Answer / s hubertsubis

There are two losses in transformer cu loss depends on
current & iron loss depends on voltage total loss depends
on voltamper(VA)at that time we do not require power factor
thats way we mentioned transformer rating in kva not in kw

Answer / shyamkr

because at that time we don't know load of which power
factor is we r going to use.....
so we keep the rating of transformer in kva and not in kw...

Answer / naveen

kVA is the unit for apparent power. Apparent power consists
of active and reactive power. Active power is the share of
the apparent power which transmits energy from the source
(generator) to the user. Reactive power is the share of the
apparent power which represents a useless oscillation of
energy from the source to the user and back again. It occurs
when on account of some »inertia« in the system there is a
phase shift between voltage and current. This means that the
current does not change polarity synchronous with the
voltage. But the heat generated in a winding as well as the
eddy current losses generated in a transformer core depend
on the current only, regardless of whether it aligns with
the voltage or not. Therefore the heat is always
proportional to the square of the current amplitude,
irrespective of the phase angle (the shift between voltage
and current). So a transformer has to be rated (and
selected) by apparent power.

Answer / umesh yadav

POWER GENERATING DEVICE LIKE AS tRANSFORMER, DG SETS ARE
RATED IN kva BECAUSE WE DONT KNOW ABOUT THE LOAD THAT IT IS
acTIVE OR REACTIVE, SO TO SUPLLY THE DIFFERENT LOAD WE
RATED TRANSFORMER AND DG SETS IN kva.

Answer / pawan

because power factor do not fix.so have transformer and DG
Ratingin kva

Answer / tony

Transformer load depends on Voltage and current not on power factor or phase angle between voltage and current so it is rated in VA .So we used KVA ; total power for a transformer can supply.

Answer / santosh kawade

Transformer is a passive device hence rating of transformer
is always mentioned in KVA.

Transformer itself is not a end user of electrical power
(it do not consume power), it is only media of tramitting
voltage levels.

Power factor at transformer terminals (primary or
secondary) is depends on power factor of loads connected at
lower end, hence rating of transformer alway mentioned in
KVA.

santosh kawade
9224 69 3116

Answer / pawan dahiya

Transformer Load do not Fix because depand in load ,So not
fix load area(system) used KVA and fix load area use KW

Answer / karthikeyan

we consider power factor is unity for transformer
so rating is kva

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