Talk:AC power

message: Looking carefully you will see that the sign reversal of the product of V and I occurs every quarter cycle, not every half cycle.  I had to draw it out because the 90 degrees does not allow for that to occur for a half cycle and it choked my senses, so I drew it out. Yes, I know that adds up to a half cycle per cycle, but when getting down to that level it is obvious that the sign of V and I are opposite on alternate quarter cycles.... 
Regards,  -- Steve --  (talk) 01:23, 16 January 2017 (UTC)
thread_title:  Reactive Power 

message: Right now, the merges suggested look like this (i think):
: Electric reactance -> AC power -> Alternating current
I'm okay with this, except may I suggest that we first merge Electric reactance -> Reactance, so that the mergers would look like this:
: Electric reactance -> Reactance -> AC power -> Alternating current
Reactance appears to this layman as the better written article. The only reason for merging Reactance -> Electric reactance, is to distinguish this from the sense in which Reactance is used in chemistry.  Just a thought. Vonkje 11:51, 3 October 2005 (UTC)
thread_title:  Proposed mergers 

message: This is a very nice article, but a bit more than I need to know.  I'm trying to understand, something more basic, the difference between Watts and Volt-amps in the real world.  I have a meter that measures both watts and VA when you plug in normal household appliances.  If I plug in an incandescant bulb the watts and VA are virtually identical, if it is a compact flourescant bulb the VA are almost twice the watts.  I understand why this is, but my question is more basic.  Which is being measured by my electric meter?  I'm under the impression that it counts VA hours but calls them watts.  If this is so, why do all electric appliances come rated in watts and not VA? -- Samuel Wantman 06:35, 18 January 2006 (UTC)
replies: text: I think at least here in the uk domestic meters do actually measure watts (meters for large commercial and industrial installs measure watts and VArs seperately). but i'm not entirely positive. Plugwash 14:16, 18 January 2006 (UTC)

text: VA hours would not be equivalent to watts.  It's equivalent to joules.  The difference between VA and W is real vs apparent power, as explained in the article. — Omegatron 17:20, 18 January 2006 (UTC)
thread_title:  Watts, volt-amps, and power meters 

message: Reactive Power carries much more significance than what is highlighted in this article. I think that Reactive Power should not be combined with AC Power. A few major points about Reactive Power not discussed here, are:
 Reactive Power - Power System Voltage regulation (Voltage Control)
 Significance of Reactive Power in Power Industry today
 Efforts on part of Regulatory/Governing bodies to ensure availability of reactive power for System Stability
 Compensation of Electric Generators for providing Reactive Power in emergency situations
Other discussions will come up as soon as we open this topic. Therefore, I request you to create a separate topic for Reactive Power.
:It certainly deserves mention in a general article on AC power but there is no reason there cannot be a seperate article on it if you belive you can produce enough content for one. Plugwash 21:25, 17 November 2006 (UTC)
thread_title:  Reactive Power 

message: Could someone talk about the resolution that came about in the 1990s? That is an interesting story and should be further discussed in this article, or a link should be provided if it is discussed elsewhere.  —Preceding unsigned comment added by 131.183.23.25 (talk) 15:39, 4 September 2009 (UTC)
thread_title:  Unbalanced Polyphase Systems 

message: I've read the article and all the comments on this talk page and everything / everyone seems to be describing a full sinusoidal wave form but what about North America where 220-240vac sine wave gets split into two 110-120vac half sine waves?
for examle the picture of the blinking light trace describes 2 blinks per wave whereas in north america if the light was connected to 110-120 ac wouldn't there be just 1 blink per wave?
in general, I've been finding wiki articles regarding mains power lacking not adequately describing (or ignoring) North American household use of AC
I'm not an effective writer so I'm not qualified to offer anything more than a suggestion or a request that someone modify these articles to include single phase half-wave power usage :-)  — Preceding unsigned comment added by 24.6.92.12 (talk) 05:49, 25 February 2012 (UTC)
replies: text: <months later> Have a look at Split-phase electric power. It's not "two half sine waves". --Wtshymanski (talk) 13:29, 15 May 2012 (UTC)
thread_title:  am I going to open a can of worms? 

message: «This method of calculating the average power gives the real power regardless of harmonic content of the waveform. In practical applications, this would be done in the digital domain, where the calculation becomes trivial when compared to the use of rms and phase to determine real power.
 P_{avg} = \frac{1}{T} * \sum_{k=1}^n  v[k]*i[k] »
Shouldn't it be:  P_{avg} = \frac{1}{n} * \sum_{k=1}^n  v[k]*i[k]  ?
89.181.225.20 (talk) 01:11, 15 May 2012 (UTC)
thread_title:  Average power 

message: The diagram is nice, but WHAT is the formula, or a precise definition of complex power? It is not stated anywhere in the article... --82.54.173.32 (talk) 20:53, 6 June 2012 (UTC)
replies: text: Complex power is defined ("defined" means you can't prove it from any other equation or theorem) as one half the voltage phasor times the complex conjugate of the current phasor, or, as the RMS voltage phasor times the complex conjugate of RMS current phasor. Why? Because this leads to a very useful quantity: its real part is the average or active power, its imaginary part is the reactive power, its magnitude is the apparent power, and it's angle is the power factor angle.-- Alej27 (talk) 04:40, 21 October 2020 (UTC)
thread_title:  Complex power 

message: In the contents navigator, clicking on "Reactive power" leads to "1 Active, reactive, and apparent power". Shouldn't it lead to "3 Reactive power"? 129.247.247.238 (talk) 10:27, 18 February 2015 (UTC)
thread_title:  Wrong HTML Anchor 

