What is difference between watts and VA?

[Mikorist]

VA or volt-amps is also volts times amps, the concept however has been extended to AC power.

For DC current:

VA = Watts (DC current).

In AC if the volts and amps are in phase (for example at a resistive load) then the equation is also:

VA=Watts (resistive load)

where V is the RMS voltage and A is the RMS amperage.

The Difference between Watts and VA is called the 'Power-Factor'.Multiply the VA by the P.F. and you have Watts. If the Voltage andcurrent are 'out of phase', not all of the power is converted to usefulpower in an AC system.

As an analogy: Imagine a ferry want tocross a still river. It powers directly across from point A to B. Allof it's power is used in getting directly across (e.g. a DC system)

Now imagine the river is fast flowing. the captain needs to point theferry upstream and drive against the current, which will push himbackwards in an arc towards point B on the opposite side. He used morepower, but still only got to point B.

The result of getting fromA to B is the equivalent to Watts. The energy generated and usedgetting from A to B in the fast river is VA. Watts / VA is the factorof the power used, or power-factor.

Power companies have togenerate power in VA. You only pay for Watts used, so there's a lot ofpower lost in the lines and transformers in trying to overcome a poor

'power-factor'.

power-factor:

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/powfac.html