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Flyback Arc Contest

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LAN_403

lpfthings

Tue Mar 25 2008, 05:33AM

Registered Member #1361 Joined: Thu Feb 28 2008, 10:57AM
Location: Cairns, Australia
Posts: 305

I have a few vids of my old flyback on youtube. The arc isnt very high current, but the voltage is pretty high. When i connect the internal cap (this is JUST a HV cap, NOT a voltage multiplier) The output power increases dramatically, but only for a short burst of power.

and

Marko

Wed Mar 26 2008, 02:58PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145

Hi guys,

I'm genuinely puzzled how some of you can make flybacks stand such enormous open-circuit voltages for prolonged time without blowing up, especially some of Jan's flybacks seem to be really indestructible.

Jan, do you now have your flybacks in oil? Arcs starting at 10cm looks like it would pretty surely track over surface of most flybacks.

What is the max of real power throughput you guys could repeatedly achieve?

Most I could stretch out of an DC flyback was some 11cm or so, starting at about 3 cm.
I used a mosfet halfbridge directly which is not a best option but works for low power levels.

One of problems with DC flybacks is that it is hard to get your own primary wound(especially if it has lots of turns), core is not neat as with old style transformers.
At first I used enameled wire wound on free core leg (around the steel clamp!) and it worked pretty well, until the insulation damaged and it blew up.

Back then I was an idiot and believed that I could use flyback's internal primary and get the required leakage inductance using a bigger airgap.. which resulted in massive magnetizing current, heating and ruined transformer.
All due to impatience for running a lifter (which only flew up for few seconds), while I could have built a proper flyback converter.

Some AC flybacks I had were probably dead already, they started arcing over even at low power level. Only have 2 really small ones working, and 2 DC flybacks with capacitors (can draw arcs only with a huge high voltage resistor on output).
So I'm pretty much out of this story, not in primary school anymore and hard to find junk over here.

There's nothing organized here and to actually find flybacks or MOT's I would have to dig garbage (I mean, 'ordinary' garbage.)

Nice to see this thread back up, makes me nostalgic... I miss the atmosphere of the old forum, it's completely different since then...

Marko

Dr. Dark Current

Wed Mar 26 2008, 04:24PM

Registered Member #152 Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384

Marko wrote ...

Hi guys,

I'm genuinely puzzled how some of you can make flybacks stand such enormous open-circuit voltages for prolonged time without blowing up, especially some of Jan's flybacks seem to be really indestructible.

Jan, do you now have your flybacks in oil? Arcs starting at 10cm looks like it would pretty surely track over surface of most flybacks.

No i have no flybacks in oil, I don't know but most of the dc flybacks seem to destruct, well above 60-80KV. The ac ones destroy at ~30KV usually but the white one in my prev. post is an extra tough guy, I think it was generating ~50KV and there was huge ac corona from the output.

Marko wrote ...

What is the max of real power throughput you guys could repeatedly achieve?

Seems to be ~400-500W if I want to run them for a while, and they usually take 600-700W for short (<20s) times. But then again I've destroyed just one dc flyback and I've did bad things to the other ones and they are still alive.

Marko wrote ...

Nice to see this thread back up, makes me nostalgic... I miss the atmosphere of the old forum, it's completely different since then...

hmm yes, the first purple squealing arcs I've achieved from an old dusty ac flyback with the single transistor driver, were amazing, and the big white ones for some reason are not so amazing... Exciting maybe but not amazing.

J.M.

Zum Beispiel

Wed Mar 26 2008, 04:42PM

Registered Member #514 Joined: Sun Feb 11 2007, 12:27AM
Location: Somewhere in Pirkanmaa, Finland
Posts: 295

Plasmaddict wrote ...

hmm yes, the first purple squealing arcs I've achieved from an old dusty ac flyback with the single transistor driver, were amating, and the big white ones for some reason are not so amazing... Exciting maybe but not amazing.

I know what you mean. I remember when I made that single transistor flyback thingy and was so amazed. "Woah, that must be like, 10000 volts"

Last summer I build my Mark II SSTC and got bored of it in a week, though I still drag it out every now and then.

