To David,

 

At a power factor of 0.5 the power meter just

measures 50% of your assumed power.

(but you meant to say write of course)

I agree that the power utilities always try to rip us

off, but they have more sophisticated means

than denying physics.

 

 

I have personally been involved  in measuring

over 40 amps of neutral conductor (@150 Hz) current 

in a building stuffed with ITE equipment,

where only 10-16 A rms per phase was 

measured.  The neutral conductor was a

1.5 mm2 wire, and the phase conductors

were 2.5 mm2

 

So I assure you that harmonics can be hazardous if ignored.

 

To John:

“ Limiting apparent power requirements” 

Right and “harmonics current” is another way of saying that.

 

“ the I^2R losses represent an economic loss to the industry, but the supply
industry experts say it is not a significant issue” 

 

But I personally would be more than happy getting paid the insignificant
amount of

money lost by I^2R losses !!! ;<))

 

A IGBT costing less than 5 dollars per phase is able to control

a load of 10 kW easily at say 5 or 10 kHz.

It is not even difficult to have a power factor of 1 with the right

Topology.  You will need large inductors to smooth out

the switching frequency or active power factor correction 

circuits that at a nominal current level of 10-20% of the

mains current to be corrected, are able to smooth all

current irregularities, so a pure sinus current in phase

with the mains is consumed.

The power loss is about 0.5 % of the corrected power stream

as the injected current is out of phase in the opposite way

as the harmonics of the main power  stream, and as these

devices are also switched, and have an efficiency  of

90% or better.

 

Gert Gremmen

 

 

 

 

Van: emc-p...@ieee.org [mailto:emc-p...@ieee.org] Namens Spencer, David H
Verzonden: maandag 26 april 2010 13:31
Aan: EMC-PSTC@LISTSERV.IEEE.ORG
Onderwerp: RE: [PSES] Harmonic Emissions Testing

 

My understanding was that the harmonics standards were largely driven by the
power utilities and billing.

With a power factor of 0.5 they were only billing 50% of the power consumed.

That examples of large voltage drops on the neutral-ground bus bar in service
panels were exaggerated or anecdotal.

 

However that could be hear say or heresy   ;)

 

 

David

 

 

 

 

 

 

 

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