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Messages - Mads Barnkob

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1
Thank you for the update :)
I've stumbled over the equation you used to calculate the power dissipation in the cap. I've tried to reverse engineer it and it looks, like it applies to the case of a single charge up of the cap. It, e.g., does not incorporate the burst length. Inside a burst the caps are charged and discharged a number of times.
I'd use

P = Irms^2 * ESR

where Irms is taken from Conners equation. In your example that would be for a single cap (13A)^2 * 0.005Ohms or about 0.8W. The according temperature rise of 9 degrees would barely fit into the "good" range of tolerable temperatures. That also matches the Irms spec of the caps.

When I looked into my MMC calculator code, I did notice that there was something wrong as there was no accounting for on-time, but was mere single pulse * BPS, I tried to understand how I came to that formula and my only explanation is a old excel sheet for SGTC, which also lacks accounting for on-time. I need to get both calculator and article corrected.

I follow your argument with the Irms and the rating of the capacitor, that makes sense that it will quite quickly get to operate at its maximum permissible hot spot temperature of 105 degrees Celsius, but that still seems a bit far from reality of what I have seen with that coil used in the example.

I also had some old WIMA white paper on dissipation losses that I tried to give a go, but its an even worse result. Maybe I am getting something wrong with the RMS voltage?
Xc = 5.05 Ohm
ESR = 0.005 Ohm
Tan rho = ESR/Xc
Watt = ((Vrms^2)*2*pi*70000hz*0.45uF*tan rho
C/W -> W/K = 1/11 = 0,0909
Temp rise =(((2000/1.41)^2)*2*PI()*70000*(0.45/1000000)*(0.005/5.05))/(1/11) = 4000~ degree Celsius



The calculation for the number of half cycles to obtain a given primary current disregards loading of the primary tank by the secondary and arc loads. The rationale is this: Each time the voltage across the primary tank jumps by a certain value (as caused by the bridge), then this value is added to the MMC peak voltage after a half cycle. The primary current calculated from this is always an upper limit. Ideally secondary and arc loading should limit primary current so that OCD shut downs (to prevent transistor and MMC overload) won't happen.

I will make that a primary explanation and selling point for that method, that it is a worst case scenario. That method is also in my view one that should give the most over-engineered MMC.

2
Dual Resonant Solid State Tesla coils / Re: My First DRSSTC
« on: December 12, 2018, 01:15:30 PM »
Congratulations on first light!

100A is pretty low for a DRSSTC and I would not expect much happenning at such a low energy, unless it was very long on-times in the ms.

It looks like your coil is VERY close to the metal sheet wall, be aware that this will affect the resonant frequency of the secondary circuit ALOT! You need it to have a certain amount of free space in order for the calculated frequency from f.ex. JavaTC to be true.

Your low performance could also be from bad tuning, which could be the above cause of that, else experiment some more with the tuning point of the primary coil and get some more current flowing :)

3
It has been a very long time under way with the next chapter to go in review and it is the widely sought for: MMC design and calculations

You can read the article at: http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/mmc-tank-capacitor/  and to see it, the password is "test".

The reason for the password is to avoid google indexing and random visitors reading it before it has been reviewed by people with experience in the field.

This is where I need your help, there is most likely some spelling errors, bad sentences, does-not-make-any-sense chapters or calculations errors. Please reply to this thread about such findings for a discussion about it.

4
Dual Resonant Solid State Tesla coils / Re: My First DRSSTC
« on: December 11, 2018, 09:13:49 AM »
Your waveforms does look fine for low voltage testing.  You even have quite low voltage switching spikes for just testing at 20VDC (or your oscilloscope is not fast enough to pick up the spikes!). Normally you would see very large switching spikes that are 200% of the input voltage, this is due to IGBT output capacitance being constant no matter the input voltage, so as the input voltage rises the spikes ratio to inverter output gets smaller and smaller.

