Fair enough. So creepage isn't an IPC term, but it could just as well be. Imo,
in this instance it's fluff and does little more than to obfuscate the
underlying principle. Got kids? Okay, then do this, teach the 4yr old that "NO!
It isn't a tree, it's an Oak...Got it?" or "No, Bobby, that's not a car, it's a
Mazda". To me, that sounds like mud, or worse, like unthinking rote.
If one is sharing one's knowledge with someone who is less knowledgeable about
a subject (ie, teaching) a fundamental principle (like, um, say...how to think
about trace spacing, for instance) to someone who is asking for
instruction,(and therefore can be expected to not already know the fundamental
principle, ie, like F=mA, V=IR, Xî=~0.2mil/V {bare board, sea level} or
similar) one does not start by muddying the concept with trivial distinctions,
unless one is either attempting to personally stay atop the proverbial hill as
the sage advisor (aka king-o-dee, like a certain pedantic, scheming dullard
that has fortunately vanished from this group, though in light of my comment
here I would not be surprised to see a sudden re-emergence of said personality)
or simply to keep the student at the bottom of said hill to lower the local
mean, which is not out of the realm of possibility in this civilization at this
econmomic time. Believe as you may, but leakage is leakage. Creepage is simply
a term used by some under CERTAIN circumstances to destinguish a SPECIFIC form
of leakage, and no amount of quibbling will alter the factual reality of that
statement. Look up the definition.
I understand what you're trying to say, and though the tone of my words may
sound as if I do, I mean no personal disrespect. I realize that there is a
place for distinctive terms like this within a particular discussion of
informed individuals, ie, when clarifying the constituents of the leakage
current inherent in a specific process, mechansim, or otherwise to one's team
members. I do not believe though that there is much place for that discussion
at an elemental level, which is, I believe, the nature of the original query,
yes?
<eyes beginning to glaze over>
aj
>-----Original Message-----
>From: [EMAIL PROTECTED]
>[mailto:[EMAIL PROTECTED] On Behalf Of Brad Velander
>Sent: Wednesday, December 13, 2006 6:19 PM
>To: Protel EDA Discussion List
>Subject: Re: [PEDA] 500V power supply
>
>Andrew,
> Your comments are misplaced, "creepage" is not an IPC
>term nor specified in their specs that I have seen/used. My
>understanding is that they conveniently ignore it because it
>goes beyond the circuit board design/fabrication.
>
> Creepage is used by the other regulatory bodies
>(UL/CSA/EU/TUV/etc.). If what you state were true then there
>would be only one leakage spacing spec, but there are are (at
>least) two and they are typically significantly different
>spacings/values. Therefore "leakage" is not "LEAKAGE" (generic
>& all encompassing), is not "creepage".
>
> I was just trying to point out a couple of issues that
>can catch those less knowledgeable. I don't claim significant
>expertise here but I did do a brief stint at an
>internationally reknown power supply/converter company and
>both spacings are different and required by various safety
>compliance regulators. By the way, those specified spacings
>already have an engineering margin in them and don't require
>further margins being added again.
>
>Sincerely,
>Brad Velander
>Senior PCB Designer
>Northern Airborne Technology
>#14 - 1925 Kirschner Road,
>Kelowna, BC, V1Y 4N7.
>tel (250) 763-2232 ext. 225
>fax (250) 762-3374
>
>
>-----Original Message-----
>From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
>Sent: Wednesday, December 13, 2006 2:11 PM
>To: [email protected]
>Subject: Re: [PEDA] 500V power supply
>
>
>Oh, come on...Electrical leakage is leakage Brad. Creepage is a "cute"
>term meant to apply specifically to surface leakage, but it's
>all leakage, as in electrical current flowing unexpectedly
>through a dielectric medium. (call it over if you like, it's
>still "thru" to my physics eye.) That's one of the novel
>things that the IPC brings to the table. Redefinition of basic
>physics into terms that can suit the purposes of
>obsfucation...and of course profit by intellectual ownership
>of originally US-citizen-owned information.
>
>For instance, when I designed an instrument for KLM a couple
>years ago to (amongst other things) measure LEAKAGE from pin
>to pin on a connector, the mode of transport under
>consideration was not leakage across the air gap, but through
>the dielectric separating the contacts.
>
>It's my policy to leave the cute to the IPC, Altium's
>marketing Goo-Roos, and the cabal of "shhhhh...don't tell
>anyone its just water".
>
>And yes, DC or AC, the critical value is the peak value. All
>AC is DC if time passes slowly enough, and most DC is AC if
>you speed the clock a bit. Peak values Carlos. That means not
>only what you expect, but what might be. (Hence the
>engineering margins I spoke of earlier)
>
>Regards,
>
>aj
>
>
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