Answer / munna

because,ironloss is depends in voltage and cu_loss is
depends in current.so total loss depend on VA.so the transformer ratings in kva.


Reference : B.L Thereja - AC/DC machine

Answer / karan lal

ironloss is depends in voltage and copper loss is
depends in current.so the transformer ratings in kva

Answer / nagaj jvk

the transformer just transfers the power but does nt depend onthe phase angle between the voltage and current ie it is independent of the load power factor....and more over the losses of the transformer - core losses depends on voltage and
copper losses depend on current and there is nothing to do with power factor and thus it is the apparent power that makes
pf not to come into picture and thus it is rated in kva

Answer / saeid

Generally speaking Watt is unite of work in physics.
Anything that does some work, on of its specification is
KW . So KW is used for whatever equipment or machine that
does work. Generator, motor, heater or a lump do work and
they are identifying by KW. However, a transformer doesn't
do any work. It only transfers electrical energy. It’s not
considered a source of power or a load for power system. As
a result, we use KVA to identify capacity of a transformer
instead of KW.
Additionally, I do not believe that this discussion is
related to power factor, copper loss or core loss of the
transformer.

Answer / amarjeet kumar

Transformer have basically two types of losses one is copper loss and other is core loss, and copper loss depends upon current, and core loss depends on voltage so it rating is measured in multiple of current and voltage i.e in KVA.It is independent of power factor. Thats why its unit is not in KW.

Answer / ravi babu p

The performance of the transformer is estimated in terms of
efficiency and the efficiency is influenced by the losses,
i.e. core and copper losses. Core losses are depends on the
magnitude of voltage(V) and No-load current(A) (very small
in magnitude), where copper losses depends on the full load
current(A). Hence, the transformer is rated in kVA.

Answer / harit thaker

because transformer depend on the load and we do not know the load which is either inductive or capacitive. when the load connected with transformer so the power factor always reduce so that time reactive power taking action so losses is increase but we maintain the power factor nearly 0.98 to unity at that time only getting active power when power factor reduces the reactive power taking action that time active power become low according to power triangular so that transformer rating is always in kva.

Answer / shanmukh

cu losses of a t/f depends on current and iron losses are
depend on voltages total losses depending on volt ampere but
power factor of a t/f independent of total losses because
t/f rating in kva but not in kw

Answer / saeid

Watt is unite of work in physics.
When anything does some work, it will be described or
measured by KW. Then one of its specification is
KW . In oder words, KW is used for whatever equipment or
machine that does work. For example,generator, motor,
heater or a lump do work and they are identifying by KW. On
the other hand, a transformer doesn't
do any work. It only convert voltage and current while its
input energy is almost equal to its out put energy. In
fact, It’s not considered a source of power or a load for
power system. As a result, we use KVA to identify capacity
of a transformer instead of KW that can not be used
technicaly.
Additionally, I do not believe that this discussion is
related to power factor, copper loss or core loss of the
transformer.

Answer / hitesh chauhan

because transformer not consumes the power.It take the power
from input and its given to output.

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