Re: Exploding wires - duelling machines
ragnar, Sun May 21 2006, 10:55AM

But Peter... it's not April fools' day..

Re: Exploding wires - duelling machines
Tesladownunder, Sun May 21 2006, 11:14AM

Ummm.. Does that mean you don't believe this is a bona fide shot or just the reference to the game? I may be devious at times but I don't have Photoshop.

Another shot from a different angle with the same power, hoping to characterise the plasma around the transformer. You can see the flash around the transformer particularly going upwards. I don't think that it is a flashover across the inductor on this shot.
My suspicion is that it is the plasma channel being forced in one direction parallel to the axis of the coil due to the whatever-hand rule as the current in the channel is coming out at right angles. As the voltage reversal occurs the flash heads in the opposite direction.
What is also interesting is the vibrations in the string caught in the blue flash. There are harmonics as well since it is not a clear sine wave. (My version of "string theory").

Peter

Re: Exploding wires - duelling machines
Marko, Sun May 21 2006, 11:24AM

Don't you fear of ruining the transformer that way?

Re: Exploding wires - duelling machines
Tesladownunder, Sun May 21 2006, 11:42AM

The transformer winding is very solid and epoxy encased for the 3kv AC which is about 5kV peak which is what I am putting into it as DC.
I'm not scared. It has just been a boat anchor until now.
If I have voltage issues I have other higher voltage transformers.

The reason I got onto this today was a failed attempt to pull out long arcs by pushing 5kV through the coil then physically breaking the circuit with a spring loaded make and break switch. It was really dissappointing and I expect there is a clear optimum of make to build up the current in the transformer to a peak then rate of break to allow the energy in the coil to maintain the voltage and current to draw the arc. I was getting voltage reversal on my meter so was probably holding the make too long. I didn't really take any photos of the setup as I was hoping for good results around dusk when lighting is optimal for these type of things.
Mind you the transformer will only store 200J of magnetic energy (10KVA divided by 50Hz).

Pic is a very old one with my pulling an arc off it when it is ballasted using apalling safety procedures.

Peter

Re: Exploding wires - duelling machines
Marko, Sun May 21 2006, 12:20PM

Damn, I would like to have a such core at least!

Probably not fun to you after having all theese beasts...

Re: Exploding wires - duelling machines
Steve Conner, Sun May 21 2006, 03:55PM

Transformers store hardly any magnetic energy, because the core doesn't have an airgap. I doubt it stores anywhere near 200J. If it did, it would draw 10kVA worth of magnetizing current when connected to the supply but unloaded.

Re: Exploding wires - duelling machines
Hazmatt_(The Underdog), Sun May 21 2006, 06:38PM

I know that picture is old and all, and ballasted...well okay maybe that would save your life, but what I wanted to say is this: Just because you have a ground wire on one side of the transformer don't think that tells the transformer its at 0V! because its not. This is a really bad practice for those new guys out there who are going to think that it works that way and could get killed by the HV on the lead.

Pictures like this worry me to no end.

Re: Exploding wires - duelling machines
Marko, Sun May 21 2006, 06:59PM

I couldn't recognize the connections from the pic, and I don't know if you could.

Secondary could be one side grounded, centertapped or not grounded at all.

If the wire he's holding in hand is really internally connected to ground he could blow up only by touching another electrode.

If it's center-tapped and apalling safety procedure conducts he again blows up.

If secondary is hanging he will probably get just a relatively minor displacement current shock,
probably not fatal and dependent on capacitance between secondary and earth.

Re: Exploding wires - duelling machines
Dr. Dark Current, Sun May 21 2006, 07:56PM

sorry but this just made me laugh


I dont see how Matt's post makes sense.. from the picture it is apparent that he's holding an insulated "stick"

J.M.

Re: Exploding wires - duelling machines
Hazmatt_(The Underdog), Sun May 21 2006, 10:29PM

It has little to do with holding an insulator. You could have an accidental brush by with the wire which there is only 600V rated!!!!!

I see X1 and X2 no 0, which means no gnd.

Its just dangerous all around.

Re: Exploding wires - duelling machines
Electroholic, Mon May 22 2006, 12:07AM

actually x1, x2, x3 and x4 are all L.V. windings.
then there is H1, H2 and 1-4 on the HV side.
but yea, theres no ground.

Re: Exploding wires - duelling machines
Tesladownunder, Mon May 22 2006, 12:48AM

Hey guys, give me a break. I was holding an insulated rod. The 3kv is floating with this amazing epoxy secondary. I was staying well away from any thing grounded. There would have been minimal coupling to earth anyway. Ballasting has nothing to do with safety. I was aware of all these things at the time. It's voltage is little different from a ballasted MOT with the difference that a MOT is grounded making it much more dangerous to touch one wire. Compared to adjusting a Nitrogen laser this pic is very safe.

Please remain on topic.

That's not how I understand it. When you turn on a perfect inductor you initially draw power to build the magnetic field. This effect is the thump that sometimes happens when you switch on a variac and is greatest at zero crossing (rather than switching on at peak voltage). After that net power is zero. In my transformer setup the current is far less than 10kVA when it is running at no load but energy had to be expended initially to build the field at turn on and this takes a few cycles until the voltage/current phase relationship settles. 10KVA (200J per 50Hz cycle) of power is what can be extracted from that field at close to maximum capacity. I would guess that it is a bit more as the 10KVA is the thermal limit as efficiency drops after that with increasing iron saturation losses.

