--- In Repeater-Builder@yahoogroups.com, "kb9bpf" <[EMAIL PROTECTED]> wrote: > > Since I'm way more into RF than industrial power distribution, I've > always been able to think of "power factor" on the electrical power > grid in terms similar to antenna system reflections, which are > commonly measured in terms of SWR. After all, both are AC systems > where the voltage and current bear a phase relationship to each > other. > > When they are perfectly in phase the power factor is 1.0, and a 60-Hz > SWR meter would measure 1:1. When they are out of phase (power factor > <1) that SWR meter would read greater than 1:1. I suspect, though I > haven't done the math or looked up the specific matahematical > definition of power factor, that it would be direcly proportional to > the reciprocal of the power factor. And as we know, when that happens > the power generating end has more difficulty delivering power > efficiently to the load. >
A while back I was doing some analysis of power factor to understand it better and I found that it has a lot in common with SWR. Both are focused on the issue of power transfer, so I guess we shouldn't be surprised. The thing they really have in common is for max power with AC signals, the voltage and current need to be in phase (phase angle of zero). For linear systems with nice sine waves, PF = cos (phase angle) where phase angle = the angle between voltage and current sinusoids Wikipedia has a good explanation of PF at http://en.wikipedia.org/wiki/Power_factor Play around with some typical circuits and you'll find that an SWR of 1 also has voltage and current in phase. Again, not a surprise since it represents the best power transfer. This is from memory, so the usual disclaimers apply :-) 73, Bob K0NR
