[Amps] Direct rectification of AC mains to drive the amp,

[Jim Brown]

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.