Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Messages - Mads Barnkob

Pages: [1] 2 3 ... 64
1
General Chat / Re: Corona lockdown thread, tell about your situation
« on: April 04, 2020, 11:15:57 PM »
We are still below 200 dead _WITH_ corona. No official numbers say that anyone died from it, but there is so many dead that had the virus. This is due to the issues with many being very sick in the first place.

Number of people in ventilators went down.

I spoke to a couple that live nearby me, husband was just home from hospital, he was in with corona and his story about being completely drained, not even able to crawl is frightening. It goes very fast from the first symptoms and fever and the next day you might not even be able to get yourself help, if you are alone.

I starter spring cleaning my work shop and found a lot of stuff that I had forgot about, sorted stuff in boxes together and is finding "right" places for it all :)

Fuses is day 24 topic.


2
Beginners / Re: A few (stupidly basic) questions
« on: April 03, 2020, 02:20:07 PM »
Mads,

Isn't SSTC frequency determined by the secondary and top-load?  So the 250kHz example in your design guide would remain constant, not go up to 1MHz.

I mistakenly took that as a DRSSTC example with seeing it all to have one resonant frequency. What a nice blunder  ::)

One point I forgot to mention for scaling voltage: primary geometry.  To scale properly, the primary winding needs to remain the same size.  For scaling from 320V to 80V, the primary in your example needs to be four paralleled 2-turn windings to fill up the same vertical height.  To keep wiring inductance low enough, each two-turn winding would need to route down to the H-bridge separately, ideally as four twisted pairs.

The above primary winding should have 1/16th of the inductance (same geometry, 1/4 turn count), or 635nH, for 1.0 ohms at 250kHz.  That's 80 amps at 80 volts, for the same reactive power as 20 amps at 320V.

For the above comparison, I've used the calculations as they are on your SSTC design guide.  However, the actual peak currents are higher, since square waves have more area than sine waves.  The current through an inductor with square-wave voltage is a triangle wave.  For 250kHz and 320V, the coil sees +320V for 2us.  That ramps the current through a 10uH inductor from -32A to +32A (640uVs).  The peak current is 32A.  Of course, this is with ideal assumptions - no coil resistance and no H-Bridge switching transition time.

Separately, I like the nice picture in your SSTC design guide showing the tight coupling of primary coil to the bottom of the secondary coil.  That prevents that lower secondary portion from building up even higher voltage due to resonant current, since that voltage is tightly coupled to the primary's fixed voltage.  (I had been wondering about how the physical proximity didn't cause breakdown issues, until realizing that it also clamped the lower secondary voltage.)

You are right about the, in theory, reactive power that should be the same.

But I have yet to see a low voltage SSTC with the same performance. I am unsure if its down to the, very unscientific saying, "more voltage is more better" when it comes to resonant voltage rise or you can substitute that with longer on-times. Maybe it is because the designs was not built to match the same reactive power due to high current requirements where sourcing the 100A+ becomes more of a hazzle and the power supply/transformer begins to dwarfen the coil it should drive.

One of the most famous 24VDC SSTC is the Skori II mini SSTC: http://skory.gylcomp.hu/tesla/mini_tesla2.html with 100A MOSFETs and forced air cooling on the primary :) Maybe it just gets way too impractical to match a mains fed coil if you try to scale that up.




3
DSLR / Re: Photographing/filming high voltage arcs
« on: April 02, 2020, 11:48:01 PM »
You need to shoot in manual mode, manual focus as well, on tripod/support.

For good arc pictures, long exposure like 1-2 seconds can capture several strikes in one picture.

If you link some specific pictures, I can tell more in detail about that situation :)

4
General Chat / Re: Corona lockdown thread, tell about your situation
« on: April 02, 2020, 09:27:50 PM »
It seems I have forgotten to post the last couple of days videos. So here comes day 20, 21 and 22!

This also concludes the daily videos, I have run out of things to show :)

Day 20
/>
Day 21
/>
Day 22

5
Beginners / Re: A few (stupidly basic) questions
« on: April 02, 2020, 02:53:24 PM »
Mads,

I'm curious about your line: "I have only built mains powered SSTCs as I find the low voltage versions to be harder to get to work and they also seem to have lower spark-length-efficiency, I am a sucker for long sparks".  If the power levels are equivalent and the part impedances are all scaled appropriately (larger capacitors, lower inductances, etc.), what makes the difference?  The best guess I'd have is that wiring inductance through the primary circuit (H-Bridge to primary coil) isn't reduced enough.  Low impedance would require twisted pairs and tight layout.  Do you have other possible reasons?

