Re: [PSES] IEC 61010-1 Table K.17

2015-08-12 Thread Doug Powell 
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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[PSES] FCC label - stick-on / permanently affixed ....

2015-08-12 Thread Amund Westin 

FCC CFR 47 §15.19   Labelling requirements: The label shall not be a
stick-on, paper label. The label on these products shall be permanently
affixed to the product and shall be readily visible to the purchaser at the
time of purchase, as described in §2.925(d) of this chapter. “Permanently
affixed” means that the label is etched, engraved, stamped, silkscreened,
indelibly printed, or otherwise permanently marked on a permanently attached
part of the equipment or on a nameplate of metal, plastic, or other material
fastened to the equipment by welding, riveting, or a permanent adhesive. The
label must be designed to last the expected lifetime of the equipment in the
environment in which the equipment may be operated and must not be readily
detachable.


 

 

My interpretation:

Stick-on, paper label is a label with paper surface. Such type of label can
be damaged when exposed to humidity, water, etc.

I have a lot of devices (here at the office) with FCC label and many of them
have stick-on labels. But, they have plastic, vinyl, etc surface. Such a
label will be more resistant than a paper label. But still it’s a stick-on
label.

In my opinion, it will be good enough to use a stick-on plastic label with
permanent adhesive. The last question can be «what is permanent adhesive?».

 

Any comments?

 

Best regards

Amund

 

 

 

 

 


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