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:[email protected]] Sent: Wednesday, February 20, 2002 11:16 AM To: [email protected] Cc: [email protected]; [email protected] 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 ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list" ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on "browse" and then "emc-pstc mailing list"