Thank you.

I wish I had the time to do the math, so here I just try with some quick figures. http://kaizerpowerelectronics.dk/tesla-coils/sstc-design-guide/

60VAC ~80VDC, around 4 times lower than 320VDC.

Removing 6 turns, so we are down at 2 turns. 25% less inductance and we get the same primary reactanse. 16 Ohm.

But then primary current is still only 5A instead of 20A, since voltage is still lower, so we need to lower the primary reactanse further, but then the frequency rise again. Already being at 1MHz, I think its no longer a optimal route to follow. At least not to expect same performance as with mains powered.


The above was wrong for a SSTC as it assumed secondary circuit to change frequency.


6
Beginners / Re: A few (stupidly basic) questions
« on: March 31, 2020, 08:54:35 AM »
Welcome to HVF :)

Safety
In the high voltage hobby, I find it much more life prolonging to view everything as live if it is not grounded. This way there is no questions about what is safe, what can I touch if the voltage is low enough, if its isolated, if its floating, one hand on the back etc.

Accept that everything is dangerous, even low currents at seemingly low voltages can stop your heart if it hits you at the right time in the cardiac cycle.

Adapt your work habits around this philosophy and you will never find yourself in a dangerous situation. Learn to make things safe by design. Now I do not want to sound as a saint, a quick glance on my website shows I have not always done this. But I have learned a lot and still have a lot to learn about safe by design.

EMI... Most of the energy should get dissipated in the spark itself, as it is your load. I have experienced that a 300 kHz SSTC can lay down ADSL modems, as the upload band of ADSL is just in that range. I also wrote some about all this in this article: http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/grounding-circuit-protection-and-emi/ which should answer all your questions about EMI.

SSTC
A SSTC is not directly drawing the current from mains to the primary coil, you have a DC bus capacitance to deliver peak current in the middle. That being said, the primary circuit current is close to what you can pull fro your mains, you still have to charge those capacitors. With interrupters you are able to deliver higher currents, but maybe only 200 times a second, this is done to get around the mains power limitations and to stress the switches less to give them time to dissipate the switching losses.

I wrote a short SSTC design guide here: http://kaizerpowerelectronics.dk/tesla-coils/sstc-design-guide/

I have only built mains powered SSTCs as I find the low voltage versions to be harder to get to work and they also seem to have lower spark-length-efficiency, I am a sucker for long sparks :)

It is good that you have a variac, oscilloscope and some parts. I really recommend that you build something like the Steve Ward Mini SSTC, it can both be half- or full-bridge. It is simple, few parts and it will also explode once in a while due to slack antenna feedback control :) But once you get some high voltage experience with a SSTC, you can easily move into DRSSTC topologies and gain the benefits of stricter control.

A variac is crusial to slowly ramp up voltage, notice if there is sparks or flash-overs where there shouldn't be, then go to full voltage. Once the Tesla coils bridge explodes, repair it and turn the variac 20% down :) Always keep in mind that much of the Tesla coil design theory is with +/- 3dB due to many assumptions and experimental models.

Start out with some cheap IRFP460 MOSFETs (or a better more modern alternative with about the same ratings). Build a SSTC: http://kaizerpowerelectronics.dk/tesla-coils/kaizer-sstc-ii/

If you can afford it, get a differential probe, important tool to have when working with inverters. To avoid damaging your oscilloscope or short circuiting your inverter through your oscilloscopes ground path.   

7
General Chat / Re: Corona lockdown thread, tell about your situation
« on: March 30, 2020, 08:08:54 PM »
Latest messages from the government is select few, partial opening in 2 weeks, if numbers stay "linear" for the next 2 weeks. Only time will tell what happens.

Day 19 in isolation topic: IEC and CEE plugs for high power single and three phase connection of equipment. I do a rundown of old, new and special connectors and plugs used in Europe. Ranging from 230V 10A to 400V 63A.


8
Thank you Dave :)

I still think you have a problem with smashing those IGBTs with way too much RMS current, I really encourage you to do the Fmax2 calculations and you will see exactly if you are misusing them or not. How about them being "fakes" or 2nd, 3rd and even "bad" batches that did not meet factory standards and was sold out the back door?

If you suspect the driver to be the problem and there is little to no help in the translated manual, you should spend a few days to build a UD2.1b, you can even do this with single side components all they way: http://stevehv.4hv.org/leadcomp/UD2_1revB/

I used output MOSFETs are IRF540 and IRF9540. http://kaizerpowerelectronics.dk/tesla-coils/kaizer-drsstc-iii/

9
Similar "400A" rated IGBT bricks have been pushed to 1300A in reliable operation. So 800A is certainly nursing them :) I think you could push it to 1000A and still be playing it safe. Depends on your MMC design if the resulting higher voltage and current is still within the limits of it.

