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Impedance of a plasma arc

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Etesla:
I'm trying to design a plasma tweeter. I've made about 5 of them using various strategies over the last couple years but I'm really trying to optimize this one. I plan on winding my own transformer on top of a flyback core from an old CRT tv. I was going to drive the primary with a half bridge like a normal transformer, no flyback stuff. I believe the leakage inductance in the secondary will be the primary thing limiting the secondary current, which is what I think will be related to the intensity of the arc, and therefore the audible volume, of the final design. I think the way to get maximum power into my arc would be to match the impedance of the arc to the impedance of the secondary leakage inductance roughly.

However this leaves me with a challenge. I have no idea how to characterize the impedance of an arc created by flowing current through ionized air. I would imagine the things that matter most are the distance between my electrodes, and maybe the current flowing through the arc? Did anyone every do a study characterizing the impedance of ionized air? Does anyone have ballpark number, like a plasma about 2 inches long that looks 'pretty hot' with 2mA flowing through it is about 200 ohms?

I'll take any information I can get before I get antsy and run my own experiments...

radiolistener:
If I remember correctly, it will be close to resistance of a copper conductor at 20°C.

But it can vary depends on air chemistry, pressure and plasma temperature

coppercone2:
nonlinear at low currents. At high currents between say 50 amps it should be around 0.5 ohms for a 1mm length welding arc (taken from old book). And at 250 amps something like 90 miliohms. (the voltage drop stays constant) *

At lower currents say 10 amps it comes out to a few ohms . (say in this case I got about 3 ohms but its hard to read these old tiny charts)


But this is for a welding arc

It changes with distance just like it does with a wire. Linearly (at high currents). The temperature of the gas is probobly the main factor for conductivity ? At low currents I don't know. I think its kinda unstable


and
At very low currents it looks like it tops out at about 30 ohms per mm (2-3 amper range)


*keep in mind its i2r, so even if you have decreased resistance, the power of the arc still goes up even if the resistance decreases. I.e. 1kW @ 50A and 4kW @ 250 amps So if that heat is being carried into the work piece you know how a welder works, its like a torch jet. Then you also have the electricity doing something on the work piece, but if you experiment, 50 amps on a piece of steel actually don't do too much ! nothing like the arc heat.

Marco:
From Google :
https://www.researchgate.net/profile/Abdel-Aleam-Mohamed-2/publication/224074690_Direct_current_glow_discharges_in_atmospheric_air/links/55dda7e308ae591b309b7360/Direct-current-glow-discharges-in-atmospheric-air.pdf

According to that, if you current limit at 5ma to keep it not immediately lethal it's about 400kOhm per cm.

A welding arc is a lot lower, it will also blind you and throw a lot of ozone and molten electrode around.

jonpaul:
Hello: Plasma tweeter: waste of time ...dangerous.

Low efficiency, short life, danger f ozone poinsing.

We used RAAL Ribbon tweeters for decades, MUCH better sound.

Plasma imp:
No simple answer.

Read classic books: Gaseous Conductors, Cobine,
J.J. Thompson, etc for arcs.



Jon

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