Re: [Amps] Power factor correction

[Larry Benko <xxw0qe@comcast.net>]

Nothing is missing here at all.  I posted the industry accepted formula 
for power factor here a few days ago.  You can find it on Wikipedia.  A 
few minutes with LTSpice will show that the power factor can be improved 
to nearly 100% by guaranteeing that there are no line side harmonics and 
that the voltage and current (fundamentals) are in phase.  This harmonic 
reduction can be done anywhere in the circuit that achieves the line 
side goals.  The problem is that the passive circuitry to achieve a high 
power factor is large (expensive) and only is optimized at one load 
current and that may be a problem.  Look at any of the "good" (as in 
with real specs) switching power supplies and you will see that the 
power factor for these also varies with load but not by the amount that 
brute force solution does.
I think that most of the people discussing this topic to the point of 
ridiculousness would understand it easily if they would learn how to use 
any of the several free circuit analysis programs available and analyze 
various types of supplies.
73,
Larry, W0QE

On 3/12/2013 8:09 PM, Bill Fuqua wrote:
>  "passive inductive correction on a rectifier/capacitor input system "
>   Does that make it an inductive input filter system?
> Let's see. if the inductor is between the rectifier and the
> capacitor that makes it an inductive input filter.
>   Is there more information on how they do this?
> It seems that if you put an inductor on the AC side of things, even
> on DC side, you would have less output from capacitive input filter.
> Something is missing here.
>    You could improve the power factor by placing a low pass filter 
> between
> AC power line and power supply, thus no harmonic current on AC power 
> line.
> However, there are trade offs in doing that.
> 73
> Bill wa4lav
>
>
>
>
>
> At 10:42 PM 3/12/2013 +0000, Steve Thompson wrote:
> > jeff, wa1hco wrote:
> > >Using a power factor correction cap works when the load is a bunch 
> > of inductive motors. But it >won't really work for the pulse type 
> > load from a capacitor input filter.
> > My first reaction would be to agree with you, but researching PSUs for
> > a quote the Vicor 4kW Megapak was in the frame - that uses passive
> > inductive correction on a rectifier/capacitor input system and claims
> > 0.92 PF in the spec. OK, that's a bit lower than the 0.95+ that active
> > circuits manage, but there's a trade off against complexity and
> > reliability.
> >
> > Steve
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