Answer / saranraj

Transformer Both the losses of the transformer is
independent of the
power factor (cos phi), which means a transformer would not
make any change in the power factor, since both the losses
viz copper loss(depends on current) and iron loss(depends
on voltage) are independent of power factor, that is why a
Transformers rating is not on kW, but on KVA

because,ironloss is depends in voltage and cu_loss is
depends in current.so the transformer ratings in kva

Answer / girish kumar samal, hindalco,h

actually rating of a equipment depends upon heat , which
depends upon loss. as in transformer both copper loss &iron
loss dont depend upon power factor . so transformer rating
is in kva.

Answer / guest

ironloss depends on voltage and cu_loss
depends current.so the transformer ratings is in kva

Answer / love007

iron loss depend upon vtg & cu loss depend upon current
it threrotical also
we don't know load is pure resitive or inductive
so Xmer rating in KVA
b'coz in res load KW=KVA, inductive KVA=KW/COSpi

Answer / mahamuni raja

copper losses of a transformer depends on CURRENT and irons
of a transformer depends on VOLTAGE not an phase angle
between voltage and current. that is why transformer rating
in KVA not an KW.

Answer / asfaq

Transformer has two types of losses and they are iron loss &
copper loss.Iron loss depend on voltage while copper loss
depend current,also power factor is independent of both
losses.so rating is in KVA.one more reason is that we dont
know which type of load is connected to transformer.
Power=Voltage*Current*Powerfactor
Power factor is different for different typrd of load
so rating is KVA as per my knowledge

Answer / vijay saharan

the cu losses rating in curent and iron losses rating in
voltage so the both losses are trnsformer and this is the
cause trasformer rating in kva.

Answer / suresh

kVA is the unit for apparent power. Apparent power consists
of reactive and active 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 / ravi r estake

Because losses of transformer is dependent on current &
voltage probably copper & core losses.

Answer / amr mobarak

so For Active Power the Equation will be

P (primary) = P (secondary ) + P cu Losses + P iron Losses

Which can't describe our transformer with certain value in
both primary & secondary

why designer use kva rating instead of kw in transformer rating???????????????

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