If you are concerned about skew in your measurements, check out this guide: https://highvoltageforum.net/index.php?topic=111.0

5
Dual Resonant Solid State Tesla coils / Re: My First DRSSTC
« on: December 10, 2018, 12:25:15 PM »
I misunderstood the edit mark and thought it was a new problem you described :)

The buzzing and to some extend that you can also feel it on your smallest hair on the back of the hand is normal effect of switching high frequency current, it is much more audible than you really imagine. You will however not be able to hear it once you have sparks flying with a sound level approximately as a hovering helicopter.

6
Dual Resonant Solid State Tesla coils / Re: My First DRSSTC
« on: December 10, 2018, 09:18:24 AM »
It seems like half of you bridge is not switching properly.

So either you have a problem with the driver not outputting a good drive signal or 1-2 of your IGBTs are bad.

Try to switch the leads around from GDT to bridge, if the bad switching IGBTs move to the other pair, the problem is in your driver circuit and if it stays the same, its your IGBTs thats something wrong with.

Check gate resistors, diodes etc as well, they can also be damaged without exploding, f.ex. a gate resistor going half-open will have a very high resistance and it could look like what you are seeing.

7
Solid state Tesla coils / Re: First SSTC build, need help troubleshooting
« on: December 10, 2018, 09:13:37 AM »
Hey guys,

So I probed around my antenna and hex inverter. The first 2 attachments are waveforms on the diode side of c3. The last 2 are of the output of the inverter to the gate drivers. Im not 100% certain of the waveforms as the dso138 has fairly poor resolution. However, it does seem like there is a weak feedback issue with the antenna. 5th attachment is my antenna placement. Maybe it needs to be longer or shorter?

I am only driving the circuit with 20v dc and with the configuration of the halfbridge side, only putting 10v into the primary each cycle. Could the field being produced by the coil not have enough energy to bring the feedback up to 5v? Im worried about increasing the voltage as my transistors are extremely hot after a minute or two at 20v. I have ordered a much larger heatsink so that should help.

I was able to get a fluorescent bulb to flicker when placed right next to the secondary :), which shows the coil is slightly working. No sparks off of the breakout point though.

Let me know what you guys think.

Get rid of the DSO138 and find a cheap/for free old 20 MHz analog oscilloscope instead, it will do you much better :)

I agree with the others, you are running at a too low input voltage to expect to see any real working circuit, your antenna could also go up to half the height of the secondary coil, then retract it if there is sparks forming on its tip, a little corona is normal, but not sparks .

If you have a flickering fluorescent bulb, you are good to go, I assume you are using a variac, so get up to at-least 100V input.

8
The RRU3928 is an outdoor remote radio unit. It processes baseband and RF signal data. With the Software Defined Radio (SDR)technology, the RRU3928 supports the dual-mode operation of any two modes of GSM, UMTS, and LTE through software configuration modification. RRU3928 has a dual-transmitter and dual-receiver structure, which supports higher output power and carrier capacity.

It can f.ex. do 6x GSM carriers at each 10 Watt and 1x LTE carrier at 2x10 Watt or 4x GSM carrier at each 10 Watt and 2x UMTS carriers at 2x20 Watt.

This is the initial teardown and later on I will release part 2 which is the circuit analysis video.


9
Hi All,

I have managed to modify this cooker to external control, I have made this document to explain how.

I hope you can use it , and give inspiration to other projects. My purpose was to make a temperature controlled cooker for beer brewing.

* Patching IKEA TILREDA for auto control_ver1.pdf

Regards Carsten Dahl Hjarup

Good to hear from you Carsten and thanks for sharing your results. Which power level does it run at when fed with 20 kHz and which duty cycle did you use in your own oscillator?

I will soon get my unit back on the bench and dig a little deeper on the control IC, hopefully I can find a way to interface it by looking at the communication between HMI and control IC. It would be fun to get bumpless control over it instead of on/off control.

What is your conclusion on the pan detection function? is it really something it measures on some kind of back-emf on the driver output? Or it is just not a problem for you size you always have a pan on it?