The pic below shows the much brighter and very much louder exploding wire at the same energy without the inductor in the circuit.

Peter

Re: Exploding wires - duelling machines
ragnar, Mon May 22 2006, 03:51AM

I'm fascinated by your first picture, TDU... I'm trying to work out why the colour of the flash around your inductor isn't the same as the wire vaporisation flash.

What kind of shrapnel is left behind (if any) after a shot such as this?

Re: Exploding wires - duelling machines
Tesladownunder, Mon May 22 2006, 10:25AM

I am not sure about the different colour. As the plasma seems to extend around the transformer apparently in close proximity, it may mobilise some dust or sweat off the surface

I haven't seen any fragments, but 35G is very fine wire and 2.5kJ can let out a lot of smoke. My previous efforts with fine wire resulted in fragmentation and string of pearls appearance.

Pics of this and other wire thicknesses here

Peter

Re: Exploding wires - duelling machines
Richy, Mon May 22 2006, 01:51PM

Would it be possible to take a picture through a welding mask (or equivilent) to show more detail of the plasma? Or could this be done by reducing the exposure? It would be interesting to see what was going on around the inductor/transformer
Great pics nonetheless
Richy.

Re: Exploding wires - duelling machines
Tesladownunder, Mon May 22 2006, 04:24PM

I have taken photos of sparks through welding goggle filter(s) before in the pic below.
I could try this again. My camera has a lot of settings and is still using smarts like auto ISO which allows me to take 3 second exposures before the sun has set without overexposing. It will take some experimentation and fiddling with manual settings, I guess.
A heavily neutral filtered shot would be interesting to look at wire disintegration more closely.

Peter

Re: Exploding wires - duelling machines
Tesladownunder, Sun Jun 04 2006, 09:30PM

Finally found my iron wire. Here is how it goes on my cap bank. The return path is an aluminum tube. Shot was at 3kJ.

If anyone wants the hi res pic for wallpaper it is here.

Peter

Re: Exploding wires - duelling machines
Marko, Sun Jun 04 2006, 09:48PM

Wow, pretty scary!
Try not to set a fire wit this thing!

I wonder how long could you actually make a copper wire and still blow it up fully?

Re: Exploding wires - duelling machines
evilgecko, Mon Jun 05 2006, 12:21AM

Woah that is crazy you should get a video of the tesla. How do you switch it?

I just fired 182J of energy into a piece of solder and thought that was cool with all these little glowing balls of solder propelling themselves along the table. They hit small piles of black powder that happened to be spilt and made a woosh woosh sound.

Re: Exploding wires - duelling machines
Tesladownunder, Mon Jun 05 2006, 01:39AM

Switching is by a big heavily spring loaded switch activated by pulling a plastic spacer out with a very long string. Very crude but effective and reliable with minimal wear. I don't even think about the switch any more.

The video would be disappointing I think as the beauty of the picture is in the homogeneous trails seen in high resolution. It is all over in 1/2 second anyway. I have new video software but need to get up to speed with it. I have lots of room as I only have used 144M out of my 2 gig quota on Chris Russell's 1121.org server.

I am not sure how long a plasma channel I can get with very fine wire which is what I might try next.

Peter

Re: Exploding wires - duelling machines
evilgecko, Mon Jun 05 2006, 06:08AM

That beut I can't find any braided copper wire so I thought I might just make a mechanism that drops the wire I want to explode onto two points. I have 20x 450V 1800uF caps so 3.645kJ of energy might do something. But they are elctrolytics and on your web site you said they are slow? Is that because they are low voltage.

Re: Exploding wires - duelling machines
Tesladownunder, Mon Jun 05 2006, 08:53AM

Try an auto parts place or wreckers for braided battery cable.
The wire needs to be fixed securely or it will just spark at the ends so just dropping it won't work well and you will probably be too close.

Electolytics are slow so won't work for can crushing, but the energy still has to go somewhere.

Here is 1500 J of electrolytics and some aluminium foil.

Peter

Re: Exploding wires - duelling machines
evilgecko, Mon Jun 05 2006, 11:07AM

You have the right to show off

I tried dropping some solder onto two steel bars that were the electrodes of one 450V 1800uF and that worked well, it didn't just spark at the ends.

I don't feel the urge to crush cans unless I'm at the recycling centre it doesn't appeal to me. But exploding wire sure does. Next-to-do is to ramp up the bank to include all 20 and make some nice shiny iron electrodes (I know iron is a bad choice but I have plenty off it for no cost).

Re: Exploding wires - duelling machines
Fusion, Fri Aug 25 2006, 09:22AM

I calculated that a 0.5mm diameter and 5cm copper wire would be heated to 74000ºK ¿do you know if there where any reflected power?

Re: Exploding wires - duelling machines
Sulaiman, Fri Aug 25 2006, 10:20AM

Peter,
Nice photo's !

I suspect
1) The magnetic field generated by the transformer has little to do with the effect
because by design the flux is almost entirely within the core.
2) It's probably just Lenz's law at work
If you 'shield' the transformer with a metal plate (pass the wire through a hole)
I suspect you will get a similar result
even aluminium or copper etc. should 'spread' the arc due to
the magnetic field created by the current of the arc itself.

Just speculating.


Still nice photo's though!