Strange effect from HV discharge

[johnb003]

I was getting ready to perform some experiments with HV to try to build something like a gray tube or at least I wanted to study the effect if possible, but before I even got to doing any of the experiments, just testing my power supply I observed something totally unexpected.

My HV power supply is just a car battery, 555 timer, and a flyback transformer. So I connected everything up and to make sure everything was working I wanted to just check the air gap discharge from the flyback transformer. So I held the negative terminal of the secondary where it was insulated in my fingers, and brought the exposed part of the wire close to the hv terminal. I didn't have my fingers anywhere near the HV terminal and the wire was well insulated, but as the discharge happened I noticed a fairly strong vibration in my fingers where I was holding the wire.

By the way, a flyback transformer internally has diodes at every layer of the windings, so each diode doesn't have to withstand high voltages, and as a result the output is uni-directional. That's why I figured the negative side would be relatively safe.

I could just hover my fingers very close to the wire and I could feel the vibrations just as strongly in the air. It felt like I had been holding a magnet over a coil that was oscillating. I can't be certain that the force wasn't in fact electrical, but it was not shocking, it was just tingly, like holding an electric toothbrush, or something.

I don't understand, why would this happen on the negative terminal? Why could I feel this so clearly even through the insulation?

I just tried replacing a segment of the negative terminal with about 8 inches of 1/2 inch aluminum round rod. I was too afraid to touch the exposed surface to see if I could feel the effect, so I put a few layers of clear packing tape, which I've learned is a pretty good insulator. I could still feel the effect in the area surrounding the rod, while I was discharging into the rod.

I'm going to try to learn more...

Any ideas?

[lighty]

Capacitive coupling.

[Inquorate]

Does it depress the surface of oil?

See what I wrote on bodkin's thread, physics of the primary state, page 4.

[lighty]

@Inquorate

There is no need to complicate things. johnb003 held HV secondary. He was capacitively coupled with conductor and with ground. All the insulation in the world won't prevent that. And yes, what he felt was a simple very low current stimulation of his nerves. If he was to raise or lower the frequency the feeling of "toothbrush vibration" would change. It's as simple as that.

[Inquorate]

Chastened

@ lighty, point taken, the way I read it, the vibration was felt in the air, my mistake.

[johnb003]

@Inquorate

There is no need to complicate things. johnb003 held HV secondary. He was capacitively coupled with conductor and with ground. All the insulation in the world won't prevent that. And yes, what he felt was a simple very low current stimulation of his nerves. If he was to raise or lower the frequency the feeling of "toothbrush vibration" would change. It's as simple as that.

Actually I was holding the ground. I was moving the ground wire close to the hv terminal.

I originally tried the test with the negative terminal of the secondary (not the HV terminal), I know the transformer is oscillating so you could try to say either terminal can be HV, but in the flyback, there are diodes internally so it's only hv on the one terminal (the one I wasn't holding).

Since the original post I've done more tests. I connected secondary ground with the primary ground, and still I felt the effect.

You may be completely right about the capacitive couple, I just didn't expect it from the ground wire. I'm not trying to claim anything really, I just wanted to understand what was happening.

Also I thought a good way to test the capacitive coupling, would be to put some metal around the metal rod and see if I can get a voltage. I tried it, I used a 25' roll x 6" wide, grid (grid spacing is about 1/8 inch) it's a metal screen / mesh thing of galvanized steel. The inner diameter is about 4 inches. So the grid is surrounding the rod, separated by about 2 inches, and from this I get some small sparks back to the rod.

`John

[wpage]

Sounds interesting

Very interesting...

Any images of the arcing?

[lighty]

I originally tried the test with the negative terminal of the secondary (not the HV terminal), I know the transformer is oscillating so you could try to say either terminal can be HV, but in the flyback, there are diodes internally so it's only hv on the one terminal (the one I wasn't holding).

Diodes have nothing to do with the HV voltage on the secondary. They will regulate current flow polarity but both endings of secondary are producing HV. Simply put, when you put diodes on one end of secondary it doesn't mean the other end of secondary is dead.

I connected secondary ground with the primary ground, and still I felt the effect.

I think I know what's bothering you. You're using inaccurate terminology. The wires you speak about are not Earth ground wires. One could rather call them Common potential wires. However Common wires still have floating potential in relation to Earth ground. In other words you have voltage between your Common and Earth (on which you stand and to which you're capacitively coupled).


[quote] I tried it, I used a 25' roll x 6" wide, grid (grid spacing is about 1/8 inch) it's a metal screen / mesh thing of galvanized steel. The inner diameter is about 4 inches. So the grid is surrounding the rod, separated by about 2 inches, and from this I get some small sparks back to the rod.[/qutoe]

Of course you're getting sparks. HV charge likes to jump to any body of sufficient self-capacitance. It doesn't really matter if we're talking about Earth or some metallic body. Try to imagine it in a very simplified way- conductors sitting on a HV potential would like nothing better then to get rid of some of the charge. So it seeks any conductive body in vicinity. Then it will relase some of it charge either through spark (current) or through capacitive coupling (E-field).


Sorry to say this mate, but this is a common effect when dealing with HV. What's bothering people is the fact that there is a heavy insulation around HV wires. They don't realise that insulation won't prevent capacitive coupling and transfer of energy. Only the lowering of mutual capacitance between HV conductor and other conductive body will lower energy flow between them. One of the reasons why so called "Avramenko plug" won't work over great distances without significant losses is capacitive coupling of various components of the system with Earth ground. There are methods of reducing those losses and raising efficiency but that is out of the scope of this particular discussion.

[lighty]

I originally tried the test with the negative terminal of the secondary (not the HV terminal), I know the transformer is oscillating so you could try to say either terminal can be HV, but in the flyback, there are diodes internally so it's only hv on the one terminal (the one I wasn't holding).

Diodes have nothing to do with the HV voltage on the secondary. They will regulate current flow polarity but both endings of secondary are producing HV. Simply put, when you put diodes on one end of secondary it doesn't mean the other end of secondary is dead.

I connected secondary ground with the primary ground, and still I felt the effect.

I think I know what's bothering you. You're using inaccurate terminology. The wires you speak about are not Earth ground wires. One could rather call them Common potential wires. However Common wires still have floating potential in relation to Earth ground. In other words you have voltage between your Common and Earth (on which you stand and to which you're capacitively coupled).

I tried it, I used a 25' roll x 6" wide, grid (grid spacing is about 1/8 inch) it's a metal screen / mesh thing of galvanized steel. The inner diameter is about 4 inches. So the grid is surrounding the rod, separated by about 2 inches, and from this I get some small sparks back to the rod.

Of course you're getting sparks. HV charge likes to jump to any body of sufficient self-capacitance. It doesn't really matter if we're talking about Earth or some metallic body. Try to imagine it in a very simplified way- conductors sitting on a HV potential would like nothing better then to get rid of some of the charge. So it seeks any conductive body in vicinity. Then it will relase some of it charge either through spark (current) or through capacitive coupling (E-field).


Sorry to say this mate, but this is a common effect when dealing with HV. What's bothering people is the fact that there is a heavy insulation around HV wires. They don't realise that insulation won't prevent capacitive coupling and transfer of energy. Only the lowering of mutual capacitance between HV conductor and other conductive body will lower energy flow between them. One of the reasons why so called "Avramenko plug" won't work over great distances without significant losses is capacitive coupling of various components of the system with Earth ground. There are methods of reducing those losses and raising efficiency but that is out of the scope of this particular discussion.