[RE-wrenches] power factor

[boB Gudgel]

Drake Chamberlin wrote:
> One question about power factor:
>
> We know it is the ratio of the real power to the apparent power, and 
> that most utility meters only register real power (watts).  Reactive 
> power doesn't dissipate as heat like power loss through a resistor. 
>
> The question is:  What is the quantitative effect that reactive power 
> has on a battery bank that is feeding loads through an inverter?  If 
> the power factor is 56% (like a refrigerator that I want to replace) 
> does that mean that only 56% of the power being drawn from the 
> batteries is being used to power the refrigerator?.  If so, where does 
> the rest of the power go? 

If you just take your meter and multiply Volts X Amps, that's VA, or 
apparent power.   If it's all real, then it's like the resistor and gets 
counted by
the utility meter.  Some turns into heat (resistor) and some gets some 
real work done.

The rest, is VA but is Reactive and is  VA Reactive or VARs.

So, the reactive current that comes out of the batteries, into the 
inverter out the AC output, comes BACK into the battery.  (this is for 
an inverter
that has the ripple reflecting back into the battery)

So, your batter kind of discharges and then recharges 120 times per 
second for a 60 Hz system.
So, where does the power go ?   The real power gets used of course and 
most of the rest, the VARs gets put back into
the battery.   HOWEVER, since the transformer and wire and FETs and 
transormer and stuff have resistance, some of those VARS get turned
into heat by that inefficiency, or I-squared-R losses.  That's one 
reason why low power factor isn't so good.

Does that kind of make sense ?

boB

>
> Thanks,
>
> Drake Chamberlin
> Athens Electric
> OH License 44810
> CO License 3773
> NABCEP TM  Certified PV Installer
> Office - 740-448-7328
> Mobile - 740-856-9648
>
> ------------------------------------------------------------------------
>
> _______________________________________________
> List sponsored by Home Power magazine
>
> List Address: RE-wrenches at lists.re-wrenches.org
>
> Options & settings:
> http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.org
>
> List-Archive: http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.org
>
> List rules & etiquette:
> www.re-wrenches.org/etiquette.htm
>
> Check out participant bios:
> www.members.re-wrenches.org
>
>