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Re: power factor correction

Original poster: "Gerald  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>


Hi Dan,

Good question. True power is Irms * Vrms * Power Factor (PF). If the load is resistive, the PF is 1.0 If the load is purely inductive, the power factor is 0.0 and line current will be drawn but no power dissapated and the KWH meter will not spin. Same goes for a purely capacitive load. Line current in both inductive and capacitive cases exists but lags 90 degrees for the inductive load and leads 90 degrees for the capacitive load. The power factor can be expressed as a cos function where:

PF = cos(phase difference between the line_voltage and line_current)

If the load is resistive, the phase difference will be zero and PF=1.
If the phase difference is either 90 or -90 degrees. the PF=0

Most of the time when reactive loads are present, there will be some resistance and this is the part of the load that dissapates power. Can't dissapate power in a pure inductor or capacitor.

Gerry R

Original poster: Dan Kunkel <dankunkel@xxxxxxxxx>

Gerry,

allow me to play devil's advocate here...
if you are reducing line current and not tripping breakers because of
your PFC's, then it seems to follow that you are in fact using less
power. maybe an explaination of true power is needed.

Dan


On Sat, 12 Feb 2005 22:46:52 -0700, Tesla list <tesla@xxxxxxxxxx> wrote:
> Original poster: "Gerald  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
>
> Hi Dan,
>
> I dont think the PFC will effect the electric bill since the KWH meter
> measures true power.  It will reduce the line current and help keep
> breakers from tripping for coils that draw high enough power.
>
> Gerry R.
>
> .
> >Original poster: Dan Kunkel <dankunkel@xxxxxxxxx>
> >
> >PFC's are NOT required, they just help to bring the voltage and
> >current in phase with each other, there by reducing total current draw
> >from you electric company and lowering you electric bill. this is
> >important for home air conditioners, fridgerators etc...
> >
> >hope this helps,
> >Dan
>
>