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MSEE, PE -
Cheers!!
I have to disagree with you SK, just because many of the contributors on this site have little electrical knowledge it doesn't mean we have ZERO knowledge of algebra or mathematics in general. I have to say that since joining this very interesting site I have learned a huge amount, I am taking an online course in Basic concepts in Electricity, I have modified and greatly improved my off-grid setup in my shed and I have a new interest in life now. I can safely say now, that I know and understand the meaning of many of the electrical terms that you commonly use, however when reading this page I realize there is a huge amount that I do not know but that only inspires me to study more (I do have plenty of spare time these days). I thank all of you gurus for your undying patience with us DIY'ers!Comment
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PF
I am not at that stage of learning yet and perhaps never will be. All I know are the basic formulas for power such as P = IE or P = I(squared) R and Ohm's law E = IR. I am adding to this knowledge daily however.
As I said I am a new to this and perhaps I will take some time to get to an intermediate level of knowledge which will probably be where I peak in this particular field of study. I know my own capabilities and where my strengths lay.
My main hobbies are gardening and racing Go-karts, perhaps I know enough about them to teach some of you electrical guys a thing or two!!
Is knowing PF critical for me at this point or useful for me to understand?Comment
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It's not that critical. Devices that have big motors in them sometimes have a poor power factor and need bigger inverters to operate. Small wall warts (laptops, cellphone chargers etc) can also have poor power factors, but they are generally smaller loads so the poor power factor matters less. Overall if you just allow some margin for power factor you are generally OK.
The two areas that you might look into if you want to learn more about power factor are peak rectification and complex impedance. Peak rectification refers to devices that only take power during a small part of the AC waverorm (requiring an inverter that provides a higher peak power) and complex impedance describes loads whose current waveform is not completely in sync with the voltage waveform. Both are more difficult for an inverter to drive, but modern inverters are designed with non-ideal loads in mind.Comment
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Power factor (PF) is one of those measurements that have no effect on 99.9% of people. Most people buy a AC or refrigerator or microwave oven without ever needing to know their PF.
Grid power can cope with just about every residence having some devices with far from perfect PF.
Its only a concern to the following electrical engineers designing big industrial factories and similar, power companies charging those factories,and when you are into using off grid solar power for your residence.
To most of the people that need to get PF as close to 1 as possible are off grid solar power users. The reasons being that "bad" PF wastes your battery/ies power. Less run time from any given battery capacity.
If the old standard of assuming PF of .8 then you wont go far wrong in estimating your battery power usage.
PF is really one of those measurements like Lumens ..If your room is not bright enough you dont go checking the Lumens ,you just go upgrade your existing 60w lamp for a 100w one...You get the idea.Comment
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A bad or low Power Factor is no good for either the utility or the homeowner. Utilities charge a PF penalty to customers to help them reduce waste on their distribution system.
While a residential connection does not usually have a PF penalty added to their bill by the Utility, a low PF means they have losses in their electrical system. These losses will use up some of the total available kva of their transformer capacity in their inverter.Comment
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PF is no ta huge problem for TSW inverters, but can be a major problem for MSW inverters. However even TSW inverters can have a problem for example running a lot on non linear loads like switching power supplies found in Desktop computers and cheap CFL light bulbs where PF can be .6 or even less. Most TSW inverters can only handle .8 PF at full power.MSEE, PEComment
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Sunking. Thanks. I didn't know about the difference between a TSW and MSW inverter.
You are also correct about the non linear switching loads. They cause harmonics which increases both Voltage and Current distortion which can cause bigger losses than a low PF.
Actually that is my job to help our customers eliminate these harmonics by installing HMI type transformers. By putting in transformers with higher efficiencies that also mitigates the triplet harmonics there is a good change of reducing their electric bills by 4 to 6% as well as eliminate issues caused by the harmonics.Comment
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Playing with words? Where on the residential bill does it specify a penalty for poor power factor? What utility anywhere around points out a charge to the residential customer a penalty for poor power factor? None that I know of. Of course the end customer always pays.
For commercial use it is standard to have a penalty clearly charged.[SIGPIC][/SIGPIC]Comment
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The only way a residential customer would end up paying more for a high PF is if the utility-supplied meter reads incorrectly in the presence of higher harmonics in the current waveform. And as far as I know, none do, but I am open to a counterexample.
A commercial meter can be configured to record either average or worst case PF in addition to recording the real power (watts) consumed.SunnyBoy 3000 US, 18 BP Solar 175B panels.Comment
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Not playing with words. Just not trying to be too definitive by saying no residential bill has a power factor penalty added to it. Since I do not have direct knowledge of all resident tariffs I felt if there were any at all then by saying most do not I was being as truthful as possible.
You are also correct when you say the customer always pays one way or the other. Utilities will find a way to pass on the costs to all customers.Comment
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Which unfortunately gives the individual homeowner no economic incentive to reduce their PF.
BTW, since the problems an inverter has with low PF loads are most noticeable near full rated output, the thing you have to watch is the PF of your largest (usually motor) loads. If the only thing you are powering is CFLs and computer power supplies, you are probably nowhere near the full output of your inverter unless that is the entire load that you have planned for.SunnyBoy 3000 US, 18 BP Solar 175B panels.Comment
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