I haven't been following this thread closely, so if the following has already been addressed, I apologize. I noticed this several years ago at the office building I worked in at the time. My cube moved from one end of the building to another, and my computer wouldn't always start - it took several tries. I brought in a scope, and saw that the ac voltage waveform was flattened. It was more flattened at my new cube than at my old one. Clearly this is related to power supplies recharging filter caps at the peak of the ac waveform, and the relative distance from the building main breaker at the two different cubes. This is a power/crest factor issue, not directly a harmonic issue, although drawing current only near the peak of the waveform will definitely generate harmonics.
>From: John Woodgate <j...@jmwa.demon.co.uk> >To: emc-p...@majordomo.ieee.org >Subject: Re: Unity Power Factor >Date: Wed, Jan 29, 2003, 2:23 PM > > > I read in !emc-pstc that Rich Nute <ri...@sdd.hp.com> wrote (in > <200301291623.iaa07...@epgc264.sdd.hp.com>) about 'Unity Power Factor' > on Wed, 29 Jan 2003: >> >> >> >>Hi John: >> >> >>> >In the USA, this has largely been fixed by a change in >>> >the USA National Electrical Code. >>> >>> There must be quite a number of installations that are not yet upgraded. >> >>Where a problem existed, it was fixed by pulling >>another neutral. > > Yes, we do that, too. >> >>> Are there any other problems appearing in the field which can be >>> reliably determined as due to concentrations of non-linear loads of less >>> than 3 kVA or so? >> >>Probably not. >> >>The only other problem that I know of is distribution >>transformer overheating. But, I believe such >>transformers are very much larger than 3 kVA, so 3 kVA >>of non-linear loads would have very little effect. >> > I mean *concentrations* of loads, individually below 3 kVA or so. > Distribution transformer overheating is the sort of effect that I am > interested in. Are these MV/LV transformers, 'pole-pig' types or larger. > -- > Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk > Interested in professional sound reinforcement and distribution? Then go to > http://www.isce.org.uk > PLEASE do NOT copy news posts to me by E-MAIL! > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > majord...@ieee.org > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: emc-p...@hypercom.com > Dave Heald: davehe...@attbi.com > > For policy questions, send mail to: > Richard Nute: ri...@ieee.org > Jim Bacher: j.bac...@ieee.org > > Archive is being moved, we will announce when it is back on-line. > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc > This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org Archive is being moved, we will announce when it is back on-line. All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
