After googling i found myself reassured that power factor was 0.8 or better for most linear power supplies, but both effiency and harmonics wer bad for linear power supplies.
I googled for your article also but could only find a reference to it, not the article itself. would you be so kind as to provide the schematic some way that i can find it?
** 5. harmonics have no direct impact on neutral currents. ***
What do you mean by *direct* ? I imagine you mean not for single phase circuits ?
Their resultant effect on three phase circuits is *precisely* why they have come in for legislative atttention.
Graham
Your definition sounds a lot like efficeincy, Please see this:
Yes, harmonics can produce increased neutral line currents. This is the leading reason that almost all 3 phase transformers are designed as "delta-wye"; the delta winding "shorts out" the 3rd harmonic (with a major redirection of the 3rd harmonic currents to the "line" conductors.
This is a very useful article. Clear, correct, and reasonably complete for high grade general to inexperienced engineer consumption. Thanks for the pointer.
reply was interstitial.
I allow that you disagree, however my IEEE dictionary is at work and i am at home. it may include other factors than V-C phase angle, but that angle is what almost all engineers use.
Actual Watts to VA is also a reasonable definition and includes other power distribution issues. It also more resembles power transport efficiency (in general a somewhat different kind of measurement). Just the same, the original useful definition was the phase angle of the fundamental frequency.
Then why does the initialism expand to "Power Factor Correction"? see:
reply was interstitial
It's simply what the semiconductor industry decided to call it.
So-called PFC is there *entirely* to minimise harmonics.
I suggest you read EN61000-3-2 for example.
Graham
At least in part, consumer electronic equipment was driving the harmonics issue with brute force; transformer, rectifier, capacitor type bulk power supplies (from the 60 through the early 90's). Both earlier fluorescent lighting, and typical mercury vapor and high pressure sodium lamps produce harmonics as well.
I have rechecked my reference books, and retained literature. In wye configurations (typical secondary winding connections) harmonics do cause problems with harmonic neutral currents. Delta configurations essentially "short out" the 3rd harmonic currents (which is why the primary is usually "delta"). That is still help for the secondary currents (moving part of the harmonic currents to the line to line mode. Ok, you get some more transformer losses).
That is both impolite and irrelevant.
And you cannot release a proper pointer to your published design for others to evaluate for what reason?
I have had access or my own copies of magazines such as EDN, Electronics, Computer Design, et cetera for over 40 years, your publication in a Australian does not mean that every electrical engineer on the planet had access to it any more than publication in EDN or IEEE spectrum. "Electronics Australia" is just another industry magazine to me.
The word "efficiency" does not appear in that article, but this does. "Loads with highly distorted current waveforms also have a very poor power factor; because of this, they use excessive power system capacity and could be a cause of overloading. Voltage source electronic adjustable speed drives (ASD) often have a total power factor of approximately 65% because of the highly distorted current."
That sounds like a direct contradiction of 5.
Glad to be of service.
JosephKK wrote: (snip)
Yes. The harmonics heat the delta transformer windings because the circulate there, requiring transformer derating with highly harmonic 3 phase loads. That is a direct effect.
"JosephKK"
** WRONG - PF is merely the ratio of watts to VA in a load.Your definition is *restricted* to "all sine wave" systems ONLY !!!
** Nonsense - PFC is *intended* to reduce or eliminate harmonic currents. ** Huh ??? ** This guy *cannot* be an engineer ?? ** See above. ** Ought to be de-registered............ Phil
"JosephKK"
** Might as well go cook a google egg if that is all you can discover. ** My "RMS Current Monitor" design was published in "Electronics Australia " ( a technical magazine ) - not on some stinking web site.The material is copyright to myself and the mag.
......... Phil
"JosephKK"
** You nothing but a posturing ass.The *general definition* of PF is in ANY electrical text printed in the last 100 years.
The "cos (Phi )" formula is a derived definition.
** Because harmonic currents due to electronic loads increases the VA figure for the same watts level - so makes the PF figure worse. The "A" in "VA" is an *** rms *** measurement as is the "V".You must consider the increased rms value of pulsed current waveforms compared to sine waveforms.
** Ought to be de-registered - NOW !!!The fool is a public menace !!
........... Phil
** Crap.
** My gawd - the damn thing was published in a magazine with a readership of over 40,000 !!!
The only reason I mentioned it is that is measures the "rms" value of the AC supply current draw - as used in "VA"
Know what that is ?
So I know the VA or every item I run tests on.
Got a clue how rms and average rectified values compare for different wave shapes ??
PF = VA / watts
Capice ??
......... Phil
Have something to add? Share your thoughts — no account required.
Ask the community — no account required