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Messages - Mads Barnkob

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1
Dual Resonant Solid State Tesla coils / Re: CM300 coil build questions
« on: September 20, 2019, 08:06:32 PM »
The datasheet for the Mitsubishi CM300DU-24H's only specifies Vge as +/-20V, so I'm already exceeding that by using a 24VDC supply and driver. The undershoot was there even without anything on the bus, though some of my scope shots makes it look a lot less at higher voltages on the bus. As I've noticed, others are driving CM300s in a similar fashion with similar undershoots without issues. I have plenty of spare silicon, so I think I'll let it rip and see how it fares. The UD2.7C doesn't have any dead time functionality, so I think I'd rather er on the side of caution. And because it's a pain to get to the gate connections without disassembling half the bridge... Something I want to address in the future.

http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/igbts/

Maximum Gate-to-Emitter Voltage (VGE)

The gate voltage is limited by the thickness and characteristics of the gate oxide layer. Though the gate dielectric rupture is typically around 80 volts, the user is normally limited to 20 or 30V to limit current under fault conditions and to ensure long term reliability.

It is normal practice to drive IGBTs at +24VDC with the Steve Ward universal driver and clones of it that most use. The reason for the gate voltage limit is not so much for protecting the gate itself, it will first break down at some 80 Volt. Higher gate voltage means higher currents can be conducted through the Collector-Emitter. We take advantage of this by pushing the gate a little over its rated voltage to allow us to conduct higher currents through the IGBT, at the cost of higher switching losses. As explained by manufacturers in the following.

It is important to note however that IGBTs exhibit relatively high gain even at high gate-emitter voltage. This is because increasing the flow of electrons by increasing the gate-emitter voltage also increases the flow of holes. The gain of a high voltage power MOSFET however is very insensitive to gate voltage once fully on.

2
Dual Resonant Solid State Tesla coils / Re: CM300 coil build questions
« on: September 19, 2019, 09:49:15 PM »
It is a very nicely built coil you have there, that bridge layout and compactness, can not get much lower inductance than that!

Congratulations on your first light!

Regarding the negative peak on the gate signal, maybe its inherent for the steve ward UD? Are all gates the same? To rule out its something like voltage drop on the DC bus negative rail or some weird crosstalk from the inverter driving a load.

3
Laboratories / Re: The new toy
« on: September 19, 2019, 09:13:29 PM »
Very nice, it is a power house and practically indestructable!

I got a 3 phased version of almost the same, 3x25A variac with motor control.

Never used it :o and it is super heavy!






4
I hope Hydron will see this thread and give his experiences with USB oscilloscopes, as I never owned one. I never dared due to the low performance / cost, when compared to Rigol etc.

Here is a nice little quick guide to buying oscilloscopes that explains 12 important points, really 3 of them is the most important as a lot doesn't make sense for a USB oscilloscope and at lower bandwidth, bandwidth is desribed at #1: https://www.mouser.com/pdfdocs/Tektronix12_things_to_consider1.pdf


5
Dual Resonant Solid State Tesla coils / Re: CM300 coil build questions
« on: September 18, 2019, 01:35:58 PM »
The GDT waveform is perfect, if it wasn't for the massive undershoot, I get a feeling its related to your 1N5819 schottky diode in parallel for fast turn-off, have you tried to remove it?

Your switching waveforms look fine aswell, do not get scared by the large switching spikes when doing a low voltage test. The output capacitance of the IGBT is larger at lower voltages and thus you will see % ratio larger switching spikes at lower voltages than when you get up at full input voltage. So if you see 50% spikes at 60VDC, do not fear/expect 900VDC spikes at 600VDC in, it will properly be around 10-20% spikes.

Just test with highest possible supply voltage and start out with a very low BPS, like 1BPS and see how it goes. It is better to test at full voltage and just lower BPS, even if there is something wrong, a IGBT brick is specified for high short circuit currents for 1ms, so a single pulse of 200uS high current is not enough to harm the die from too high temperature rise.

Please do post more pictures of the bridge, coil and everything else related to this build :)

6
I assume you have this at home, do you know what computer it came from and do you have any other related parts?

Core memory history is really interesting as it was a leap in computation speed due to faster access times to data and just the shear power consumption reduction durings development shows a will to make it cheaper, smaller and more usable in all kinds of machines besides large main frames. https://en.wikipedia.org/wiki/Magnetic-core_memory

7
Electronic circuits / Re: Offgrid 48V solar to 24V battery setup
« on: September 16, 2019, 09:40:27 AM »
In part 4 I take a look at the efficiency and look at the performance over the last 60 days


8
Dual Resonant Solid State Tesla coils / Re: My second DRSSTC
« on: September 16, 2019, 09:28:43 AM »
Erdal, that is a solid MMC design and snubber capacitors are perfect for MMCs, good that you could find those cheap. There is not a thing to put a finger on :)

New topload dropping Fres to 80kHz, I would say you could push those CM300 to 1kA if you feel adventurous, you even have a little head room for it on the MMC!

Another thing, all your tinypic pictures have stopped working :( You should really upload all your pictures directly on the forum, then it will work "forever" and not loose link to some online 3rd party gallery

Davekni, he simulation you see is from JavaTC, the worlds best online Tesla coil calculator, there is a link to it, among other calculators here: https://highvoltageforum.net/index.php?topic=573.0

9
Transformer (ferrite core) / Re: Large Ferrite Core with IGBT-Brick Driver
« on: September 16, 2019, 09:24:17 AM »
Wow, a very impressive project!  I do have two questions:

1) Is 3-phase power normal for residences in Austria (I that's where you are)?  It's certainly not here in USA - only available in commercial buildings.
Thank you for sharing your project!

