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Date: 01/22/02 at 4:44 PM
Posted by: Lisa Dye
E-mail: ldye@sensidyne.com

In Reply to: Re: High Voltage Board Design posted by DC on 01/22/02 at 1:55 PM:

Your project engineer should be able to specify applicable standards and clearance requirements to you. If your company has established contact with a certification agency or NRTL, they may fax copy of clearance tables to you. Test reports and agency files for existing products are good place to glean applicable standards and engineering contact names. Note that many standards have been or are being superceeded with harmonised versions. Agency contact can help you on this.

Here are some electrical safety standards of note for general purpose equipment:

Info Tech Equip - UL 1950 Tables 3 thru 6A
Indust Ctl Equip - UL 508 Tables 36.1 thru 36.4
Power Units other than Cl 2 - UL 1012 Tables
28A.1 thru 28A.2
Class 2 Power Units - UL 1310 Tables 22.1 - 22.2
Signaling Devices and Systems - UL 2017 Table 18.1

Household and light-industrial equipment IEC 335-1 Table 13:
Clearance for 130-240 volt supply (except at
board edges)
2mm between live parts of different potentials
4mm Hi-potential to earth gnd
8mm Hi- to Low- potential circuits

General Rule for PCB spacing (Clause 29):
150V per mm (min 0.2mm) if protected from dirt deposition; 100V per mm (min 0,5mm) if not protected.

Insulation, encapsulants and risk of contamination will also affect spacings. There are often add'l clearance requirements imposed between component bodies and adjacent conductors.

I can provide certification links if you would like.

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