Hz vs. SMPS that maybe run at 100 kHz and has a extremely fast load condition monitoring to regulate the output voltage, so SMPS is doing better in my book.

9
Spark gap Tesla coils / Re: Resisitors
« on: April 10, 2019, 08:30:58 AM »
You can also find many sellers of resistors on ebay, just have to filter out all the "0.1 to 10M range kits" and you can find something like this: https://www.ebay.co.uk/itm/Resistors-Metal-Film-50-100-pack-1-4w-0-25w-1-many-values-UK-Stock/122130944261?hash=item1c6f925105:m:mfhX03HJfxy0iAdoJS6SO5g

10
Spark gap Tesla coils / Re: Would this be about right or not.
« on: April 10, 2019, 08:27:57 AM »
I am shooting for a coil secondary that will have 24 inchs of 24awg  wire. My wire is .0223in  so to get 24 inches i will need about 1075 turns. My question is some sites say shoot for 800 turns, some say 800 to 1000. Will this be ok at 1075 turn


Thanks to all the reply's. The secondary is 6 to 6 1/2 inches. I read others say only use 22 awg, but I already ordered 24.

Thanks for the charts also

Do not worry about 24 vs. 22 AWG, you have a solid design that pings in at some 42,000 impedance, just shy of the "magic" 50k that will almost always give good performance. So now that you know its on the lower side, you can design your spark gap to be as aggressive as possible to deliver high and fast peak currents, because your coil is not designed for slow pulses (high impedance)

Looking forward to see your results and please add some pictures as you build things :) Seeing a 30 year old dream come true is great!


11
Hi  sjsimmo
Thank you very much about the information “the extra letters at the start and end of part number is importance”.
But, my question still stand there about could HGT1N40N60A4D run up to 1000Apk in a test? As Steve said.
Was that test is soft switching in L1C1 resonance circuit (whithout L2L2 coupling?

Yes, the good old sturdy HGT1N40N60A4D could run at 1000 Apeak, but it ran out of supply and the newer generations were not over-built in the same way, the die got smaller and they were rated for less peak current and less dissipation. Steve was just lucky that he bought the last stock from mouser if I remember right, he bought some 50 pieces or such.

12
Spark gap Tesla coils / Re: Would this be about right or not.
« on: April 08, 2019, 08:41:13 AM »
I am shooting for a coil secondary that will have 24 inchs of 24awg  wire. My wire is .0223in  so to get 24 inches i will need about 1075 turns. My question is some sites say shoot for 800 turns, some say 800 to 1000. Will this be ok at 1075 turns.

This is my first coil. Thanks

Could you please provide some more information?

What is your secondary diameter? What resonant frequency are you aiming for?

Regarding my table of secondary specifications, green is just a safe choice, yellow will work just fine and red is for experiments where you want to explore the outer bounds of "normal" :)

13
Solid state Tesla coils / Re: The Adventures of Skinny Coil
« on: April 08, 2019, 08:35:07 AM »
Sound like you have some strong harmonics since your driver can catch on to 400 kHz for a 200 kHz system, maybe you have to add some kind of low pass filter to your feedback CT, but that should not be necessary.

How about excessive noise making the driver behave odd? Is it inside a grounded metal case?

I do agree that for 260VAC you should see at least 20-25 cm sparks with a SSTC.

You also mention racing sparks, that usually a sign of too high coupling or very bad tuning.

14
Dual Resonant Solid State Tesla coils / Re: DRSSTC feedback issue
« on: April 08, 2019, 08:25:32 AM »
Hi Radek and welcome to HVF!

Quote
(equals to about 45 apk).


This sound like a very low peak current unless its a QCW? I think you have a too weak feedback or wrong phased feedback/output from GDT.

You have to bench test this with a couple of function generators to make both feedback, interrupter and OCD signal, alternatively you can just use a power supply on the OCD input to simulate the threshold level, but then you got no test if it can catch the peaks of a sinusoidal waveform.

15
Dual Resonant Solid State Tesla coils / Re: My first DRSSTC on bricks
« on: April 08, 2019, 08:21:27 AM »
Good progress on the coil and inverter, this really shows that if you pay enough attention to the brigde design and making it as compact as possible and with good snubbering, the resulting waveform show it was not in vein, good job.

Netzpfuscher: There is a lot of good trouble shooting and background information about UD3 in this thread, maybe make a FAQ in your own original post with a copy of these answers? Or just a link to different threads where it is dicussed?

16
Beginners / Re: TVS Diode Questions (Rule of thumb maybe?)
« on: April 03, 2019, 01:47:01 PM »
Steve Ward wrote a little passage about this on his website: http://stevehv.4hv.org/drsstc_design.htm

Quote
Use Transient Voltage Suppressors (TVS) from collector to emitter of each IGBT.  The TVS should typically be the 1.5kW type.  I use strings of the 1.5KE220CA seriesing up as many as needed.  They are rated to stand off 220V, so for 600V IGBTs I use 2 in series.  For my 1200V IGBTs I use 4 in series for 880V clamping.  Note that the TVS do not start to clamp "hard" until you exceed their voltage rating by some %, check the spec sheet for the exact breakdown voltage.  Keep the TVS physically very close to the IGBT terminals.  The TVS are there to catch the very fast transients that the decoupling capacitors may not catch.  IGBTs do not tolerate overvoltage very well at all!

Use TVS or zeners on the IGBT gates.  If there is a voltage transient across the C-E junction, and the gate has some capacitance with respect to the collector, this transient will appear on the gate as well (its capacitively coupled through).  I use 30V TVS of the 600W type.  Be sure to get the bi-polar TVS.  Since we are driving the gates at their limitations, we need to be extra careful not to damage them, so TVS or zeners go a long way to protect them.

17
Solid state Tesla coils / Re: New small SSTC
« on: April 02, 2019, 12:21:17 PM »
Thank you!
Why the base current feedback not work with DRSSTC?

First of all I will test this minitesla, and then I try to implement a DRSSTC with the same secondary to compare the performance :)

I hope that in the next day arrives the wire so I can start to build the tesla.

You do not use the feedback in a DRSSTC to tune the driving frequency to match the secondary circuit, you manually tune a DRSSTC with moving the tapping point for best performance.

You need primary current feedback in a DRSSTC to be able to limit the peak current with a OCD circuit and to obtain the best possible ZCS to lessen losses in the IGBTs.

18
Solid state Tesla coils / Re: New small SSTC
« on: April 01, 2019, 10:43:53 PM »
It is possible to trasform this mini-tesla in a DRSSTC by adding a capacitor in parallel to the primary?

Now I have ordered the material necessary to build this little tesla. ;D

Secondary base current feedback for a DRSSTC was never a success, as you need as close to perfect primary circuit feedback as possible to avoid blowing up your silicon.

Let this circuit be a low voltage SSTC and if you want to build a simple DRSSTC, look at Steve Wards universal driver 1.3b to start with.

19
Electronic circuits / Teardown of a GE LP-33 10kVA UPS system
« on: March 31, 2019, 10:32:18 PM »
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A teardown of a General Electric LP-33 10 kVA UPS, a run down of the current paths in the system and I show which parts I brought home with me.

Datasheet on the unit: https://apps.geindustrial.com/publibrary/checkout/GEA-D1026?TNR=Data%20Sheets%7CGEA-D1026%7CPDF&filename=LP%2033%20-%2010-120kVA%20-%20CE%20Listed%20-%20Customer%20Data%20Sheet%20-%20GEA-D1026.pdf

20
Great results for a compact HV transformer like that, home printed bobbin as well?

How much power is it consuming here? Some 2-3 kW?

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