Re: Break-down voltage of gaps and humidity

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: Tesla729-at-cs-dot-com 

In a message dated 11/13/03 4:43:09 PM Pacific Standard Time, 
tesla-at-pupman-dot-com writes:
>Original poster: "Mccauley, Daniel H" <daniel.h.mccauley-at-lmco-dot-com>
>
>
>
>Regarding humidity and the effect of it on break-down voltage:
>
>In testing, I (as well as others) may have noticed that corona discharge
>increases from a high voltage point in the
>presence of increasing humidity.
>
>However, in Kuffel's High Voltage Engineering text, he states that the
>break-down voltage between two gaps will
>actually increase with increasing humidity.
>
>This seems to contradict what I have experienced.  Can anyone comment on
>this?
>
>Thanks
>Dan


Dan, all,

You bring up a good question that I have also pondered. It is
commonly accepted amongst the list in general that cold, dry
winter days are the best for maximum performance from a
Tesla coil, so it would seem that Kuffel's statement would
be true, if this is the case. Cold air has higher pressure
since it's denser (and I thought increased pressure suppressed
corona) and it definitely has a lower dew point since the dew
point can only reach as high as the ambient air temperature,
and that's only when the RH (relative humidity) is 100%. When the
relative humidity is < 100%, then the dew point is less than the
ambient temperature. It's obvious that 90* F summer air can
hold much more latent moisture before saturation (100% RH)
than 30* F winter air, but warm sticky air is supposed to be the
worst conditions for coiling. There does seem to be a contra-
diction here, when you consider that moisture as well as lower
pressure air (at least until a hard vacuum is reached) are sup-
posed to lend theirselves to better conductance than dry, mois-
ture starved air and air that is under greater pressure. I'll watch
the responses to this thread w/ interest as well.

David Rieben