message: I have edited the reactive power section to clarify the differences between inductive loads and capacitive loads and their effects on reactive power and power factor. Some statements were made in the form of "this causes the voltage to lag the current" and I changed them to reflect the convention that voltage is defined as 0 degrees. I also added more information about sourcing vs. sinking reactive power and added the fact that inductive loads are primarily made up of generators and motors. A more in depth discussion about why reactive power is useful or necessary for power system operation. 
Regarding the reactive power control section, I looked around and couldn't find the formula that was referenced. Also the phrase "pre-fault reactive generator use" is confusing, and I'm not sure what it means. 
A figure illustrating the relationship between complex power and voltage and current and their shared angle would also be illustrative and useful.  — Preceding unsigned comment added by Tripleripple (talk • contribs) 07:30, 29 April 2015 (UTC)
thread_title:  Reorganization of Reactive Power Section 

message: It says, "This voltage increases until some maximum dictated by the capacitor structure."  There are other things that also affect the maximum voltage a capacitor will charge up to, such as other circuit elements, so the point of that sentence isn't clear, not in context or otherwise.  I think the explanation of the current leading in a capacitor might be more concise if that sentence were simply eliminated.  I might put more emphasis on the voltage of a capacitor being unable to change instantaneously (with an explanation of why can't it -- in the cases of increasing or decreasing applied voltage), thereby causing a phase lag in the voltage relative to current when the applied voltage changes, i.e. voltage-lagging in the capacitor (or current leading).75.110.98.103 (talk) 15:52, 10 March 2016 (UTC)
replies: text: I agree with you. Since the current through an inductor can't change abruptly but voltage can, current lags voltage here. Since the voltage across a capacitor can't change abruply but current can, voltage lags current (or also current leads voltage) here. This is the explanation of the phrase ELI the ICE man. --Alej27 (talk) 04:48, 21 October 2020 (UTC)
thread_title:  Section: Capacitive vs. Reactive Loads 

message: Please explain asterisk in formula. 
—DIV (120.17.54.174 (talk) 12:33, 5 August 2018 (UTC)
thread_title:  Asterisk 

message: The term "power" has a lot of meanings. If we're talking about transformers, it usually means the apparent power. If we're talking about motors, it usually means the output mechanical power. If we're talking about a load, it usually means the active power (also known as average power or real power.) If we're talking about a capacitor bank, it usually means the reactive power.
So, as you can see saying "power" alone might be misleading. Because of this, I suggest to change in the very first paragraph of this article, the word "power" for "instantaneous power", which is what whoever wrote it meant (the rate of transfer of energy or the rate of work being done.) --Alej27 (talk) 01:21, 21 October 2020 (UTC)
thread_title:  Is it okay for you if in the first paragraph I change "power" to "instantaneous power"? 

message: In that section, it reads "While active power and reactive power are well defined in any system, the definition of apparent power for unbalanced polyphase systems is considered to be one of the most controversial topics in power engineering." Why is it controversial? In a two-terminal (i.e. single-phase) element/device/load/generator, apparent power is defined as the product of RMS voltage times RMS current. This definition applies whether in sinusoidal steady-state (no harmonics) or in non-sinusoidal steady-state (with harmonics), and whether in balanced or unbalanced systems.
In balanced three-phase systems, the previous definition is usually called single-phase apparent power or per-phase apparent power, while the three-phase apparent power or total apparent power is three times the previous quantity.
In unbalanced three-phase systems, the single-phase apparent power is still RMS voltage times RMS current.
Maybe the controversy the section talks about is regarding three-phase (and not single-phase) apparent power in unbalanced three-phase systems? Can someone clarify me this? If that's true, then my point of view is that people/engineers can't expect apparent power to be the sum of the single-phase apparent power of each leg of the device, not because the system is unbalanced, but because the apparent power is not a conserved quantity (unlike active/real power, reactive/quadrature power, and complex power). --Alej27 (talk) 01:03, 31 October 2020 (UTC)
thread_title:  What's the point of the section "Unbalanced polyphase systems"? 

message: The user Wtshymanski recently changed an example in the Power factor section of the article, to the following sentence:
: "For instance, a power factor of 0.68 means that only 68 percent of the total current supplied (in magnitude) is actually doing work; the remaining 32% does no work."
I think it's misleading the phrase "the remaining 32% does no work". What does that 32% represent? Please clarify. As far as I know, there's no other 32%, because the relation between active current and reactive current is orthogonal, meaning I_\text{rms} = \sqrt{I_\text{rms,a}^2 + I_\text{rms,r}^2}, thus the reactive current is sin(arccos(0.68)) ≈ 0.73 = 73% the total current, not 32%, as shown in the following figure for a RL load.
So, I think we should remove the phrase "the remaining 32% does no work". Or we could be more specific in the example, and instead say something like:
: "For instance, in sinusoidal steady-state, a single-phase load with a power factor of 0.68 means that the RMS value of the active component of the total current (the one corresponding to the active power or net energy transfer) is just 68% of the RMS value of the total current".
or in fewer words:
: "For instance, a single-phase load with a power factor of 0.68 means that the active current (the one corresponding to the active power or net energy transfer) is just 68% of the total current".
And if we want to talk about the remaining current, we could talk about the reactive current, adding the following to the previous sentence:
: "On the other hand, reactive current (the one corresponding to the reactive power or no net energy transfer) is 73% of the total current."
What are your thoughts? --Alej27 (talk) 20:45, 12 August 2021 (UTC)
thread_title:  Clarify power factor example