> It's crazy, John. SMPS don't take a simewave current, they take a
> short pulse on the peak of the voltage.

JT> No, they take a short pulse BEFORE and UP TO the peak, It isn't
JT> symmetrical around the peak, so it somewhat can be called a
JT> capacitive load. 

 Have a look some time... the pulse straddles the peak. As the
current-pulse charges the capacitor, the output voltage rises to meet
it, which crosses the peak unless there is *zero* source resistance
in the circuit.

 But in any case, I was speaking about the pulse itself, not its
precise placement. A pulse *anywhere* in the sinewave cannot be PF
corrected. The point of PF is that the generator ougth to be loaded by
the same in-phase waveform it produces, or it makes the generator
"cog" and run unevenly.

 The only solution for a pulse load is to shift the phase of the
*supply* to each house (or street, whatever), so that the loads
average out.

> Power factor correction has no meaning unless you filter the
> pulse with a ballast choke like a fluorescent light.

JT> Kinda, there are "passive" designs around that effectively
JT> shift the pulse later, it isn't perfect, but plenty good enough
JT> to keep the power authorities happy.

 So far... because the main drain is resistive hot water and motors,
but when SMPS rules okay, they're going to have to get serious. The PF
spec is just silly.

JT> Just repeating what I've heard, though, since then, there are
JT> still plenty of (current model) 500+W PC power supplies that
JT> aren't power factor corrected. 

 The reality is that *none* of them are... is terms of what they
call power factor correction actually reducing norty loads on the
generators. It's a joke that we go along with because it makes someone
who writes the stupid specs, happy.

Regards,
Bob

 

--- BQWK Alpha 0.5