Voltampere

hgmjr

Joined Jan 28, 2005
9,029
The wikipedia link I originally posted here was faulty. I would refer you to recca02's reply several replies ahead for a proper wikipedia link. Thanks go out to recca02 for posting a proper link.

hgmjr
 

Thread Starter

allied

Joined Mar 11, 2007
33
I plan to buy a UPS...I notice in the specification that the watts and voltampere is not the same. ( ex. 1000va , 650 watts). I call the RS component techsupport about this they not able to explain it to me they told me the will call me back to explain it but they not call me. Im just want to know the relation of watts and va on the UPS.
 

hgmjr

Joined Jan 28, 2005
9,029
The term "Watt" is most often associated with DC power consumption while the term "Volt-ampere" is most often associated with AC power consumption. The both are equivalent since they have the same units.

In AC power, the term "Volt-Ampere" is frequently used in the expression for "Apparent power" by combining it with the phase relationship between the current and the voltage. The term for "apparent power" is "volt-ampere reactive".

I would recommend that you read up the wiki article I cited and read up on the details.

hgmjr
 

Dave

Joined Nov 17, 2003
6,970
I plan to buy a UPS...I notice in the specification that the watts and voltampere is not the same. ( ex. 1000va , 650 watts). I call the RS component techsupport about this they not able to explain it to me they told me the will call me back to explain it but they not call me. Im just want to know the relation of watts and va on the UPS.
I have given you an answer over in this other thread: http://forum.allaboutcircuits.com/showthread.php?t=3986

I would recommend for clarity that we keep all further discussion on this topic in this thread. Thanks.

Dave
 

recca02

Joined Apr 2, 2007
1,214
for me the link by hgmjr didnt work probably the same for you so im reposting the link (the page contains some more links in blue colour :) try them too)
http://en.wikipedia.org/wiki/Volt-ampere

edit:consider a load of some power factor cos(phi)
then the active power is given by W = VA.cos(phi)
where VA is the apparent power(as already explained) obtained by multiplication of voltage and current at full load.
sometimes ratings are specified in terms of VA since it remains constant irrespective of load power factor as in case of transformers.
 
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