On 9/22/2013 10:10 PM, Jim Thomson wrote:
Has anybody actually measured the PF on a transformerless supply, with
a big C filter ???
I cant see it being any worse than your typ kw tube amp....with the
typ xfmr + FWB / Doubler +
high C filter.
No, but the issue is not reactance, it is the fact that current is not
sinusoidal, but rather is drawn in pulses at the peaks of the cycle to
charge that cap. Back when most of us went to school PF was simply
related to the phase angle between the sine wave of voltage and the sine
wave of current. Now, the definition of PF has been expanded to include
that impulsive current.
Also the current is impulsive,so it is rich in harmonics, and "triplen"
harmonics add in the neutral of 3-phase systems. Because the loads on
electrical systems are now dominated by equipment of all sorts with
capacitor-input filters, and triplen harmonics add in the neutral of
3-phase systems, it has become all too common for currents in the
neutral of 3-phase systems to be equal to or greater than the phase
currents. Remember "the towering inferno?? The cause was overheating
neutrals, and flames were burning insulation that spread up raceways.
In EU, power factor is regulated by electrical codes. In North America
it is not, although I think I've heard that power companies may offer
discount rates for maintaining a better PF.
73, Jim K9YC.
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