See the table for IGBT proven speeds/currents at bottom of article here: http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/igbts/

10
I found it on page 2 : https://highvoltageforum.net/index.php?topic=959.msg6538#msg6538 you are right, you mentioned it at the bottom of the post. This is why I prefer all details are given in the original post, looking through pages of thread for all the basic details is hell.

Paralleling IGBTs is not the same as doubling their current rating! For reliable operation you should never assume that they can handle more than 50% more. You need to match the IGBTs, have them on same heat sink, be sure their gates are driven identically etc. if you want to break that figure. All the figures in a IGBT datasheet is given for hardswitching, you can not use any of those numbers for current, losses or frequency for a softswitching Tesla coil, you have to calculate that yourself.

What is your OCD set at? 5V? it was just an example I have on the UD2.1b as it uses 5V on the op-amp. Did you test your OCD input with a frequency generator?


11
General Chat / Re: Corona lockdown thread, tell about your situation
« on: March 29, 2020, 10:04:21 PM »
We are now looking at 500 hospitalized, 100+ in intensive care, 70+ dead and government still expect this to first top in 2-3 weeks. No plans for unlocking yet.

Day 18: Over the years I have collected a great deal of salvaged #IGBT bricks from the different power #electronics I have taken apart. It have primarily kept 50+ Ampere rated bricks, single or half-bridge modules and 3 phase modules without builtin protection. It mostly comes from UPS, motor drives, welders or x-ray generators. #teardown


12
First some props to Davekni, you put a good amount of time into helping people! 8)

Should I lower the overcurrent? I have it set at 500A right now. I'm using 8 IGBTs in total, so it should work (each of them is rated for 225A pk in the datasheet)

I have never had success with pushing TO-247 packages to 500A, what IGBTs are you even using? Did we make it to page 5 without a part number? Did you do any calculations on the IGBT you are using, like looking at Fmax2 using my guide? http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/igbts/

Could it have been overcurrent? I think the current rises quite a bit when the secondary shorts. I've heard the OCP might be slow and take a few cycles to actually trigger. In that case 500A might be too high.

Also, for my next project, I might use the 120N60 IGBTs, which seem to have 600A peak current in a TO264 package. Would this work? Here's the datasheet: https://www.mouser.com/datasheet/2/240/Littelfuse_Discrete_IGBTs_PT_IXG_120N60B3_Datashee-1591813.pdf

OCD/OCP, if a exact copy of the Steve Ward design, has to use a CT+shunt resistor where you get a voltage for your limit around 2.5V If you get out to the boundaries of the op-amp, like setting your potentiometer to 5V reference for the maximum OCD current, you have basically disabled the OCD as there is no working range for the op-amp anymore.

The 120N60 looks like a re-packaged ISOTOP IGBT, properly same die size, I would not expect this to do much better than a TO-247 part. I would think the limit of this package is still 500Apeak. But do the math, calculate Fmax2!

13
A very rare conical coil, I heard they were such a pain to wind that I never tried it :) How was your experience with slipping wire and did you start from the top to let it slip up against that turn?

Looking forward to see the specs, I was just wondering if 2x 2200uF is enough bus capacitance for pulse skipping without serious dc bus sagging?

You also printed a lot of parts for this coil, my favorites are by far the "square-aluminum-bar-to-wood" adapter for fastening the primary platform with! Did you share your models on some 3D printer websites?

14
General Chat / Re: Corona lockdown thread, tell about your situation
« on: March 28, 2020, 10:27:34 PM »
Day 17


15
General Chat / Re: Corona lockdown thread, tell about your situation
« on: March 27, 2020, 07:53:38 PM »
It is starting to feel like it :)

This video is together with my son, as day care is shut down as well.

I show a range of different industrial components that you can salvage from thrown out machines, main breaker panels, x-ray and UPS systems. Look at privately owned scrap yards and metal recyclers in your area to get the same opportunities to find stuff like this, be prepared to pay per kg for some of the stuff that contains large copper pieces like the big contactors or transformer scrap price for the filters. Overall it is still a very cheap way to obtain expensive parts.


16
General Chat / Re: Corona lockdown thread, tell about your situation
« on: March 26, 2020, 08:56:22 PM »
Day 15.

Not completely insane yet, but here is some electrolytic capacitors


17
Solid State Tesla Coils (SSTC) / Re: Popped my first pair of IRFP460's
« on: March 26, 2020, 06:56:13 AM »
I concur with Weston. You are on the brink of breaking forum rules with such a short, non-informative and asking straight for instructions post.

