Answer / manash senapati

Since,Copper loss of a transformer depends on Current and
Iron loss of a transformer depends on Voltage,hence total
loss of a transformer depends on volt-ampere and there is
no phase angle between current and voltage i.e. it is
independent of load power factor,that is the reason why
tranformer ratings in KVA not imn KW.

Answer / suryasish

In transformer there are two losses.Copper loss depends
upon current and core loss depends upon voltage.So the
total loss depends upon VA.It does not depend upon phase
angle between voltage and current,that means it is
independent of power factor.So the trnsformer rating are
given in KVA not KW.

Answer / pradyumna chandra panda

Why the Transformers are rated in KVA?
Ans . Motor is a consuming device it consume the power
(wt) so it is rated in KW. But the
Transformer is a static device which transfers
the power (Apparent power) from the
Generating point to the user. Apparent power is
the product of voltage and current
I.e. Increase voltage with decrease current and
decrease voltage with increase current. Power factor of the
load does not share with main losses (Iron and copper) it
affects the Active Power which share of apparent power.

Active power is the real power which the transformer
gives. Transformer should not be rated on the base of
Active power (KW) which is variable because the power factor
of the load is not knows before which to be connected across
the transformer.


Active power is equal to apparent power at resistivity load
where power factor is unit at cos Q is equal to zero degree.
Active power is decrease power where cos Q (not fi) is
increase
Therefore in simple we can say due to unknown power factor
of load, transformer and alternator are rated in KVA.
Hint – we know cos FI is the value of cos Q i.e. Apparent
power/ active power.


Transformer input is Apparent power in KVA----- In
Transformer Apparent Power is reduced by Iron loss (k) &
Copper loss --- On Transformer output Active power in KW



PRADYUMNA CHANDRA PANDA

BRG STEEL

Answer / gopi paranth

The Copper Loss of a transformer depends on current and iron loss depends on voltage.Hence total losses depends on "Volt ampere" (VA)only and it is independent of load powerfactor.That is Why the rating of transformer is given in KVA and not in KW

Answer / rashpal

transformer is design for particular voltage and current
therefore rating of transformer is in kva.

Answer / pradyumna chandra panda

Power given to the transformer is Apparent power (K)
it is the supply power of the power house and the power
given by the transformer to the Load is the true power or
Active power which is actual used by the load and rest is
the reactive power i.e. square of apparent power including
iron loss & copper loss in KVA = square of true power in KW
+ square of reactive power in KVAR. A sound transformer
efficiency is 98% (input power- Iron loss (k) & copper loss
= output power).
For full resistive load (at unity pf ) a 100 KVA transformer
gives 100 KW (approx.) true power, and for inductive power
at .8 pf the same will able to give 80 KW (approx.) true
power, but the types of load (its pf) is not know before
which to be connected across the transformer, this is only
why the transformers are rated in KVA and it is meaningless
to discuss about the iron loss and copper loss because the
Inventor and UPS are also rated in KVA.


In other hand or in simply we can say due to unknowing power
factor the transformer, generator etc are rated in KVA. In
heavy size transformer copper loss is more and it vary with
load and Clemet i.e. transformer oil condition but it is not
main reason to rating the transformer in KVA.


Pradyumna Chandra Panda
Berhampur Mob 9861357949

Answer / prasad

The power consumed depends upon p.f. or say power
consumed is Energy Input/ P.F.
The electrical energy reqd by system is thus sum of
product of Total power reqd & power factor of each load.
Basiclly Transformers & Generators are energy devices.
They supply electrical energy to various loads which
consume power. The unit of electrical energy is VA or KVA
or MVA

Answer / neeti singh

This is due to the fact that rated transformer o/p is
limited by heating and hence by the losses in transformer.
The two type of losses in transformer are core loss and
ohmic loss.
The core loss depends on transformer voltage(V) and ohmic
loss depends on current(I)As these losses depends upon V & I
and are almost unaffected by the load pf, the transformer
o/p is expressed in VA(V*I) or in kVA and not in kW.

Answer / ankita datta

the power is equal to volt*ampere*cos(power factor angle)
which is watt.but while establishing a machine we have to
kip in mind dat d cost is justified.transformers being
relatively cheaper it is not desirable to study the power
factor of d entire area as d cost wud become2high.so its
constructd wid nly v i knwn.den according 2locality d power
factor is checkd wen required.thus it is kva.generators on d
othr hand r in wattas dey r expensive.

Answer / elango

copper loss depends on current(I)iron loss depends upon
voltage(V). hence the total loss in a transformer depends
upon volt-ampere(VA)only and not on the phase angle between
voltage and current i.e,it is independ of load power
factor.that is why the rating of a transformer is given in
KVA and not in kw.

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