Talk:Volt-ampere

message: I just about understand the difference between a Watt and a Volt Amp.  What I am curious about, is is whether a normal domestic electricity meter measures Watt hours or Volt Amp hours.  I am finding, in some cases, a factor of six difference between the two statistics on some appliances.
:The standard household electrical meter presently measures kWh (energy in kilowatthours) although some of the more advanced meters can also record other quantities such as kilovarhours, peak kVA demand, demand interval data, etc. Industrial and commercial facilities are often billed on VA demand in addtion to kWh. Nearly all households today are billed solely on kWh.
Rcdugan 17:42, 23 June 2007 (UTC)
replies: text: By design, watthour meters integrate true power, that is, watts. (That is, the integral of power in watts with respect to time.)  Connecting an ideal inductor or ideal capacitor should integrate zero watts.  But it is possible that, due to nonlinearities, that the measurement isn't perfect. But note that reactive power has a cost to the power company, as it increases the current, and so ohmic loss in power lines.  Also, it requires larger wire and larger transformers. Gah4 (talk) 08:26, 11 January 2017 (UTC)
thread_title:  Standard watthour meter 

message: The section about 70% and the example formulas appear to be a response to some specific question that has been left out.  These formula would only apply to a device with a known power factor of .7.  This section should be removed and probably just replaced with a reference to the article on Power Factor.
Nevermind, someone seems to already be fixing it.
D3z (talk) 04:50, 17 June 2008 (UTC)
replies: text: The 70% is not due to power factor. It is because VA is based on peak values, and Watts is RMS. Madkaugh (talk) 00:30, 16 October 2009 (UTC)
replies: text: VA is normally based on RMS current and RMS voltage. Other than as described by the US FTC, power (watts) are never RMS. Gah4 (talk) 11:45, 11 January 2017 (UTC)
thread_title:  Why 70% 

message: The vast majority of Wikipedia articles are very useful, and contain a minimum of errors.
Sadly, the above doesn't apply to the Volt-ampere article. It is wrong in most respects, and what remains is misleading. The article should be removed entirely.
VA is simply what it implies - RMS Voltage multiplied by RMS current. The waveform is immaterial, so any reference to 0.7 (which implies a sinewave) is irrelevant and grossly misleading. VA is commonly referred to as "apparent power", but this is not a physical property per se - Volts, Amps and Power are physical properties (in that they are defined quantities in physics textbooks).
"Volt-Amps" (VA) is simply a useful quantity in electrical engineering, and in most cases is far more useful than Watts because the power factor of the connected loads is often an unknown quantity. VA and Watts are only equivalent where the load has a unity power factor (i.e. is essentially resistive).
Rode sound (talk) 02:45, 21 October 2009 (UTC)
thread_title:  Volt-ampere corrections 

message: Please provide some details and examples of conversions and relation to better known units, esp. WATTS. I came here not recalling what a Volt-Amp or VA equals, though I hobby with electricals and electronics bits occasionally. I just don't see VA ratings that often to worry. 
Clarity: I find some of the Wiki text confusing, more so now that I read the "talk" page. At this site: http://www.supercircuits.com/resources/tools/Volts-Watts-Amps-Converter they think that a VA directly equals a watt. Wiki should explain if this relationship is true or not, why and under what circumstances, and in language not requiring a EE (though it would be best to accommodate both levels of expertise). Here's a site which does a good job of that and I hope Wiki will model part of the article on it: http://www.power-solutions.com/watts-va.php . For the real techies (and I am at times), this is a great help: http://www.powerstream.com/VA-Watts.htm Jopower (talk) 23:15, 1 June 2012 (UTC)
replies: text: As far as I know, VA is mostly used in rating transformers. Maybe also motors, but less often. For a motor, the current rating tells the size of wire and switches needed, and also for any transformers used. It is especially convenient for transformers, since it works in either direction. It also tells the size of wire and switches needed for the other side of a transformer. Gah4 (talk) 10:57, 8 December 2019 (UTC)
thread_title: Conversion examples and article clarity

message: The article seems to suggest that VA only applies when the current and voltage are sinusoidal.  I believe that this isn't true.  VA is the product of RMS voltage and RMS current, independent of the wave shape. Among others, it allows one to find the current in a wire, knowing the voltage and VA, which is necessary to determine the wire size. Non-linear loads, such as HID lamps, generate a large third harmonic in the current. This adds complication in three phase systems, more than just VA tells you. For even more non-linear loads, such as many switching power supplies, peak current could be high, while RMS isn't so high. Again, VA isn't all you need to know. Gah4 (talk) 07:34, 4 November 2017 (UTC)
replies: text: I was about to write this, but then I find that I already did. The mention of sinusoids of the same frequency is still there. One common case is the third harmonic (maybe more) with non-linear loads, such as discharge lamps. So you can have a third harmonic current, and first harmonic voltage determining VA. Gah4 (talk) 10:59, 8 December 2019 (UTC)
thread_title:  sinusoidal 

message: Someone removed the statement: SI allows one to specify units to indicate commosn-sense physical considerations.  The reason for that, was that previously someone claimed that SI didn't allow such units.  I am not against the removal, but I don't understand the edit summary about a how to guide.  Is it obviously an allowed SI unit now? Why does that statement make Wikipedia a how to guide? Gah4 (talk) 06:32, 3 December 2017 (UTC)
thread_title:  How to? 

message: VA = Watts divided by power factor.
2600:1700:4CA1:3C80:F037:D0E9:72E7:94FE (talk) 00:53, 16 April 2018 (UTC)
thread_title:  How did you not put this in? 

message: I believe I put: SI allows one to specify units to indicate "common sense physical considerations" in many years ago, along with an appropriate reference, replacing a statement that said the exact opposite. If there are no questions about it, I am fine with removing it. Gah4 (talk) 06:48, 27 August 2023 (UTC)
thread_title:  SI allows one to specify units to indicate ''common sense physical considerations''