And, to add to what Jim has said, I can only guess what would happen to
sensitive, or not so
sensitive, electronics, internal wiring or electromechanical parts when an
open-air discharge occurs
inside a product, especially a shielded product. Erratic behavior may be the
lesser of what could
happen.
IMO, such electronics and/or parts might need to be really hardened against
such an event, depending
on the severity of the event. So, a few cents might have been saved on the
spark gap, but.....
Comments?
Best regards,
Ron Pickard
rpick...@hypercom.com
jim.eich...@xantrex.com
Sent by: To:
emc-p...@majordomo.ieee.org
owner-emc-pstc@majordom cc:
o.ieee.org Subject: RE: Using PCB
traces as transient voltage suppressor
02/20/02 02:10 PM
Please respond to
Jim.eichner
Isn't the other issue here that creepage and clearance are normally required
between live parts and from live parts to ground?
If you buy components, you can go get approved components.
If you do it yourself on the board, you're going to invoke all kinds of
extra approvals work - evaluating your home-made spark gap to the standard
for transient voltage suppressors, or your home made fuse to the standard
for supplemental fuses, or...
Regards,
Jim Eichner, P.Eng.
Manager, Engineering Services
Xantrex Technology Inc.
Mobile Power
web: www.xantrex.com <http://www.xantrex.com>
Any opinions expressed are those of my invisible friend, who really exists.
Honest.
-----Original Message-----
From: Rich Nute [mailto:ri...@sdd.hp.com]
Sent: Wednesday, February 20, 2002 11:16 AM
To: chris.maxw...@nettest.com
Cc: gab...@simex.ca; emc-p...@majordomo.ieee.org
Subject: Re: Using PCB traces as transient voltage suppressor
Hi Chris:
> 1. Can anyone else verify the breakdown voltage of 1Megavolt/meter for
> air? Seems different than what I can remember; but I don't have a
> reference handy. It also seems to me that this would be very dependent
> upon humidity and pollution degree?
In a separate message, I will send you the air
breakdown voltage curves from IEC 664.
Humid air has a very slightly higher electric
strength than dry air. (Water vapor, a gas,
has quite different properties than water as
a liquid.) I believe air temperature has more
effect on electric strength than does humidity.
Pollution affects the electric strength of
the scheme because it is deposited on the
electrodes. This tends to reduce the electric
strength between the two electrodes. This is
a larger effect than humidity.
The biggest factor affecting the electric
strength of air is air pressure. Pollution,
temperature, and humidity have relatively
low effects.
Best regards,
Rich
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