10
Solid state Tesla coils / Re: First SSTC build, need help troubleshooting
« on: December 02, 2018, 09:57:04 AM »
Hi jesjes and welcome to HVF

Fumeaux said all the right things, first and foremost we need more information to help you :)

A very good first troubleshooting step is looking at the waveform: http://www.richieburnett.co.uk/temp/gdt/gdt2.html

Your DSO138 might not have the sample rate/bandwidth needed to measure these waveforms true to their real form, please check with a real oscilloscope if possible.

Some of the toroid cores you showed looks like iron powder cores, did you get some high permability material cores with AL above 5000? The Hirel I assume would be in a working region for this.

11
X-ray / Re: My X-Ray Machine
« on: November 28, 2018, 07:14:52 PM »
Hi neukyhm and welcome to HVF :)

That is a nice little machine you built, you really went all in on the details in the construction, which leads me to say that its a wonderful build process video. I like the body cam / CAD overlay combination.

Now for the questions :)

What body cam are you using?

What kind of intensifying screen is it that you are using? I have on/off been looking for phosphorus casettes for future project, but never found any reasonable priced.

What kind of control do you have between the Arduino UNO and the ZVS HV supply? Is it just on/off control of the supply voltage or did you extend the ZVS driver with more active driver circuitry?

12
It is not a matter of EMI that rules out the smaller micro controllers form being used in a driver.

It is clock speed and processing power as the analog OP-amp / digital 74xx functionality is moved from hardware to software domain.

Calculation of phase lead instead of using a inductor is a example of this. Or integration of a PFC stage in the same controller is another.

Be sure to calculate if your analog input is fast enough, enough samples, response time etc. to match a 74xx IC that it replaces.


13
Solid state Tesla coils / Re: My First SSTC
« on: November 27, 2018, 08:53:35 AM »
Neat little coil with a good range of hacks and shortcuts to make it run, but nevertheless, getting sparks from your first coil is all that really matters. It is a jump pad into building something bigger and better once you get the craving for longer sparks :)

If you still struggle with finding a easy PCB cad tool, I have used https://www.expresspcb.com/ for many years, its simple and there is no complex libraries, settings etc. but also there is no gerber files, but if you only do toner transfer it is perfect for that. Else check out the recommandations in this thread for other programs: https://highvoltageforum.net/index.php?topic=354.0

14
Dual Resonant Solid State Tesla coils / Re: My First DRSSTC
« on: November 23, 2018, 06:39:47 AM »
All those waveforms look good, however it is a bit overdamped once you connect the IGBT gates. Try to use a lower value gate resistor.

See this for future troubleshooting:  http://www.richieburnett.co.uk/temp/gdt/gdt2.html

Sent from phone.

15
/>
Circuit analysis of a Nokia Siemens Networks Flexi BTS base station. This have been in service as a 6 antenna GSM system for mobile telecommunications.

GSM/EDGE, WCDMA/HSPA and LTE capable. 2x40 Watt output power.

If you missed part 1, see it here: http://kaizerpowerelectronics.dk/teardown/nokia-siemens-flexi-bts-base-station-teardown-power-amplifier-part-1-of-2/



Above picture shows the coaxial cavity band pass filter which in popular speech is called a duplexer or diplexer. For a explanation on how this works, watch the first part of the video shown here above.



The duplexer control board and front end is managed by a ARM7 TDMI microcontroller with part number TMS470R1A288PGET. It is a 32-bit 24 MHz RISC processor.

Anaren Xinger II XC1900E hybrid couplers are used for phase split before feeding into the low noise amplifiers for signal transfer from duplexer module to power amplifier module.



The last picture could possibly show the DAC used for the transmit chain. It is a TI DAC56721 which is a 14-bit DAC capable of 275 MSPS.

The power amplifier consists of a series of low noise amplifiers, general purpose amplifiers and power amplifiers. The first few amplifier ICs are not able to be identified as their part numbers are not unique.

