Answer / ramaraj.g

the cu loss of the transformer depends on current and iron
loss on the voltages .so total transformer loss depends on
volt- amps (VA)and NOT on phase angle between voltages and
current it is independent of the load factor. That is the
rating of transformer is in KVA /VA and NOT in KW/Watts

Answer / c_elavarasi@yahoo.com

we know,real power P=VIcos@ ,which is represented in KW.
the apparent power S=VI ,which is represented in KVA. so if
we wish to represent the rating in watt,we need the power
factor value.the power factor of the load is not known when
the transformer is manufactured,so we represent rating in
KVA as it is in no need of power factor

Answer / syed qamar abbas

There are two types of losses in transformer. One is
variable type i.e. copper loss which depends on load
current since load current is of variable nature thats why
it is called varialbe losses and the other is fixed or
constant losses i.e iron loss which depends on voltage and
frequency,since both voltage and frequency is fixed that is
why it is called constant or fixed type of losses. These
two types of losses are not affected by the power factor.
This is why transformers are rated in KVA and not KW

Answer / adeed khan

all loses in transformer depends on the current and voltage for this we can say transformer rating can measure in kw instead of KVA

Answer / vipin shishodia

As we know the load power factor is unknown for the every
transformer, we take its rating in KVA = V.I.Cos.ф. so that
whatever would be the power factor, can be taken to
calculate the load.

Answer / karthik_elec

KVA*p.f = KW, the power factor is depaending upon the load, what load we going to give we dont know, thats y transformers normaly rated in KVA, but for testing purpose we can assume p.f is 0.8 ( induction machine average p.f)

Answer / gurwinder

because the current is very high.when the current is high
then it is measured by volts.

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