Answer / sam

It might be better in the future to ask electrical questions
in the electrical section, rather that trying to find
someone in instrumentation that can give you answers on
electrical problems you are struggling to understand.

Here's what you need anyway,

Since watts is volts times amps, what is VA?
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 a
resistive load) then the equation is also:
VA = Watts (resistive load)

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

In AC the volts and amps are not always in phase (meaning
that the peak of the voltage curve is does not happen at the
peak of the current curve). So in AC, if the volts and amps
are not precisely in phase you have to calculate the watts
by multiplying the volts times the amps at each moment in
time and take the average over time.

The ratio between the VA (i.e. rms volts time rms amps) and
Watts is called the power factor PF.

VA•PF = Watts (any load, including inductive loads)
In other words, volt-amps x power factor = watts.
Similarly, KVA*PF = KW,
Or kilovolt-amps times power factor equals kilowatts.

When you want to know how much the electricity is costing
you, you use watts. When you are specifying equipment loads,
fuses, and wiring sizes you use the VA, or the rms voltage
and rms amperage. This is because VA considers the peak of
both current and voltage, without taking into account if
they happen at the same time or not.

Finding the Power Factor:
How do you find the power factor? This isn’t easy. For
computer power supplies and other supplies that are power
factor corrected, the power factor is usually over 90%. For
high power motors under heavy load the power factor can be
as low as 35%. Industry standard rule-of-thumb is that you
plan for a power factor of 60%, which somebody came up with
as a kind of average power factor.

Converting VA to Amps:
How to convert VA to amps? Use the following formula:
A = (VA*PF)/V
Where A stands for the RMS amps, VA stands for volt-amps, V
stands for RMS volts and PF stands for the power factor.

Converting VA to Volts
How to convert VA to volts? Use the following formula:
V = (VA*PF)/A
Where V stands for RMS volts, A stands for the RMS amps, VA
stands for volt-amps, and PF stands for the power factor.

What is KVA?
KVA is just kilovolt-amps, or volts times amps divided by 1000:
KVA•PF = KW (any load, including inductive loads)
Where KVA stands for kilovolt-amps, KW stands for kilowatts,
and PF stands for the power factor.

Keep the factor of 1000 straight when dealing with mixed units:
KVA•PF = W/1000 (any load, including inductive loads)
VA•PF = 1000•KW (Kilowatts to VA)

The Following equations can be used to convert between amps,
volts, and VA.

Converting VA to Amps (voltage fixed)
The conversion of VA to Amps is governed by the equation:
Amps = VA•PF/Volts)
For example 12 VA•0.6/(12 volts) = 0.6 amp

Converting KVA to KW (Kilovolt-amps to Kilowatts)
The conversion of KVA to KW is governed by the equation:
KVA = KW/PF)
For example, if the power factor is 0.6
120 KVA•0.6 = 72 Kilowatts

Converting Watts to KVA (watts to kilovolt-amps)
The conversion of W to KVA is governed by the equation:
KVA=W/(1000*PF)
For example 1500W/(1000*0.83) = 1.8 kVA (assuming a power
factor of 0.83)

Converting Amps to VA (voltage fixed)
The conversion of Amps to VA is governed by the equation:
VA = Amps • Volts/PF
For example 1 amp * 110 volts/0.6 = 183 VA

Converting Amps to KVA (voltage fixed)
The conversion of Amps to KVA is governed by the equation:
KVA = Amps • Volts/(1000•PF)
For example 100 amp * 110 volts/(1000*0.6) = 18.3 KVA

Converting VA to Volts (current fixed)
The conversion of VA to Volts is governed by the equation:
Volts = VA•PF/Amps
For example 100 VA • 0.6/10 amps = 6 volts

Converting Volts to VA (current fixed)
The conversion of Volts to VA is governed by the equation:
VA = Amps • Volts/PF
For example 1.5 amps * 12 volts/0.6 = 30 VA

Converting Volts to Amps at fixed VA
The conversion of Volts to Amps is governed by the equation:
Amps = VA•PF/Volts
For example 120 VA* 0.6 /110 volts = 0.65 amps

Converting Amps to Volts at fixed VA
The conversion of Amps to Volts is governed by the equation:
Volts = VA•PF/Amps
For Example, 48 VA • 0.6 / 12 Amps = 2.4 Volts

Explanation
Amps are how many electrons flow past a certain point per
second. Volts is a measure of how much force that each
electron is under. Think of water in a hose. A gallon a
minute (think amps) just dribbles out if it is under low
pressure (think voltage). But if you restrict the end of the
hose, letting the pressure build up, the water can have more
power (like watts), even though it is still only one gallon
a minute. In fact the power can grow enormous as the
pressure builds, to the point that a water knife can cut a
sheet of glass. In the same manner as the voltage is
increased a small amount of current can turn into a lot of
watts.
Good luck and ask the electricians these questions in the
future please.

Answer / pankaj dubey

as we all known that p.f= kw/kva

then kw= kva*p.f. or kw = vicos@ where kva = vi

and p.f. = cos@

Answer / sam

This is really a basic electrical question but anyway,

Power is measured in Watts and the symbol for power is "P"
and for watts "W"

The formula to calculate Power is Volts X Amps

So this can also be written in short as P = V X A

Since as you have learned in basic mathematics that if there
is no sign between two symbols that means multiply,
so the above can also be written as P = VA and the answer
will be in Watts.

The electrical people have different ways to refer to Power
but it is all exactly the same thing.

They could either call it 1250KVA or say it out fully like
1250KiloWatts(KW), since as above VA = W.

KVA = Kilo (Volts X Amps) = Kilo (Watts)

also

1000Watts = 1 Kilo Watt

Good luck

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