Residental mains wiring questions (USA)
in [Design]
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From: m II on 3 Jul 2010 18:07 m II wrote: > I'm guessing that if all the waves were the same shape, it wouldn't > make a difference. I'd like put that thought on hold for a bit. I just had a horrible vision of being attacked by mutant, square shaped things. They were mocking me. mike
From: John Larkin on 3 Jul 2010 18:12 On Sat, 03 Jul 2010 16:04:11 -0600, m II <c(a)in.the.hat> wrote: >John Larkin wrote: > >>> In 3 phase, You have to have all three hots feeding a load equally >>> before the neutral balances out. > >> >> IF the loads are sine waves. > > >I'm guessing that if all the waves were the same shape, it wouldn't >make a difference. > >Start putting a different shaped wave or one of a different period on >each phase and then it's a different ballgame. > > The classic set-the-office-partition-on-fire situation is to have a y-connected 3-phase system, with a common neutral, and run a bunch of PCs off each phase. The PCs pull current at the peak of the AC line, at six different times each cycle, so even if the three load currents are equal and have the same waveshape, they don't cancel in the neutral. John
From: John Larkin on 3 Jul 2010 18:13 On Sat, 03 Jul 2010 16:07:20 -0600, m II <c(a)in.the.hat> wrote: >m II wrote: > >> I'm guessing that if all the waves were the same shape, it wouldn't >> make a difference. > > >I'd like put that thought on hold for a bit. I just had a horrible >vision of being attacked by mutant, square shaped things. From three different directions? John
From: bud-- on 4 Jul 2010 12:49 On Jul 3, 5:12 pm, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > On Sat, 03 Jul 2010 16:04:11 -0600, m II <c...(a)in.the.hat> wrote: > >John Larkin wrote: > > >>> In 3 phase, You have to have all three hots feeding a load equally > >>> before the neutral balances out. > > >> IF the loads are sine waves. > > >I'm guessing that if all the waves were the same shape, it wouldn't > >make a difference. > > >Start putting a different shaped wave or one of a different period on > >each phase and then it's a different ballgame. > > The classic set-the-office-partition-on-fire situation is to have a > y-connected 3-phase system, with a common neutral, and run a bunch of > PCs off each phase. The PCs pull current at the peak of the AC line, > at six different times each cycle, so even if the three load currents > are equal and have the same waveshape, they don't cancel in the > neutral. > > John Rectifiers generate harmonics (no surprise). The "triplen" harmonics - 3rd, 6th, 9th, ... - add instead of canceling on a 3-phase wye neutral. -- bud--
From: ehsjr on 5 Jul 2010 00:24
John Larkin wrote: > On Sat, 03 Jul 2010 16:07:20 -0600, m II <c(a)in.the.hat> wrote: > > >>m II wrote: >> >> >>>I'm guessing that if all the waves were the same shape, it wouldn't >>>make a difference. >> >> >>I'd like put that thought on hold for a bit. I just had a horrible >>vision of being attacked by mutant, square shaped things. > > > From three different directions? > > John > With their harmonicas. Ed |