There are two parameters here - the max continuous rated rms voltage which is normal operations, and the 'clamping' voltage where the component goes low impedance which is abnormal operations. We are talking about the former; and the latter is not necessarily part of any safety requirement - other than the component shall not puke it guts out during an abnormal operating condition.
As most of my stuff is rated for 240V input, the VDR must be rated for 288V min - and this is NOT the clamp voltage. We typically aim for a 450V to 600V clamp level for our standard series power supplies, depending on the market segment. And very much more or very much less for other stuff... Brian > -----Original Message----- > From: [email protected] [mailto:[email protected]]On Behalf Of John > Woodgate > Sent: Saturday, June 05, 2010 2:48 AM > To: [email protected] > Subject: Re: VDR recommendations > > In message <[email protected]>, dated Sat, 5 > Jun 2010, > John Woodgate <[email protected]> writes: > > > > >>Bad things would probably happen if I have to use a VDR > rated at 420V. > > > >Equally, bad things would probably happen if you use a VDR rated at > >less than 420V. Spikes well above 288 V are not that rare on 240 V > >mains. > > Ahem! Are those VDR voltages specified in the standard 'r.m.s. sine > wave' or 'peak'? If peak, which would be logical, the > calculation would > be: 240 x sqrt(2) x 1.2 = 407 V. > -- > OOO - Own Opinions Only. Try www.jmwa.demon.co.uk and www.isce.org.uk > John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK > I should be disillusioned, but it's not worth the effort. - This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <[email protected]> Mike Cantwell <[email protected]> For policy questions, send mail to: Jim Bacher: <[email protected]> David Heald: <[email protected]>
