Power Factor Correction (Full Lecture)
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- Опубліковано 6 вер 2024
- In this lesson we'll examine power factor correction. We'll learn that power factor correction is the addition of a variable reactive element in parallel to an electrical load, adjusted such that its reactive power is equal in magnitude yet of opposite polarity as that consumed by the electrical load. A properly power factor corrected system will deliver the same amount of real power, yet, will draw less source current. Additionally, source current will be in phase with supply voltage. (Full Lecture)
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It took me a moment to understand my forehead slapping conceptual error. I was thinking, all I had to do was match the same (inverted) reactance on both sides, but I forgot that current through each side is an integral part of the balance. That technique might work if there is no resistance on either side, but it won't work otherwise. If overall impedance on one side is lower, more current flows to that side, which increases power contribution for the side even though reactance is the same. So, you have to do the calculation the long way, balance reactive power as shown. Duh!
As usual this is another great lesson Jim. I got to spend a few years designing synchronous generators, motors, and condensers (didn't do a whole lot of those) at a company which manufactured them. We didn't really focus outside of the generator design. This is very nice to see. I look forward to the mentioned future lessons on power factor correction capacitors and synchronous condensers.
Turns out, this topic is of more than just passing interest to me, I've found. I recently installed solar panels with Enphase microinverters on each panel. I dutifully installed current sense transformers on the microinverters and connected them to my data logger. Much to my surprise, I found that the 12 microinverters draw a total of about 1 amp at night. What? How could that be? Does that mean the microinverters are sitting there dissipating 240 Vac X 1 Amp of power? Well not quite. Turns out the load is almost purely inductive. I found with an oscilloscope that the current and voltage are close to 90 degrees out of phase. Must be the microinverters employ transformers to provide standby power, and it's their inductance that is the phantom load at night. When they're connected to the City of Logan, it's no big deal because the City of Logan doesn't charge me for reactive loads. But when the reactive load is being supplied by my PowerWalls, ouch. That's not fair. Ideally, the Enphase microinverters would have built-in power factor correction but they don't. I might have to install a cut-out switch to automatically disconnect the microinverters at night or perhaps install some kind of automatic power factor correction.
Good find and great idea about the timed cut out switch. Patent this idea and sell it to Enphase!
thank you nice explanations
I tricked my lab partner into eating a capacitor and they died. Now I have to write the whole lab report on my own. luckily I have power factor correction down so this won't be too much of an issue.
Great explanation, thank you very much. Looking forward for the power generation and transmission lessons. Can you make videos about vacuum circuit breakers, sf6 breakers, electric ac generators and their voltage regulation and synchronization to external supply, other power generation related hardware? Of course if you'll have time for it. Thanks!
Eventually I'd like to do a whole playlist on power generation and transmission including HVDC and protective relaying. This is far, far in the future!
It sounds great! Thanks!
I guess the old saying we had in my Navy tech school was: ELI the ICE man follows your theory! Therefore can you say that capacitors and inductor devices exchange energy back & forth?
True dat!
Does it always (no motors involved) have to be a parallel circuit? I suppose the continuous exchange is possible in case of series connection too since S total = Sum of Si. Am I wrong?
Ordinarily the power factor correcting capacitor will be placed perfectly in parallel with whatever load impedance requires power factor correction. This being said, the load itself could be a series, a parallel, or a series-parallel combination of any number of elements. While not truly power factor correction in it's purest form you'll observe related properties in: the AC maximum power transfer theorem, resonant circuits, and voltage compensation of AC transmission lines.
thanks for the answer!