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Ask a Geek! Nonlinear harmonics?
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Author | Topic: Nonlinear harmonics? |
147Wiz Geek Larva Posts: 28 |
posted May 31, 2002 20:03
Hi All, I was wondering if any of the computer savvy Geeks out here can However, we upgrade the neutral wire at least one size when the circuits are for desktop computers. Generally we use a #10 AWG When I ask other people such as the foreman or straw bosses at work the answer given is usually "Nonlinear Harmonics and how come you ain't done yet?" and no further conversation ensues. The engineers are never on the site at the same time we are and so I hope somebody here knows the electrical universe that lies beyond the silicon. Thanks
Ed IP: Logged |
Jessycat Geek-in-Training Posts: 35 |
posted May 31, 2002 20:35
quote:
Sorry, must edit: I am theatre-centric, and re-reading your post made me realize that my question made no sense!!! Please ignore it. IP: Logged |
147Wiz Geek Larva Posts: 28 |
posted June 01, 2002 09:18
Hi Jc, The question actually does make sense because my union does have jurisdiction at the Javits Center and I've spent 20 hour days as a production electrician (we're called show extras) doing show lighting for the Auto Show and the Boat Show and things like that. Great money, aching body. Ed IP: Logged |
quantumfluff Highlie Posts: 781 |
posted June 01, 2002 15:10
<rant> I've done a lot of trade shows at the Javitts Center. I will say, with strong conviction, that the whole union system is morally bankrupt. Let's go through a list of problems: Example 1: Our booth was in the center of a 20'x20' carpet and needed lights. Example 2: End of the show. We have a portable booth but we own the carptet rather than renting it. Example 3: We had a complex booth that required assembly and we didnt' arrange with our booth vender for assemblers. IP: Logged |
LifetimeTrekker Assimilated Posts: 466 |
posted June 01, 2002 18:16
Being the research rat I am, I couldn't help but look up the term to try to put some meaning to it in the context of your question. The best clue I had on your scenario comes from: http://www.oulu.fi/~spaceweb/textbook/plhr.html Not being an electrical engineer or physicist, the only suggestion I have is the different materials may be used to avoid the formation of VLF signals coming into the desktop system. If any of you folks more into material science than I can elucidate, I'm a little curious to see the correct answer. IP: Logged |
MrJ Geek Larva Posts: 26 |
posted June 03, 2002 01:38
The question was about the neutral/ground/sinking current, leaving the computer equipment. The bigger neutral wire is meant to handle larger current; wires don't condition the line. Computers have single-phase switching power supplies that use pulse loads. The supply changes impedence to grab the peaks of the sine wave voltage, which is the nonlinear part. All the switching causes the harmonics (multiples of the frequency). With balanced three phase power distribution, normally the current waves of each phase cancel on neutral. However the 3rd harmonics (and other odd multiples) caused by the switching don't cancel and can add up to significantly higher currents on the shared neutral (try a switched load on each phase). The best explanation I found was here, along with many solutions: Brief explanation and things that can go wrong: Brief explanation and a little math (max neutral current): IP: Logged |
147Wiz Geek Larva Posts: 28 |
posted June 03, 2002 17:50
LT and MrJ-- Thanks to both for your help. The web sites were very interesting. I haven't visited Fourier Analysis since my networks courses in the early sixties and I seem to have forgotten everything. At last, some use for this stuff!
I do hope your shows are successful and you make enough for the aggravation to be worth it.
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