Answer / raja

bcz....transformer does nt depens upon the power factor
that y ratings r in kva

Answer / r.emanuel james

Rating of the equipment connected to T/F depends upon the
power factor since the load power factor to which
T/F is supplying power is not known , it may be any type
of load (capacitive ,resistive , or inductive) that is why
its rating is mentioned in KVA

Answer / arvind singh

kVA is the unit for apparent power. Apparent power consists
of active and reactive power. Active power is the share of
the apparent power which transmits energy from the source
(generator) to the user. Reactive power is the share of the
apparent power which represents a useless oscillation of
energy from the source to the user and back again. It
occurs when on account of some »inertia« in the system
there is a phase shift between voltage and current. This
means that the current does not change polarity synchronous
with the voltage. But the heat generated in a winding as
well as the eddy current losses generated in a transformer
core depend on the current only, regardless of whether it
aligns with the voltage or not. Therefore the heat is
always proportional to the square of the current amplitude,
irrespective of the phase angle (the shift between voltage
and current). So a transformer has to be rated (and
selected) by apparent power.

Answer / ahmad mukhtiar

Transformer manufacturers design transformers on the basis
of no. of turns such that primary NI = secondary NI. Also
primary VI = secondary VI. The manufacturers design
transformers for Maximum (constant for every transformer)
power. As we know
KW = KVA x power factor
So for unit power factor
KW = KVA
and if load is inductive/capacitive then
KW < KVA

Manufacturers do not know whether transformer would be used
for inductive/capacitive/resistive load.

Answer / vipul rajput

1) X'mer is static device.
2)Power factor is not consider in case of transformer..so
its rating depend only on current & voltege.

P=V.A (p.f. is not consider)

Answer / jugal

As rating unit of any equipment depend upon the factora
which influence its output,and output depend upon the
losses. so as in transformer the cupper loss depend upon
current and iroin loss depend upon the vlotage,and not on
powerfactor.
as we know kw= volt*current8power factor
and Kva= vlot*amp
so its very logical; to rate the transformer in KVA

Answer / akash pandey

if a transformer is of X VA then it means that this is the
burden of secondary side and also we knoe that this output
power is limited by the losses namely the core loss
depending on V and ohmic losses depending on I hence the
rating is given in VA. Consider a case where the power
factor of the load is ZERO hence the power delivered will be
zero but losses will still be there ...hence the output
varying with the condition ...but whats constant is VA.

Answer / yogesh kumar

kVA is the unit for apparent power. Apparent power consists
of active and reactive power. Active power is the share of
the apparent power which transmits energy from the source
(generator) to the user.
Reactive power is the share of the apparent power which
represents a useless oscillation of energy from the source
to the user and back again.
It occurs when on account of some »inertia« in the system
there is a phase shift between voltage and current. This
means that the current does not change polarity synchronous
with the voltage. But the heat generated in a winding as
well as the eddy current losses generated in a transformer
core depend on the current only, regardless of whether it
aligns with the voltage or not. Therefore the heat is
always proportional to the square of the current amplitude,
irrespective of the phase angle (the shift between voltage
and current). So a transformer has to be rated (and
selected) by apparent power.

Answer / omnarayan tiwari

kVA is the unit for apparent power. Apparent power consists
of active and reactive power. Active power is the share of
the apparent power which transmits energy from the source
(generator) to the user. Reactive power is the share of the
apparent power which represents a useless oscillation of
energy from the source to the user and back again. It
occurs when on account of some inertia in the system there
is a phase shift between voltage and current. This means
that the current does not change polarity synchronous with
the voltage. But the heat generated in a winding as well as
the eddy current losses generated in a transformer core
depend on the current only regardless of whether it aligns
with the voltage or not. Therefore the heat is always
proportional to the square of the current amplitude
irrespective of the phase angle (the shift between voltage
and current). So a transformer has to be rated (and
selected) by apparent power.

Answer / joy das gupta

In X-former two losses- Cu loss and Iron loss.Hence Cu loss
depends on Current(A) and Iron loss depends on
Voltage(v).There is no phase angle between them. Again in
the output side of the X-former, we don't know the types of
load(Inductive , Capacitive, Resistive) which is connected
with secondary coil. Though it is not, we cant fixed the
power factor and it can vary. So under consideration of
losses and avoid the load pf variety, the transformer rating
given in KVA.

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