I know that one should not advertise BUT  I think that Claude Lyons 
(b...@lyons.demon.co.uk) has a solution to this by injecting a difference 
current to balance the distortion. I simple terms like the Current Dumping 
amplifiers.

Comments Bill?
  -----Original Message-----
  From: owner-emc-p...@majordomo.ieee.org 
[mailto:owner-emc-p...@majordomo.ieee.org]On Behalf Of cherryclo...@aol.com
  Sent: Wednesday, January 23, 2002 5:27 AM
  To: ghery.pet...@intel.com
  Cc: emc-p...@majordomo.ieee.org
  Subject: Re: EN 61000-3-3 compliant heater controller


  Dear Ghery 
  I am well aware of the undersized neutral problem, but given that we have a 
legacy of buildings with undersized neutrals it is not a simple or low-cost 
solution to uprate all their neutrals. 

  Anyway, harmonics in the mains distribution cause many more problems than 
simply overheating neutrals – waveform distortion is a greater worry. 

  Since your negative approach to the need for harmonics control was similar to 
views expressed in an article in Conformity Update 08-06-00, I originally 
quoted from Mr van den Bergh's reply to that article. 

  Mathieu van den Bergh is not just any ordinary old consultant, he is a member 
of the TC77/SC77A Working Group that is responsible for IEC 61000-3-2 and 
appears to have a great deal of experience and knowledge in the area of 
harmonics. 

  He is also based in the US, where most of the 'denial' of harmonics problems 
seems to arise, despite well-known problems with harmonics in the USA. 

  I would have assumed that since you are knowledgeable in the field of 
harmonics you would already know Mr Van den Bergh and would already have 
discussed your concerns with him and (hopefully) come to some kind of 
agreement. 

  Since he appears to be an expert in these matters, I hope you will not mind 
me quoting a little more from his August 19 2000 reply to Conformity Update: 

  "A number of studies in countries including Switzerland, the UK, France, 
Scandinavian countries, Japan, and the USA, have shown that harmonic distortion 
has increased from about 2 - 2.5% in the late 70's - early 80's to about 4 - 
4.5% in the mid-late 90's with distortion in heavily industrialised areas 
reaching 6 - 7%!! 
  It has also been proven through many studies and observations that harmonics 
related problems increase significantly when distortion levels exceed 5% and 
that they become very serious and costly when distortion approaches 10%. It has 
been generally accepted therefore that distortion is increasing at 0.1 - 0.15% 
per year in industrialized nations. 
  If no action is taken it is to be expected that distortion levels will start 
to exceed critical levels within a few years." 

  Notice Mr van den Bergh is referring here to waveform distortion, not neutral 
currents or zero-phase flux in transformers, both of which are problems only 
for individual sites not the distribution network as a whole. He goes on... 

  "The proliferation of electronic equipment with switch mode supplies falls in 
the same category as the lighting related problems about 20 years ago." 

  I agree with you that the harmonics problem can be ameliorated by actions 
taken at the power distribution network level, or by actions at the load level, 
but I have not investigated their relative economic cases. 

  But whichever method is adopted, the customer pays the bill eventually and I 
have more confidence in the highly competitive world of electronic products to 
come up with a cost-effective solution in a timely manner. 

  I have some knowledge of power-factor correction techniques in switch-mode 
supplies, and some of them can cost very little indeed. So I really don't know 
why the US computer industry is making such a fuss about controlling harmonic 
emissions. 

  It reminds me of the fuss the auto industry made about compulsory seat belts, 
catalytic converters, etc., or the fuss the VDU monitor industry made about 
meeting MPR2 – all those things that were stridently opposed by manufacturers 
as needless added expense, or even impossible – yet we now find them in all the 
products we buy even though they still cost less in real terms than they did 
before. 

  I suspect the real reason for the computer industry's denial of harmonics 
problems, or else blaming them on a poor distribution system, is that US 
computer manufacturers simply want to make one model they can sell world-wide – 
so they want whatever is permitted in their main market (the US) to be 
permitted everywhere else. 
  Would you agree with this? 