I think HV is just like any other addiction: you need larger and larger doses of it to get the same buzz

uzzors2k

Wed Mar 26 2008, 07:07PM

Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308

Marko wrote ...

Nice to see this thread back up, makes me nostalgic... I miss the atmosphere of the old forum, it's completely different since then...

Then you should have been on the older forum, just going to the old page brings me back. I miss those colors...

*Sighs*

I remember my first 555 driver, it was so awesome! Puny 5 -15 mm sparks. And it felt like such a reward for piles of hard work. I remember nearly asking about where to put each wire, on such a simple circuit! It's a wonder I wasn't banned.

Dr. SSTC

Sun Jun 22 2008, 01:29PM

Registered Member #1407 Joined: Fri Mar 21 2008, 07:09AM
Location:
Posts: 222

i remember when i was 10 i got a step down transformer and rapidly conected and disconected a 12 volt lead acid batery from the primary side i thought those lithe sparks were amazing

quicksilver

Sun Jun 22 2008, 03:22PM

Registered Member #1408 Joined: Fri Mar 21 2008, 03:49PM
Location: Oracle, AZ
Posts: 679

[quote]
I know what you mean. I remember when I made that single transistor flyback thingy and was so amazed.
[quote]

I'm at that stage right now. I'm just starting to explore the fundamental steps that those simple circuits are all about. The work & time I put into theses little things is quite out of balance with the actual product, but that isn't really the excitement. The learning is so incredible!

The actual length of the arc really CAN be pushed a tiny bit by bit by some of the most incremental adjustment.....But the REASONS why they happen are so marvelous. There are so many ways to approach just this subject alone. If the concept were to have narrowing parameters such as the longest arc with 12v or the longest arc with a particular circuit, then the narrowing would focus the study agenda. But the broadening of this subject to simply the "longest arc with a LOPT" allows for experiments virtually without end!

In fact I'm just waiting until someone (with powerful engineering skills) looks deeper into the circuits and finds those issues that must have occurred to Mazilli because that man was thinking "outside the box" when he came up with his idea. And when that happens with one man; others soon allow their creativity to grow as well.

Antonio

Mon Jun 23 2008, 09:42PM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

The normal operation of a flyback transformer is, essentially:
When the driver transistor switches on, current flows trough the primary winding in a ramp waveform, storing energy in the magnetic field.
When the transistor switches off, the primary current is interrupted, and current flows trough the secondary winding and rectifier diodes, rising the output voltage to a few tens of kV. At the same time a quite high voltage appears over the driver transistor, easily more than 1000 V.
The maximum output voltage is limited by the voltage that the driver can sustain. Usually a capacitor and a diode are connected across it, to limit the voltage and recover unused energy.
Greater than normal output voltage can be obtained by winding another primary coil, with less turns than the normal one, but soon the output insulation will be insufficient.
Since energy is required to charge the capacitances on the primary and secondary sides, the current shall be interrupted when there is enough energy stored in the magnetic field. This energy depends on how long the ramp lasts and on the power supply voltage. Increasing either one has the same effect, so it is possible to obtain high voltage at the output with a low voltage power supply, if the transistor is kept on for more time. There is a limit due to the resistance of the primary coil, and a limit in the stored energy due to core saturation.
To obtain greater average current at the output, the power supply voltage must be increased. This allows faster repetition of the cycle, since the transistor must be on for less time.
Long arcs that start short but are "pulled" require a lot of current after the arc starts. The voltage is not high. It is maximum before the start of the arc.

Typical operating frequencies are a few kHz to several tens of kHz. More than this can easily lead to the driving transistor failing to interrupt the current, with a curious effect. When not enough time is left between successive pulses, the transistor conducts continuously during two or more cycles, and the current ramps up to two or more times the normal value. If this continues, something burns, but when the effect occurs for the first time, the output voltage goes up suddenly, giving the impression of a "resonance". With more current flowing the transistor switches off normally after two cycles. This is probably the "resonance" effect that is sometimes described.

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