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Messages - Mads Barnkob

Pages: [1] 2 3 ... 56
1
Solid state Tesla coils / Re: Performance Issues in SSTC
« on: October 09, 2019, 09:12:47 AM »
Did you try to switch the primary coil wires around, in order to reverse the primary phasing?

You might be switching on a out-of-phase feedback signal and that would explain that it works with antenna really close, it is simply shoot-through, leakage and capacitively coupled energy through the system that gives a small spark.

2
Dual Resonant Solid State Tesla coils / Re: Problems with my first DRSSTC
« on: October 09, 2019, 09:09:19 AM »
It's weird that things get a little better when I touch one of the feedback inputs with a screwdriver  :o
What can cause this behaviour , driver , CT , GDT or something else?

It is clear that you have a too weak feedback when you can get better performance when using yourself as a capacitively coupled antenna on the feedback.

I would look at all components from feedback op-amp -> diodes -> CT

Did you rule out phase error? Reversing primary connections (remember to place CT on the low voltage end of LC circuit), phase of CT, phase of GDT. It is possible to get unstable operation when driving things off-off or out-of-phase just from the leakage energy through the system.

3
Dual Resonant Solid State Tesla coils / Re: Drsstc 3
« on: October 08, 2019, 12:22:54 PM »
Cheers,
Yes the tuning changed quite a bit, I think something like 18khz or more. I still have fine tuning to go. To be honest I'm not sure what it would normally pull before as I had the OCD set to 900a.

One thing I've been thinking about making is essentially a vu metre for current, have the leds in 100a steps 🤔

I actually made such in 2011 and never finished the project :o It was based around a cheap DMM IC called ICL7017 and a VU meter IC, guess microcontrollers like Arduino surpassed that project by now. But it was meant to just be a homemade CT and a 0-2000A display + VU meter.

4
Dual Resonant Solid State Tesla coils / Re: Drsstc 3
« on: October 07, 2019, 12:37:44 PM »
Nice sparks and also a nice looking coil, I am a total fan of secondary coil diameter and toroid topload minor diameter being the same!

You properly had to de-tune the primary some more? Noticeable enough to have higher peak current and thus getting longer sparks from a lower impedance system?

5
/>
I visited HI Tech & Industry Scandinavia 2019 in Herning, Denmark and while doing so I recorded clips of the most interesting robots, robotics, machines, vision, PLC and machine technology.

You can find booth exhibitions from Schneider Electric, Beckhoff, Flir, MakerBot, Wago, Rhode&Schwartz, Coherent and so on.

6
I sold it a few years later as it was rotting away outside

Did you ever have it up and running? 150kVA is about the size I would like to own, on a trailer, but it would have to be a more modern generator set to get down in size for being dragged by a normal car :)

It's not the same dorman as the cheapo shitty china replacement parts for cars, is it ?

I guess that the brand Dorman, which was once a British produced product, is today, as many other brands, just a shadow of itself and either has a complete different business case today or the brand was sold off to some large conglomerate to take advantage of a known brand name.

7
Dual Resonant Solid State Tesla coils / Re: Drsstc 4 (new direction)
« on: October 07, 2019, 09:20:41 AM »
Since you are not going to document all detailed calculations and drawings, at least take some pictures along the way and post those :)

A SKM400 bridge on a 1 meter resonator is still a pretty big coil, I would not call that "small simple" ;)

It is a pretty large bridge for such a secondary size, what kind of primary current are you aiming for? When you say 25A limit on the mains outlet, that means you are limited to 120VAC@25A? Even 3kW will get you some 2 meter sparks!

8
Solid state Tesla coils / Re: SSTC stopped working HELP
« on: October 07, 2019, 08:50:42 AM »
I agree with oneKone

It sounds like you have one half-/dead MOSFET in your half-bridge. So a small amount of energy is still being pumped/leaked into the primary circuit and it only takes a few Watt of power to make a secondary circuit light up a CFL.

It could even just be your driver circuit coupling energy through the GDT and power the primary circuit from there, I demonstrate that exact behavior in this video where there is no power on the bridge.


9


I think the sole reason for unstable induction heaters is due to people using too small power supplies, most likely iron core transformers that are way too small, it gets overloaded, pulls the voltage down or saturates the core and boom goes the MOSFETs.

 
I am not following, how do you saturate a transformer by overloading it , ie taking to much current?
I totaly agree that if to much power is drawn, the rectified voltage on the caps drops and this leads to a very unstable operation of a Royerlike circuit, not unlikely that the high/low Mosfet latchup and crossconduct.

What is a reasonable power supply then?

You are right, overloading the transformer secondary side has nothing to do with core saturation, I wrote some gibberish there.

Since the Royer is super power hungry and f.ex. a specified 2kW unit can also draw exactly that, with changing size work coil and work piece, the current can suddenly be much higher than you expected. I would say that just to be sure, 25-50% current head room is preferable.

However, you need more current head room the lower voltage you are operating at. A 12VDC supplied homemade Royer with IRFP250N would get unstable below 10VDC, so it is far more prone to failure than a 36VDC suppplied Royer circuit from China.

10
It is not as bright as arc-welding, I did some experiments with different grade welding glass inserts in front of my camera to better record arcs and arc explosions.

My conclusion was that the lowest grade, least shading glass, gave the best result. After all this is not our day job and we do not stare into a arc 8 hours a day.

Tesla coil sparks are even weaker and moving up into high speed filming the glass made it impossible to get enough light in.