  Regards, Keith Armstrong 

  In a message dated 22/01/02 17:34:47 GMT Standard Time, 
ghery.pet...@intel.com writes: 


    Subj:RE: EN 61000-3-3 compliant heater controller 
    Date:22/01/02 17:34:47 GMT Standard Time 
    From:    ghery.pet...@intel.com (Pettit, Ghery) 
    Sender:    owner-emc-p...@majordomo.ieee.org 
    Reply-to: ghery.pet...@intel.com (Pettit, Ghery) 
    To:    cherryclo...@aol.com ('cherryclo...@aol.com'), 
ghery.pet...@intel.com (Pettit, Ghery) 
    CC:    emc-p...@majordomo.ieee.org 

    Keith, 

    Many times the neutral cable problems result from using a smaller gauge 
wire for the neutral in the mistaken assumption that the neutral doesn't carry 
any significant current (true if the 3 phase load is balanced - when did you 
last see that?).  Harmonics may make that problem worse, but the fundamental 
frequency current can be a problem, as well.  The solution, used by many 
building designers, is to use the same size wire for the neutral as for the 
phase conductors. 

    Do you expect me to believe that personal computers cause significant 
harmonics problems?  There is no evidence of this in the U.S.  If there is in 
Europe, then you are admitting that your power distribution system design is 
deficient.  Lousy design on the part of the power providers is fixed by 
saddling the manufacturers of the load with the full expense of the solution?  
Sorry.  I don't buy that approach.  A facilities solution is usually more 
economical than fixing the 'problem' at each individual load. 

    Quoting a few consultants is nice, but doesn't prove a case.  I remain a 
total skeptic on this matter.  IEC 61000-3-2 needs (and is getting) a complete 
overhaul.  IEC 61000-3-3 should be withdrawn.  Flicker is real, no doubt, but 
this issue gets more attention than it deserves in the home environment. 

    Ghery Pettit 

    -----Original Message----- 
    From: cherryclo...@aol.com [mailto:cherryclo...@aol.com] 
    Sent: Tuesday, January 22, 2002 2:23 AM 
    To: ghery.pet...@intel.com 
    Cc: emc-p...@majordomo.ieee.org 
    Subject: Re: EN 61000-3-3 compliant heater controller 


    Dear Ghery 
    There is plenty of evidence, for harmonic problems, especially in large 
cities and large office buildings. 

    For example, an electricity supply engineer told me that in the financial 
district in London there are buildings where they cannot fit any power factor 
correction capacitors to the fluorescent luminaires - because they fail within 
days due to the waveform distortion caused by harmonic currents. 
    So they have buildings drawing 100's of kA of lighting current at a low 
power factor (< 0.6 I understand). I also understand they have overheating 
problems with cables under the Thames connecting the two halves of London, due 
to harmonic currents. 

    In the early 90's I spoke with a USA-based consultant who told me about a 
number of problems (e.g. completely burnt-out neutral cables) he had seen in 
buildings in the US where they had installed lots of single-phase equipment. 

    'Banana Skin' No. 102 in the EMC + Compliance journal, Oct 2000 (read it in 
the archives at www.compliance-club.com) describes harmonic overheating 
problems with low-voltage lighting installations in hotels and public buildings 
that has Fane Murray, a lighting consultant in the UK, very concerned indeed. 

    I understand that the power distribution in the USA is generally less 
susceptible to waveform distortion than in Europe, nevertheless I understand 
that the US has its own harmonics problems – Mathieu van den Bergh, of Computer 
and Networking Services Inc., California said in August 2000: 

    a)  for many years the US has had IEEE-Std-519 which has recommendations 
for harmonic limits which are not much different from IEC 61000-3-2; 

    b) the US lighting industry has voluntarily implemented ANSI harmonics 
standards for fluorescent lamp ballasts that are more stringent than IEC 
61000-3-2, as the direct result of serious harmonics problems in large office 
buildings; 

    c) the US Government has issued several large scale procurement 
requisitions for Information Technology  that included far more stringent 
harmonics requirements than those in IEC 61000-3-2. 

    Time does not permit me to go through my files to provide a longer list of 
real-life problems with harmonics. 

    Regards, Keith Armstrong 
    R>In a message dated 21/01/02 23:54:36 GMT Standard Time, 
ghery.pet...@intel.com writes: 


      Subj:RE: EN 61000-3-3 compliant heater controller 
      Date:21/01/02 23:54:36 GMT Standard Time 
      From:    ghery.pet...@intel.com (Pettit, Ghery) 
      Sender:    owner-emc-p...@majordomo.ieee.org 
      Reply-to: ghery.pet...@intel.com (Pettit, Ghery) 
      To:    j...@jmwa.demon.co.uk ('John Woodgate'), 
emc-p...@majordomo.ieee.org 

      So rather than educating the public on the cause of flicker, we get 
saddled 
      with a useless design requirement.  Typical bureaucracy - don't fix the 
      problem, make it LOOK like you're doing something, at someone else's 
      expense.  Just like the harmonics standard - fix a problem that doesn't 
      exist. 

      Ghery Pettit 


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