I have found that many inverters will have a poor power factor when producing low power, and the power factor improves with load. if there are other things on your load it can effect the power factor./ I have also seen very low power factor when motors run unloaded. I remember a gas dryer with no clothes and the power factor was 0.24
Power Factor is like a spring, a piece of equipment will draw current like compressing a spring and then send it back, so the utility has current flowing in the wires but no net work or no kWh DT ________________________________ From: "[email protected]" <[email protected]> To: RE-wrenches <[email protected]> Sent: Monday, May 7, 2012 11:47 PM Subject: Re: [RE-wrenches] power factor excellent replies to yes, a complicated issue. i think i finally understand this. thank you kent and dan! todd On Monday, May 7, 2012 9:02pm, "Exeltech" <[email protected]> said: Hello Todd, The short answer to your "is this a concern?" query, is "no". Reactive power is one of the more complex aspects of electric power, and certainly one of the most misunderstood. It can and does involve inductive loads (e.g. motors), capacitive loads (e.g. some types of power supplies), and non-linear loads (e.g. switch-mode power supplies, dimmers, etc.). You likely know (or should know) "power factor" is the ratio of real power to reactive power consumed by a load. Grid-tie inverters generate "real" watts, which are then coupled to the grid. When a reactive load in your home is consuming power, and you provide real watts to the load from the inverter, this changes the ratio of real to apparent power consumed by the load as seen by the utility company. Dividing real power by apparent power results in a unit-less value between 0 and 1 that describes this ratio. Let's say a load in your home is consuming 1,200 real watts, and 1,250 apparent watts. This results in a power factor of 1200/1250, which equals 0.96. Pretty darn good. Next, your grid-tie inverter provides 1,000 real watts back to the utility company, which in turn is 1,000 real watts that the utility company no longer needs to provide to the load described above. Thus the net "real" power consumed as seen by the utility is now 1,200W - 1,000W = 200W. This means they sell only 200 watts to power your load, but the "apparent" power aspect is still there. End result? 200 real watts / 1250 apparent watts yields a power factor of 0.160. Terrible by any power company standards, yet you've removed 1,000 watts from the grid. This is the value that will be displayed on your meter. Efforts are underway by EPRI and others to help create standards for future generations of grid-tied inverters capable of generating "reactive" power (where volts and amps are out of phase with each other) to help mitigate this effect. I'm a member of the committee working toward that goal. (No, we're not there yet. It'll take time.) This is a very difficult topic to discuss and explain. Hopefully this helped. Like Tom Cruise said at the end of "Top Gun" .. "It's complicated." Dan --- On Mon, 5/7/12, [email protected] <[email protected]> wrote: >From: [email protected] <[email protected]> >Subject: [RE-wrenches] power factor >To: "RE-wrenches" <[email protected]> >Date: Monday, May 7, 2012, 9:46 PM > > >wrenches, > >> >i have a question about my home's system. i was one of the first net metered >systems in our area, so the utility company installed a fancy dual register >meter which also displays kvar/power factor. > >> >when selling 1 kW today the power factor was .40 and the kvar was 2.37. > >> >this sounds horrible. question: is this a concern? > >> >todd > >> > >> Sent from Finest Planet WebMail. >-----Inline Attachment Follows----- > > >_______________________________________________List sponsored by Home Power >magazineList Address: [email protected] & >settings:http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.orgList-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.orgList rules >& etiquette:www.re-wrenches.org/etiquette.htmCheck out participant >bios:www.members.re-wrenches.org Sent from Finest Planet >WebMail._______________________________________________List sponsored by Home >Power magazineList Address: [email protected] & >settings:http://lists.re-wrenches.org/options.cgi/re-wrenches-re-wrenches.orgList-Archive: > http://lists.re-wrenches.org/pipermail/re-wrenches-re-wrenches.orgList rules >& etiquette:www.re-wrenches.org/etiquette.htmCheck out participant >bios:www.members.re-wrenches.org
_______________________________________________ List sponsored by Home Power magazine List Address: [email protected] 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
