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Registered Member #1025
Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566
Hi guys, Despite there are many threads dedicated to ignition coils on 4HV I think it is not a bad idea to spend some time with this topic again. Mainly because, among all the garbage you can find on the street the ignition coils are relatively common and by using a clever design they can serve as pretty powerful HV source. My latest circuit design is based on super-clever boost trap circuit introduced by Steve Conner with few modifications (I used tl494 instead of 555timer). I also made a trick how to power the iggy straight from mains but keeping the voltage on primary in values the coil can survive. I simply used 70uF rolled capacitor in series with bridge rectifier followed by 2.2 mF elyte-capacitor. Such simple current limiter trick basically substitutes high power transformer - it only needs to be plugged to the wall always after the gate drivers are already running.
At the moment the setup involves two anti-parallel ignition coils (giving above 50KV), two IRF460A FETs in half bridge running at 3KHz. Power consumption is almost 400W
I plan to make some serious measurements and long run tests and try to keep you updated. I also plan to finish a HV bridge rectifier and plug this system into my SGTC – that should be really something.
I will also send complete schematics for potential followers...
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Mates wrote ... Despite there are many threads dedicated to ignition coils on 4HV I think it is not a bad idea to spend some time with this topic again. Mainly because, among all the garbage you can find on the street the ignition coils are relatively common and by using a clever design they can serve as pretty powerful HV source.
I couldn't agree more! There you've got quite a powerful Disruptive Discharge Transformer, much more solidly and reliably built that any TV or Monitor LOPT, and few folk seem to be able to think of anything to do with them except make showers of sparks, or see how far they can push them before the oil fails.
I wrote some time ago and in another thread of my meaurements of L, R, T, and fo of a few ignition coils I had to hand, to enable folk to better design circuits using them, but there seemed no general interest in the subject, so I stopped writing in about it.
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Are you sure about the 1000W? Isn't it VA? The series capacitor you mendioned surely adds a lot of reactive power. That arc look more likely around 200-300W.
But nice nonetheless
Harry, how much power do you think an ignition coil can output continuously? The old type AC TV transformers can do 200-300W of power into an arc continuously from my experience, and the non-audible operation is an advantage too, at least for my ears
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
Dr. Kilovolt wrote ...
Harry, how much power do you think an ignition coil can output continuously? The old type AC TV transformers can do 200-300W of power into an arc continuously from my experience, and the non-audible operation is an advantage too, at least for my ears
I don't have the kind of equipment needed to measure RF power in the tens of kilovolts range, but data sheet values for 12V ignition coils are between 60W and 80W of power input. The largest LOPT I could find iin the HR Diemen "bible" has an output of 27kV @ 2mA.
I have three large, unused, old American LOPTS and have just got them out to look at them. It isn' easy t to understand how such dense windings of such fine wire could be rated at 300W
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Obviously, ignition coils are higher voltage than NSTs. Though that being the truth, the secondary windings are as thick, if not thicker than a 60ma NST secondary! I can actually wind the ignition coil secondary wire around my hand, while the NST normally broke. It is not much thicker, maybe 2AWG difference. I would say the ignition coil secondary is 36 gauge. The NST may have been the same thickness, but i guarantee it was not bigger! The easily broken NST wire can be attributed to how old it was, though, the ignition coil was very old as well.
Though the core will saturate easier, especially since you have to find the frequency best suited for your needs. Also, heating is a much bigger problem, and the primary is wayyyy too thin to push the kind of current the secondary would withstand. I am sure with your ignition coils running 1kw (not reactive, i mean real average) in anti parallel without over voltage, it would last. Minus primary failures. That stuff is 24 gauge! Rather, mine was, it may vary from coil to coil. Probably not an industry standard. There is well over 100ft of it in my 'normal' run of the mill iggy.
Cool stuff, keep it up. I consider you the master of ignition coils, and Jan the master of flybacks .
Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
Harry wrote ...
I don't have the kind of equipment needed to measure RF power in the tens of kilovolts range, but data sheet values for 12V ignition coils are between 60W and 80W of power input. The largest LOPT I could find iin the HR Diemen "bible" has an output of 27kV @ 2mA.
Well, that would be if you drive it in flyback mode, but in bipolar forward (a bridge) it can do MUCH more.
Some time ago I built a demonstration Jacob's ladder, which used a classic "flyback" core, with two secondaries stuck on it on each "leg". The input power peak (with the longest arc, around 6") was ca. 500W, which means over 1000VA on the transformer, and it ran continuously for 6 hours. Surely got very hot, but survived.
Registered Member #1225
Joined: Sat Jan 12 2008, 01:24AM
Location: Beaumont, Texas, USA
Posts: 2253
Dr. Kilovolt wrote ...
Harry wrote ...
I don't have the kind of equipment needed to measure RF power in the tens of kilovolts range, but data sheet values for 12V ignition coils are between 60W and 80W of power input. The largest LOPT I could find iin the HR Diemen "bible" has an output of 27kV @ 2mA.
Well, that would be if you drive it in flyback mode, but in bipolar forward (a bridge) it can do MUCH more.
Some time ago I built a demonstration Jacob's ladder, which used a classic "flyback" core, with two secondaries stuck on it on each "leg". The input power peak (with the longest arc, around 6") was ca. 500W, which means over 1000VA on the transformer, and it ran continuously for 6 hours. Surely got very hot, but survived.
Six hours at 500 watts? .
I have pushed a DC flyback to 1.4kw for very short time, using a fullbridge at 80 volts. Unfortunately, the frequency was 30khz which would produce too much voltage, so i could not draw the arc out too much. After some 20 seconds it was hot, after 40 it was uncomfortably hot! In the second clip with 80 volts the arc was loud! The frequency was well above audible range.
Registered Member #1025
Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566
Dr. Kilovolt wrote ...
Are you sure about the 1000W? Isn't it VA? The series capacitor you mendioned surely adds a lot of reactive power. That arc look more likely around 200-300W.
I have to apologize – you are of course right - the real power consumption (measured on the power-meter) is close to 400W
I’ve been playing with the two coil system a bit. I made a simple Jacob’s ladder and let it run for 10minutes. The coils were warm but not seriously, the driver stayed almost RT. My next plan is to raise the power up. I’ll keep you updated...
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Pushing the balls of ignition coils
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