I will give you the chance to add more information, as you do have a coil built by yourself, that you want to troubleshoot on.

So please go ahead and supply all design details, detail pictures, numbers, calculations, how you ran it at time of failure etc.

Else the thread is subject to be closed.

18
Beginners / Re: Why is Auto-transformer (variac) called transformer??
« on: March 25, 2020, 06:04:16 PM »
There is 3 variations that are commonly mixed up when people talk about variac, autotransformer, variable transformer, isolation transformer etc.

Autotransformer


Variable (isolation) transformer


Variac / variable autotransformer


From: https://www.allaboutcircuits.com/textbook/alternating-current/chpt-9/winding-configurations/

Also from wikipedia: https://en.wikipedia.org/wiki/Autotransformer

Quote
An autotransformer is an electrical transformer with only one winding. The "auto" (Greek for "self") prefix refers to the single coil acting alone, not to any kind of automatic mechanism. In an autotransformer, portions of the same winding act as both the primary winding and secondary winding sides of the transformer. In contrast, an ordinary transformer has separate primary and secondary windings which are not connected to each other.

Quote
Variac Trademark
From 1934 to 2002, Variac was a U.S. trademark of General Radio for a variable autotransformer intended to conveniently vary the output voltage for a steady AC input voltage. In 2004, Instrument Service Equipment applied for and obtained the Variac trademark for the same type of product.[7] Instrument Service & Equipment reserves all rights of use of the trademark VARIAC for variable transformers and related devices.

19
General Chat / Re: Corona lockdown thread, tell about your situation
« on: March 25, 2020, 12:40:45 PM »
Ah that's a bugger, there is a lot of spectacular scenery they missed after W(h)anganui, especially in the south island. Hope they made it home OK, though it does seem like a bit of "out of the frying pan, into the fire" going back to the states right now given the numbers there (assuming that's where they are going to?).

Danish goverment recommend returning home, to ensure you have the best possible healthcare available as a citizen (for free in Denmark), it can get real expensive or be on subpar hospital / get behind in the queue if you are stuck in another country and you get sick. Language barriers, insurance claims, legal stuff etc, it is just easier to be sick at home :)

20
Good to see that you have it all running and making sparks. Good first and second tests at lower voltages, I am looking forward to see you run the coil at full voltage and maximum on-time :)

Did you get some optimization done? Like that very long primary lead, that could be much shorter. But overall your setup looks very clean and well designed.

I can read German, so I would like to see you documentation if you still want to share it.


