Rich,
I can see your point. As a result of rapid polarity reversals, the
acceleration of an ion across the mean free path of a gas will be halted
and even reversed. I will read this paper to gain a better understanding
but at this time I believe this will only affect gas breakdown as a result
of impact ionization.
Thanks for the link,
Doug
On Tue, Aug 11, 2015 at 5:08 PM, Richard Nute wrote:
>
>
>
>
> Hi Doug:
>
>
>
>
>
> A simple (and therefore incomplete) explanation:
>
>
>
> Breakdown in air requires the ions to travel from one pole to the other
> before the polarity reverses. At high frequencies, the polarity reverses
> before the ions can travel the distance between the poles.
>
>
>
> At high frequencies (compared to mains frequencies) the clearance can be
> less. See:
>
>
>
> http://lss.fnal.gov/archive/other/ssc/sscl-539.pdf
>
>
> http://ewh.ieee.org/r10/taiwan/pses/archive/2012_04_27/IEEE%20PSES%20April/TC108%20hf_FC_v.1.2_IEEE%20PSES%20TAI.pdf
>
>
>
>
>
>
>
> Best regards,
>
> Rich
>
>
>
>
>
> -- Original Message --
> From: Doug Powell
> To: EMC-PSTC@LISTSERV.IEEE.ORG
> Subject: [PSES] IEC 61010-1 Table K.17
> Date: Fri, 7 Aug 2015 16:47:28 -0600
>
> All,
>
> I am evaluating spacings for an RF product that operates at 13.56 MHz and
> can produce maximum voltages of 5,000 Vrms (7,070 Vpk). If I do an
> interpolation of using Table 6 (Mains 230 V, OV Cat II, indexing on 5,000
> Vrms), I get a minimum clearance requirement of 14.9 mm. When I do the
> same calculation on Table K.17 (column 3, indexing on 7,070 Vpk), I get
> 12.7 mm.
>
> Now I understand the effects of high frequency voltage stress causing air
> molecules to become more energetic and therefore more likely to break down
> at lower voltages. So why in this case does IEC 61010-1 Table K.17 result
> in lower clearance values than Table 6? Somehow, this just seems wrong.
>
> *Please note that in the case of high frequencies paragraph K.3.1
> indicates I am to skip over section K.3.2 with the D1 + F × (D2 – D1)
> calculations.*
>
> Thanks a bunch!
>
> Doug
>
> Douglas E Powell
> doug...@gmail.com
> http://www.linkedin.com/in/dougp01
>
--
Douglas E Powell
doug...@gmail.com
Skype: doug.powell52
http://www.linkedin.com/in/dougp01
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