# Re: Current Limiting and Impedence/Phase angle of an 18khz argon discharge?

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• Subject: Re: Current Limiting and Impedence/Phase angle of an 18khz argon discharge?
• From: "Tesla list" <tesla@xxxxxxxxxx>
• Date: Thu, 28 Apr 2005 10:44:21 -0600
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• Resent-date: Thu, 28 Apr 2005 10:51:38 -0600 (MDT)
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`Original poster: "Gerald  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>`

`Hi Harvey,`

I'm afraid I'm not an expert on ionizing gases. I do believe they are negative resistance and once the ionizing voltage is reached, the resistance of the gas goes from very large to very small. Neon sign transformers are current limited for this reason. I have heard that on say a 15KV NST system that once the neon sign conducts, the voltage across the neon tube drops down to maybe in the 100's of volts.

Here is one thing to keep in mind when you repeat your experiment. For cases where time varying magnetic fields coupling into a circuit loop can be neglected, the sum of rms voltages around a loop, in general, will not be zero even though (Kirkoffs voltage law) the sum of the instantaneous voltages will be zero (or close to zero). For example, you can devise an AC circuit with inductive and capacitive reactance where the rms voltage (wrt ground) of node A and node B are the same, yet there is an rms voltage between node A and B.

`Gerry R`

`Original poster: Harvey Norris <harvich@xxxxxxxxx>`

```--- Tesla list <tesla@xxxxxxxxxx> wrote:
> Original poster: "Gerald  Reynolds"```

```> >Instead we must break down the Z's into R, and X
> >
> >Z1^2 = R1^2 + X1^2
> >Z2^2 = R2^2 + X2^2
> >
> >And must assign the correct sign for X in case both
> inductive and
> >capacitive reactance is present.
> >
> >Then
> >
> >Z^2 = (R1 + R2 + ...)^2 + (X1 + X2 + ...)^2
>
> YES, this is correct
>
>
> >I'm not sure this solves my problem, because in my
> case the R's were
> >near zero and the X's were inductive.  I will go
> back and recalculate.```

```Hi Gerald, I had a similar problem where two
impedances were added in series, and I was wondering
if the following data would provide enough information
to determine the acting phase angle of a gas
discharge, which in this case was a 2 ft argon tube.
First let me digress a bit about what I have seen with
gas disharges. We all know that a gas discharge must
be current limited or ballasted. But why is this
msnip....
```