11
Dual Resonant Solid State Tesla coils / Re: QCW Tank Capacitor Choice
« on: October 04, 2019, 11:17:45 AM »
Very nice list you made there Weston, thank you for sharing!

I also made a MMC similar to Steve Wards, round around a rod, if you scroll down to the following chapter, you can see pictures, here: http://kaizerpowerelectronics.dk/tesla-coils/kaizer-drsstc-iv/

Quote
6th October 2015

Construction of a very cheap MMC from capacitors that was bought from a 10$ ebay auction for 100x Kemet R474N247000A1K, rated for 900VDC 28 A peak and 4 A rms. A easy and uniform construction, with current sharing in mind, is to construct it around a round piece of wood or plastic tube.

The resulting MMC has a capacitance of 0.047 uF at 9000 VDC, 280 A peak and 40 A rms rating. Which is spot on for this coil to be running with design goal primary inductance of around 100 uH, 300 A peak, 5000 uS on-time and maximum 10 BPS.

12
Hello Mads.
  You did a very nice job of packaging your 1800 Watt ZVS induction heater.
I like your idea of the big DC relay.  That should make it easy to add PID temperature control some day.

Several other induction heater experimenters have complained about ZVS heaters, saying that they do NOT start up reliably.  I have never had this problem.  Why do you think they say this?

I, too have been trying to get steel hotter than the curie point.  The only time it has worked for me is when I insulate between the work and the inside of the work coil, and cover the work, too:

You can see the high temperature part of this video at about 20 minutes in.

Pete Stanaitis
---------------

I got compact, but that also comes with some compromises, I have to run it for a long while to know if I can keep the temperature down or it will run away :)

I think the sole reason for unstable induction heaters is due to people using too small power supplies, most likely iron core transformers that are way too small, it gets overloaded, pulls the voltage down or saturates the core and boom goes the MOSFETs.

For a PI control, I would not use a mechanical relay, but a solid state, a mechanical DC relay at this current would get worn out too fast.

What kind of insulation material did you use in that video?

Here is another try, just with horizontal instead to contain some more heat, accidentally melted some plastic on the enclosure from that :)


13
Sell / Buy / Trade / Re: WTB: Eurofarad SP2550 capacitors
« on: October 02, 2019, 10:04:06 PM »
CTR surplus doesn't exist on ebay anymore :( ( here is a old cache item description that leads to their closed shop http://vi.raptor.ebaydesc.com/ws/eBayISAPI.dll?ViewItemDescV4&item=381091010440&pm=1&ds=0&t=1474031005614 )

AFAIK, Kizmo on 4hv bought a lot of them, you can find him on the IRC chat, just follow the chat link up in the top menu to log in through a webclient

14
Test with using regular mineral wool for house insulation, to insulated the work coil in order to achieve higher steel temperatures.


15
Okay, I know this took forever from when I first mentioned it and till I put it all together last night :)

The 1800W IH is now boxed up with all power supplies, water cooling, foot switch, current meter and insulated work coil.


16
Dual Resonant Solid State Tesla coils / Re: Next Gen DRSSTC
« on: September 27, 2019, 11:41:59 AM »
Netzpfuscher, seems like I completely missed your update on the inverter :( Some days the amount of new threads and posts are running wild, but that is nice :)

Nice and solid design, where did you get the DC link capacitors? The blue current transformer is for 50 Hz input current measurement? I can barely read it, is it HIMA timers? Got them cheap somewhere or just at hand, only found only price and that was not low! How about the current rating of the soft-start contactors?

17
"came by" ?
Do you have government approval to bring that home? :)

Yes, I came by it in my work, belongs to a customer. So it was just some pictures taken out of interest :)

I do however hope to get parts from a different decommissioned 400KVA generator set, at another non-related site, there will be a video on that if I succeed in getting access to it.

18
/>
The high resolution pictures and circuit explanation in text are hosted on my website: http://kaizerpowerelectronics.dk/teardown/nokia-siemens-flexi-3x90w-fxeb-1800mhz-base-station-teardown-power-amplifier-part-2-of-2/

19
Electronic circuits / 50KVA generator on a 4 cylinder Dorman diesel engine
« on: September 26, 2019, 09:44:26 AM »
I came by a small emergency generator that has been in service and still is, for a atleast 50-60 years.

The generator itself is a Titan KĂžbenhavn 50 KVA 3 phase 380 VAC, 76 Ampere and the diesel engine is a British Dorman 4LBIII 4 cylinder engine, which was also used in large excavators at the time.

The control panel was upgraded once, from a purely mechanical control, to a phase lock controller, which is still pretty old by todays standards.


20
Dual Resonant Solid State Tesla coils / Re: Problems with my first DRSSTC
« on: September 25, 2019, 08:40:33 AM »
One more thought on possible issues with CT feedback not functioning:

(BTW, hopefully continuing my last reply isn't what is banned as double-posting.  I can't figure out how to edit my last reply.)

Do you have a bleed resistor across your primary MMC array?  If not, the UD2.7 could be driving the IGBTs to the state that has the same voltage as is left on the MMC array previously.  That would induce no current, so no signal to reverse the gate drive. (Which is one reason to prefer self-oscillating controller circuitry.)

David Knierim

A simpler and quicker fix for the MMC residual charge, is to place a 5-10K power resistor across the output of the inverter, this removed instability problems with my large DRSSTC.

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