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 jra@baylink.com 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