First identifiable IC is a Freescale M005N 0.8-2.2 GHz 18.5 dB general purpose amplifier that feeds the Freescale SW7IC18100N which is a power amplifier rated for 100 Watt dissipate at 1.8 GHz.

Two output circulators is used for double protection against reflected energy from the duplexer and antenna array.



The system board main processor is a unknown TI FPGA that has a generic Nokia Siemens part number which is not identifiable. It has a Marvell Alaska 88E1111 Gigabit network controller to handle the optical network interfaces.

A Texas Instruments TI DSP IC could be used for the first stage digital to analog conversion, purely guessed on from its location on the PCB. It is the TMS320TCI100 (C64x series) with is running at 720 MHz and is able of running 5760 MIPS.



The analog to digital signal path starts with a ceramic resonator band pass filter (explained here:
) which feed into a Maxim MAX19995 dual 1.7-2.2 GHz downconversion mixer (explained here:
) which by the use of a local oscillator can bring down the carrier frequency of the signal to something lower that is easier to work with.

The two separate lines now go through the ultra low loss 21 MHz band pass filters from Epcos. The B5221 is a 172.8 MHz SAW IF filter (explained here:
) before being fed into either a ADC or another mixer, the ST PARIS part is not identifiable.

The last stage is the Analog Devices AD9218 which is a dual 10-bit analog to digital conversion IC capable of 105 MSPS.

16
Vacuum tube Tesla coils / Re: Usable vacuum tube?
« on: November 22, 2018, 11:36:49 AM »
It all comes down to the class of transformer that you are willing to invest in, so its all a design option what kind of physical size or temperature rise you will allow.

If you really need to make a small transformer, you are forced to design it for a higher temperature and thus you need to use materials from a higher insulation class, making it more expensive, but space was your priority. The other way around you can as seen with MOTs dont care about size and you can manufacturer it cheaper.

See more here: https://en.wikipedia.org/wiki/Insulation_system

17
Hi everybody!

I am 17 years old, and have taken an interest in the electronics hobby since I was about 6. I am from Australia, and have just completed year 11. I have previously built a small SSTC, and am now working on my first DRSSTC. I've joined the forum primarily to seek advice on the DRSSTC (not going quite to plan at this stage...  :P), but I also hope to stay around, and help others.   :)

I look forward to getting to know you all.

- sjsimmo

Welcome to HVF :)

We will soon get you going with that DRSSTC and please do make a thread about your SSTC if you want to show it off, looks like its built on top of a PC power supply?

18
Dual Resonant Solid State Tesla coils / Re: My First DRSSTC
« on: November 20, 2018, 08:32:47 PM »
I agree with Laci on the full bridge rectifier on the OCD, you need some fast small signal diodes here.

The UCC drivers should be good enough to drive a full bridge of TO-247 IGBTs, so as long as the GDT is made properly that should work ok.

There is a only a few things can make UCCs explode that way. Driving them into a short circuit or maybe a saturated GDT? If there is no load connected to its output, they can oscillate into MHz region from their own output capacitance and burn down.

Steve Ward has written on his site that all his early designs are not to be used as they are full of flaws and bugs. They are only there to keep a track of history. You should at least use the UD1.3b or UD2.1 if you are driving bricks. I never tried building his earlier designs, so I got nothing to add with experience on those.

19
Dual Resonant Solid State Tesla coils / Re: (DR)SSTC II
« on: November 20, 2018, 05:44:25 PM »
What about the static load test?Since the first snow arrived today,I'd like to make tests inside,without the counterpoise. :)
Is there any RMS current formula for a DRSSTC,just to make sure that it will not blow any fuses?!

Try the RMS current calculation I did here, just with some more "real" numbers, as this example is used to design the DC bus capacitors needed, its set with very high figures: http://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/dc-bus-capacitor/

20
Could you please format your "table" of data so its more what numbers are for what. It seems you have 3 coil data vertical, but measurements horizontal?

I tried 920 turns, 1.77" radius and 6.63" long of awg34 and got 425 kHz in JavaTC, so im wondering how you wrote that table

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