Answer / meenakshi

tranformers are rated based on the losses.the two main
losses of a transformer are copper loss n iron loss.copper
loss occurs in transformer whenever it is loaded(full load,
half load or whatever the load may be).thus copper loss
depends on current.but iron loss are constant losses,which
vil always be present no matter the transformer is loaded
or not.thus the total losses of a transformer depends on
volt-ampere n not on the phase angle between them. i.e it
is independent of load power factor.

Answer / amit rajak

The transformer is rated in KVA because its efficiency
actully depends on its losses.

and it is known that there are two main types of losses
that occurs in transformer.

They are as follows.
1.iron losses oer hysterisis losses
or Electromagnetic losses
2.copper losses or eddy current losses.

1. iron losses- it generrally occurs at the
windings that is made of copper as conductor and are under
operation . at all the loads and are rated in current
losses.

2. voltage losses-these losses generally occours at
all the time whether at load or not load conditions

so it is clear that this to parameters current and voltage
decides the overall efficiency of the transformers.

and also as the transformers deals with the poiwer in kilos

so it is rated in kilo volt amperes

Answer / jameel

the design of windings of transformer depend on the voltage
and current that is meaning kva .
morover the transformer hasnot mechanical output load such
as motor to say the power in kw.
only we calclate iron losses and copper losses in kw.
also the power factor in windings changes according to the
loads which connection in the secondary windings
usually trasformer and generator rated power in kva but the
motor in kw which is the useful power or active power.

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