Answer / wenceslaus hhindo

Since transformer has two major losses that iron losses
depend in voltage and copper losses whic depend on
current,so the current is measured in amp and the voltage
is measured in voltage then this combination makes va which
is the rating of transformer.Hens that is why transformer
rated in KVA.

Answer / sandy

30Ma mean how much Amp?

Answer / akash jain

because the both of the losses are independent so,that
transformer rating is in kva....

Answer / swpan kumar bhowmik

As seen, Cu loss of a transformer depends on current and
iron loss on voltage. Hence, total transformer loss depends
on volt-ampere (VA) and not on phase angle between voltage
and current i.e. it is independent of load power factor.
That is why rating of transformer is in kVA and not in kW.

Answer / sarvesh singh

Transformer rating is done in kva because this rating is
true from either side i.e. either from primary side or
secondary. Also due to cu-losses and self inductance in
primary and secondary, unity power factor is not maintained
and hence it can't be same from either side.

Answer / visakh

there are 2 kinds of losses in Xfr core & cu losses...we cannot represent the efficiency of a xfr by simply mentioning cu loss as it occurs only when the load is applied...whereas the core is always magnetized whether load is connected or not...so here we consider all day efficiency, where we take into account both losses...so we represent in kva

Answer / vidhya joseph

transformer is neither an energy producing device nor an
energy consuming device. so no point of specifying the
ratings of prime mover. so only calculation needed is
losses. lossesdepend on kva rating only. independent of pf.
in case of a generator we need to calculate losses as well
as the rating of prime mover.losses depend on kva and prime
mover rating depends on active power output. so need to
specify kw or pf also. this condition doesnot arise in case
of transformer because no prime mover
so no need to spcify kw and pf. only kva rating isneeded

Answer / jenish

i think reason for rating in kva is
v=voltage give us a measure of core material and its size
and
i= current give us measure of copper wire and hence size of insulation of conductor.
so by knowing kva we can estimate the size of transformer
and answer related to losses is also right...

Answer / manoj prabhakar

1> 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..

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

3> In all A.C. machines (which includes motors whose rating
are in KW )iron losses are proportional to voltage & copper
losses are proportional to current.
The machine rating is given in terms of its output. The
transformer output is electrical energy & thus its rating
is same as energy i.e. KVA.
Same is the case with generator

4> 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 / t.swetha

Iron losses depend on the system voltage, I^2R losses
depend on current but both not on power factor so the
rating of transformer is in kVA.

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