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Spiral impulse generator = rolled cap Blumlein induction coil!

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LAN_403

Tesladownunder

Sat Apr 19 2008, 10:09AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

This is an odd little high voltage generator which is in principle, part Blumlein generator (like the nitrogen laser uses) and part induction coil. It is very simple and compact and very easy to make. They have two copper strips insulated from each other and rolled up like a rolled capacitor. Apply a few kV at one end of both strips and they will charge up. Short circuit one end with a spark gap and a very fast pulse passes in the Blumlein capacitor strips. This will have a magnetic effect as the current in each copper strip (my brain starts to hurt here) will have an additive effect and like current in a coil will result in magnetic induction in the remaining turns of copper strip.

The first photo shows the spiral impulse generator generating a 5 mm spark (perhaps 5 kV) from a 1 mm spark gap. The spark gap is between the two electrodes (which are not connected to each other) and the right upper electrode is the one that continues through to the output electrode strip with the longer spark coming off it. The capacitance between the two strips is 900 pF.

The second photo shows the 1984 patent that this comes from.
The next photo shows the strips of copper foil of 10 x 62 mm. I have soldered two together for the long winding. Hence there are two parallel strips of 4.5 turns and one strip only continues on for another 4.5 turns.
The last photo shows the start of the copper strip windings separated by polyethylene sheet.
It doesn't seem too efficient but I don't really understand the setup enough to know which way to modify it best. I imagine that I could make one with more turns to start.

TDU

1208599162 10 FT0 Hvspirallineimpulsepatent

Proud Mary

Sat Apr 19 2008, 01:17PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

How intriguing!

I have found another patent, which discusses the problems of increasing the power output of the basic spiral, in order to put forward a method of its own for reaching into the megavolt range from a 10kV supply:

Multi winding spiral generator United States Patent 5567995

uzzors2k

Sat Apr 19 2008, 05:43PM

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

It seems like these can have large multiplication ratios. The one here has a step up ratio of 16 at 9kV! A simple alternative to Marx generators maybe, if we can figure out how to make them that efficient.

Spedy

Sat Apr 19 2008, 07:09PM

Registered Member #964 Joined: Wed Aug 22 2007, 12:39AM
Location: Stockton, CA
Posts: 134

Wait a sec, I'm confused here.

so, you short circuit it and it makes a bigger spark where you short circuit it? I don;t get it...
Oh wait, Is it like this?

Proud Mary

Sat Apr 19 2008, 09:05PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

I have found an explanation of the operation of the spiral line here:

Dr. Shark

Sat Apr 19 2008, 09:56PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

Wow, what an amazing concept. I went right ahead and tried to make one

but I could not get it to work yet. Maybe it is a little small, is is constructed from a single rolled up overhead sheet so the "secondary" (is it still called that in electrodynamics?) is only 70cm long or so, which is about a third of what Peter has.
I'll keep playing with it though, especially the thread linked to by Uzzors makes it seem really worthwhile. I'll have to be able to puncture that OHP sheet!

EDIT: Well, I sort of got it to work by cutting down on the extra insulation material (pun intended). Still the output spark is rather puny, about the same as a piezo lighter.

I don't think there is anything magical or electrodynamical about this circuit as I build it, at least I can explain without the electric field vectors, traveling waves, reflections and all that. After all it IS just a Tesla coil with tank capacitor and the primary scrambled up. So it does not take the slightest bit of waves propagating at the speed of light to get a spark at the output.
I am pretty sure the "real" BlÃ¼mlein pulseforming lines, which are used for creating nanosecond pulses, take a lot more work that just rolling up a piece of tinfoil. Have a look here

for some BlÃ¼mlein bashing, although that may just be a minority opinion.

Proud Mary

Sat Apr 19 2008, 11:45PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Dr. Shark wrote ...

I am pretty sure the "real" BlÃ¼mlein pulseforming lines, which are used for creating nanosecond pulses, take a lot more work that just rolling up a piece of tinfoil. Have a look here

for some BlÃ¼mlein bashing, although that may just be a minority opinion.

N2 lasers need nanosecond pumping, which makes a practical Blumlein difficult to implement, but more usual Blumlein configurations in the microsecond pulse range are not at all difficult to construct, and drive with a rotary spark gap, as this paper shows:

You just need to have the money to buy RG213 coaxial cable!

jpsmith123

Sat Apr 19 2008, 11:45PM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843

Somewhere I have a few pdf papers on these things. If anyone is interested maybe I can try to find them and upload them somewhere.

The one paper I don't have is the one referenced in the following linked paper, which apparently discusses the detailed design.

(Wrt blumlein pulse generators it seems that the limiting factor for short, fast pulses is the switch...for fast di/dt you need high electric field across the spark gap which generally means pressurized gas or a liquid dielectric. BTW here's an interesting paper on a fast blumlein pulser

Tesladownunder

Sun Apr 20 2008, 02:57AM

Registered Member #10 Joined: Thu Feb 02 2006, 09:45AM
Location: Bunbury, Australia
Posts: 1424

Here are a couple of diagrams to clarify the setup.
There is no connection between the two HV electrodes. It does not resemble a TC at all (although something similar might be feasible but that is another project).
There is a standard two parallel electrode strips rolled up like a home made rolled cap. The extended one just allows more voltage step up.
Actually, I don't know how much induction there really is and how much is just transmission line coupling.

BTW for all those who wondered why their rolled caps failed at the ends, this is why. A few weeks ago, I autopsied 2 of my old big rolled caps to dispose of the oil and the failure was at the ends away from the electrode attachment, ie where the HV is picked up.

1208660215 10 FT43795 Hvspirallinediagram

1208660215 10 FT43795 Hvspirallineextendeddiagram

Mates

Sun Apr 20 2008, 07:27AM

Registered Member #1025 Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566

I have few ideas regarding this thread...

What about to try coax cable istead of the rolled-insutated stripes...Would it work?

And it would be interesting to try solidstate based "spark gap" because as understand this concept it has no real frequency limit (maybe such device could be used for plasma speakers ???)

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