3-phase 400VAC is normal in almost all of Europe, in households, we use it for oven, stove, washer, dryer etc. and can also install 3-phased industrial loads, it is nice!

In Denmark a normal house hold is 3x 400VAC @ 25A from the fuse box at the road.

10
Dual Resonant Solid State Tesla coils / Re: Transistors good for DRSSTC?
« on: September 12, 2019, 11:07:39 AM »
While they do look interesting to use in 120VAC countries there seems to be more cons than pros, simply due to the IGBTs getting destroyed from heat.

The 500Apeak rating is only specified for 10uS pulses
The legs are derated to a mere 75A

It is worth looking into paralleling these, obvious nice looking specs are gate charge, switching speed and Vce(sat)

I would worry the most about the Fmax2 calculation due to thermal limitations on this part, guide to calculate Fmax2: http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/igbts/

11
General chatting / Re: "karma", "applause/smite" button meaning and use
« on: September 12, 2019, 11:01:05 AM »
I was looking for a plugin similar to reddit style where a post gets rated for its value, this is not really possible to do in a classic forum setup like SMF.

So I tried out the karma system and it is just a global user bound system, so if someone liked your post and give you a karma+, it just shows your total everywhere, its not thread/post related.

It should be seen as a "quality" measure, so that post count is not a single measure of how much a person contributes.

It was put in a trial and I would gladly put up a poll to get some feedback on it

12
Electronic circuits / Re: I need a developed circuit for induction heater
« on: September 10, 2019, 09:14:17 PM »
Clearly the warning in another thread was not understood. Thread locked.

You can google "mazilli induction heater" or buy a induction heater on ebay.

This forum is not the place to ask for full instructions, schematics etc. without showing a effort to find the information yourself.

13
You need to read the forum rules: https://highvoltageforum.net/index.php?topic=31.0

You have started a few threads now, in clear violation of rule #2, please consider your future threads and posts carefully before pressing submit.

This thread is closed and you are welcome to start a new once you have done your own research, know a bit more about the difference between maximum current, constant current or current limiting.

14
General chatting / Re: The effects of the high voltage arces
« on: September 10, 2019, 07:18:26 PM »
Quoted from: https://www.pupman.com/safety.htm

Quote
4.0) Ozone, NOx, and Vapors
A sparking tesla coil produces ozone, nitrogen-oxygen compounds, and probably a host of other potentially toxic substances. Do not operate a large coil in an enclosed area for long periods of time. Make sure ventilation is adequate at all times. There have been anecdotal references to people becoming ill due to ozone toxicity. The long term bioeffects are unknown.

Personal experience from operating Tesla coils indoor and breathing too much of a badly ventilated air results in a solid head ache.

15
Static electricity / Re: Using static electricity in the car painting
« on: September 10, 2019, 08:27:07 AM »
Do not mix home made high voltage and normal volatile combustible gasses like a spray paint would be!

Electrostatic powder coating, where you need an oven to melt and harden the particles into a paint layer, could be done safely at home, but I doubt you have an oven.

I would advise you to buy a DIY cheap electrostatic spray painter kit, as you will only get good results if you have the right tools anyway.


16
Solid state Tesla coils / Re: SSTC not getting interrupted
« on: September 09, 2019, 03:29:32 PM »
It seems like they are getting discontinued, so it is also better to find alternative ICs that has the same/almost the same pinout and same specifications and adopt the UD designs to these.

Even digikey can only deliver at a 200 piece minimum order :( https://www.digikey.dk/product-detail/en/texas-instruments/UCC27321PG4/UCC27321PG4-ND/1911356

17
Radio frequency / Re: ZTE Communication Board
« on: September 09, 2019, 02:57:56 PM »
I am not a RF or base station /cell site specialist, but I have taken apart and done teardown videos on about 10-15 3G/4G systems.

Normal supply voltage for this radio gear is 48VDC, some times it is grounded and other times its floating, not connected to the chassis ground. Your best bet is to reverse-engineer the tracks back from the local power supplies at the FPGAs back to the connector. If you are unlucky, then you need some enable signals buried somewhere in the small pins in the middle.

Generally I have found that there is very little information available on ICs inside these systems, a lot of it seems to be special product numbers or whole series of ICs that has no reference to any publically known components.

18
Solid state Tesla coils / Re: SSTC not getting interrupted
« on: September 09, 2019, 10:02:25 AM »
There is a logic table on page 14 here that shows you the combination of enable and IN to your OUT: http://www.ti.com/lit/ds/symlink/ucc27321.pdf

I have previously experienced that non-grounded / unused / floating input pins on ICs can make a SSTC run in continues mode, simply due to interference from the magnetic field of the secondary coil.

19
The larger the Tesla coil / topload is, the more you need a larger diameter break out rod to prevent corona losses.

I am planning to make some aluminium tubing at maybe 30-40 mm diameter, with a brass insert that can hold a tungsten rod for tig welding with a set screw, that should take care of the corona and wear on the break out point tip due to heat.

20
Wow!  :)

Just a questions, where do you get all of that RF equipment? Is it part of your job? Are they defective, or just out of service?

Regards

I find it as scrap metal, it is sold off for its large quantity of aluminium and gold plated electronics. It is not a part of my job and I am pretty sure they are just taken down due to upgrades. Even though these LTE (4G) capable amplifiers could be used for 4G instead of the 3G they were running, its not a viable option as they need to combine their amplifier outputs for 4G, so a single amplifier can no longer run a 3 zone antenna, so its cheaper to just throw them out and buy a new 4G/5G amplifier that can work with 3 zones.

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