I don't believe I have seen anyone else point out that the spacing
requirements are typically specified for DC (RMS). Any AC, pulses or spikes
have to be suitably considered at their "peak" values. That 'typically' bumps
you up at least one voltage rating/spacing category.
I would say that you really need to read IPC-2221 section 6.3, as a
minimum.
Besides that there is a lot of other information from safety regulators
like UL/CSA/EU/TUV, more specifically towards product safety and power supply
design. With the safety regulators it typically gets even more complex because
they start taking into account environmental pollutants (humidity, dust or
other particles which can compromise the spacing) and applying
pollutant/environment categories. Andrew mentions "leakage" and leakage has two
forms. Leakage is typically through air or an air gap, "creepage" is across
surfaces and is equally important in most cases.
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 1:15 PM
To: [email protected]
Subject: Re: [PEDA] 500V power supply
Exactly. Be careful that you don't think "ideally". Think instead
cautiously. Cautious is wider spacing. Do not go under, as you will not
necessarily see any immediate problem, even though there may very well
be a major problem. (leakage)
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