On Sun, Mar 13, 2005 at 06:12:46PM -0500, David Lesher wrote: > Speaking on Deep Background, the Press Secretary whispered: > > Perhaps someone who knows EE can enlighten me? > > I'll try. > > The #1) is BS. #2) is true. > > If ANYTHING is, it's square waves. [Huh?] > > Virtually all surge protectors have MOV - Metal Oxide Varisters - > within. These are devices with s sharp knee on their Voltage vs > Resistance curve. In other words, they do not conduct for a 120V > level, but do at 200, shunting that overvoltage to ground.
Careful: that conduction voltage is peak, is it not? 120VAC is RMS; the peack voltage is, like, 175, isn't it? > Now, via magic called Fourier, sharp transitions mean lots of short, > high voltage pieces-parts. [trust me, or read up..you can create > any square wave from an infinite series of sine waves..] > > So the ""risk"" I hear talk about is this. The MOV's in a strip > conduct slightly on those squarewavish USP output waveforms. This > results in 2 things, gradual loss of MOV efficacy, as they > degrade slowly with use; and the worry that iffen the MOV's > absorb too much squarewave crap, they'll explode. See, MOV's > turn transients into heat. Line transients are assumed to be err > transient & tolerable. Continuous stuff is another issue...that > can overheat the MOV and cause it to worship the Smoke God. Smoke emitting diodes? > So let's ban surge strips on UPS's...But wait... lots of machines > have MOV's inside their power supplies.. Shhh!!! :-) > But note that the OP does not have a MOV issue; he has an inspector > issue. His best answer there may be buying outlet strips that > offer no surge protection. He likely will need to first pin > the inspector down on what rules he's allegely broken, however. This is the most cogent point to date, and the one I made off list: ask him to quote chapter and verse. Cheers, -- jra -- Jay R. Ashworth [EMAIL PROTECTED] Designer Baylink RFC 2100 Ashworth & Associates The Things I Think '87 e24 St Petersburg FL USA http://baylink.pitas.com +1 727 647 1274 If you can read this... thank a system adminstrator. Or two. --me