Pages: [1] 2 3 ... 64

* Recent Topics and Posts

post Re: First Medium DRSSTC Build with Updates
[Dual Resonant Solid State Tesla coils (DRSSTC)]
zanikk
Today at 12:43:24 AM
post Re: Corona lockdown thread, tell about your situation
[General Chat]
Mads Barnkob
April 04, 2020, 11:15:57 PM
post Powerful easy to build MIDI Interrupter
[Computers, Microcontrollers, Programmable Logic, Interfaces and Displays]
Max
April 04, 2020, 09:35:28 PM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
April 04, 2020, 08:01:11 PM
post Re: IGBTs dying silently, but why?
[Dual Resonant Solid State Tesla coils (DRSSTC)]
xxThorx
April 04, 2020, 04:07:16 PM
post Re: Power MOSFETs with fast recovery body diodes
[Electronic Circuits]
T3sl4co1l
April 04, 2020, 09:01:32 AM
post Re: Corona lockdown thread, tell about your situation
[General Chat]
johnf
April 04, 2020, 08:19:16 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ritaismyconscience
April 04, 2020, 05:37:11 AM
post First Medium DRSSTC Build with Updates
[Dual Resonant Solid State Tesla coils (DRSSTC)]
DJthefirst
April 04, 2020, 03:56:46 AM
post Re: DRSSTC design questions + project progress
[Dual Resonant Solid State Tesla coils (DRSSTC)]
Vaclav
April 03, 2020, 03:07:13 PM
post Re: A few (stupidly basic) questions
[Beginners]
Mads Barnkob
April 03, 2020, 02:20:07 PM
post Re: Class E SSTC Topology
[Solid State Tesla Coils (SSTC)]
ZakW
April 03, 2020, 07:26:37 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ritaismyconscience
April 03, 2020, 04:27:08 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
April 03, 2020, 04:21:56 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ritaismyconscience
April 03, 2020, 03:49:51 AM
post Re: Photographing/filming high voltage arcs
[DSLR]
klugesmith
April 03, 2020, 03:09:17 AM
post Re: Photographing/filming high voltage arcs
[DSLR]
Mads Barnkob
April 02, 2020, 11:48:01 PM
post Re: Class E SSTC Topology
[Solid State Tesla Coils (SSTC)]
ZakW
April 02, 2020, 11:02:29 PM
post Re: Class E SSTC Topology
[Solid State Tesla Coils (SSTC)]
Weston
April 02, 2020, 10:44:04 PM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
April 02, 2020, 09:45:03 PM
post Re: Corona lockdown thread, tell about your situation
[General Chat]
Mads Barnkob
April 02, 2020, 09:27:50 PM
post Re: A few (stupidly basic) questions
[Beginners]
davekni
April 02, 2020, 08:58:12 PM
post Field Mill
[Static Electricity]
haversin
April 02, 2020, 08:46:26 PM
post Re: A few (stupidly basic) questions
[Beginners]
Uspring
April 02, 2020, 08:41:49 PM
post Re: Fishing for atmospheric electricity
[Static Electricity]
haversin
April 02, 2020, 08:25:29 PM
post Re: Power MOSFETs with fast recovery body diodes
[Electronic Circuits]
johnf
April 02, 2020, 08:24:07 PM
post Re: TVS diode selection for 400v transistor
[Electronic Circuits]
davekni
April 02, 2020, 08:20:25 PM
post Re: (DR)SSTC music MIDI files
[Dual Resonant Solid State Tesla coils (DRSSTC)]
DJthefirst
April 02, 2020, 08:20:07 PM
post Re: Power MOSFETs with fast recovery body diodes
[Electronic Circuits]
davekni
April 02, 2020, 08:09:29 PM
post Re: A few (stupidly basic) questions
[Beginners]
Mads Barnkob
April 02, 2020, 02:53:24 PM
post Re: A few (stupidly basic) questions
[Beginners]
John123
April 02, 2020, 11:46:07 AM
post Re: TVS diode selection for 400v transistor
[Electronic Circuits]
John123
April 02, 2020, 11:40:55 AM
post Re: Power MOSFETs with fast recovery body diodes
[Electronic Circuits]
John123
April 02, 2020, 11:32:19 AM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
ritaismyconscience
April 02, 2020, 03:48:55 AM
post Re: Class E SSTC Topology
[Solid State Tesla Coils (SSTC)]
ZakW
April 01, 2020, 09:47:42 PM
post Re: GDT keeps on killing IGBTs
[Dual Resonant Solid State Tesla coils (DRSSTC)]
davekni
April 01, 2020, 09:31:49 PM
post Re: Power MOSFETs with fast recovery body diodes
[Electronic Circuits]
davekni
April 01, 2020, 08:47:11 PM
post Re: Fishing for atmospheric electricity
[Static Electricity]
johnf
April 01, 2020, 08:45:14 PM
post Re: Homemade HV transformer
[Transformer (Ferrite Core)]
johnf
April 01, 2020, 08:37:29 PM
post Re: TVS diode selection for 400v transistor
[Electronic Circuits]
davekni
April 01, 2020, 08:24:06 PM
post Re: Pt100 oddities
[Electronic Circuits]
davekni
April 01, 2020, 08:16:59 PM
post Re: Pt100 oddities
[Electronic Circuits]
johnf
April 01, 2020, 07:50:16 PM
post Re: Fishing for atmospheric electricity
[Static Electricity]
haversin
April 01, 2020, 07:42:47 PM
post Re: Homemade HV transformer
[Transformer (Ferrite Core)]
John123
April 01, 2020, 07:39:48 PM
post Re: Fishing for atmospheric electricity
[Static Electricity]
John123
April 01, 2020, 06:07:44 PM
post Photographing/filming high voltage arcs
[DSLR]
John123
April 01, 2020, 05:17:04 PM
post Power MOSFETs with fast recovery body diodes
[Electronic Circuits]
John123
April 01, 2020, 02:01:30 PM
post Re: Pt100 oddities
[Electronic Circuits]
kamelryttarn
April 01, 2020, 01:38:47 PM
post Re: Pt100 oddities
[Electronic Circuits]
T3sl4co1l
April 01, 2020, 12:49:21 PM
post Re: TVS diode selection for 400v transistor
[Electronic Circuits]
John123
April 01, 2020, 10:29:06 AM

SimplePortal 2.3.6 © 2008-2014, SimplePortal