Why transformer rating is represent in KVA?

Answer Posted / 7anoter4

A power transformer contains two main part –the windings-
copper or aluminum conductors insulated –and the magnetic
core.

Magnetic core requires an excitation current in order to
maintain the required magnetic field.

The excitation current depends on supplied voltage and if
the supplied voltage is over a certain limit the excitation
current presents a threshold and start to be very high.
This voltage is the rated voltage.

On the other hand, the conductor insulation rated
temperature is limited-according to insulation class-since
above this limit the insulation will be damaged.

The temperature arise depends of the current passing
through conductor and producing heat losses. These losses
depend only on the absolute value of the current and it is
not connected to the active load [kw=volt*current*p.f. then
the maximum kw it is when p.f.=1 then kw=kVA].

The product of voltage with current is measured in VA or
kVA=1000 VA or MVA=1000000 VA.

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