[SOLVED] Watt and VA difference

Watt is used for consumption, while VA is used for Source

Like Transformer, Generator is a source so always measure in VA.

Bulb, Fan, computer are consuming devices we use watt.


So when we will talk about rating of a consuming device, power rating unit is said to be in watts.

and when we will talk about rating of a source, power rating unit used VA.

Re: Watt and VA differencw

so what is your question? however the concept is good.

Re: Watt and VA differencw

Watt is used for consumption, while VA is used for Source

Like Transformer, Generator is a source so always measure in VA.

Bulb, Fan, computer are consuming devices we use watt.


So when we will talk about rating of a consuming device, power rating unit is said to be in watts.

and when we will talk about rating of a source, power rating unit used VA.[/QUOTE]

Not at all true. Watts is the energy consumed/produced per second. So any source or device has its rating in watts. But if the source or device is inductive in nature then ,as watts cannot be calculated correctly, the unit in which its capacity is denoted is VA. means voltamperes. which is volts multiplied by amperes. All resistive devices like incandescent bulbs, heaters etc etc are rated in watts, where as inductive devices which have coils in them are rated in voltamperes VA, like ups generators motors etc etc. hope the concept is clear.

Re: Watt and VA differencw

Just complementing what jon said:

When you have and inductive (or capacitive) source in an AC circuit, there will be a reactive factor in power. This is due to the fact that these components (inductive and capacitive) store energy from the circuit and "return" this energy peridocally to the original source. The power stored in these passive components we call Reactive Power and is followed by the unit VAR (Volt Ampere Reactive). The "real" power that disipates on the resistive partes of the circuit is measured in Watts, and the total power is measured in VA. It is actually a vector

S = (P +jQ) [VAR]

S is the total power
P is the real power
Q is the reactive power
j is the imaginary unit defined by j²=-1

Hope it helped (might have misspeled something, it's late here were I live lol).

We use watt for "power" purpose both for source and consume.
We use VA for calculating, use A for wire size and protection, and V for insulation and protection needed.