Answer / tulasidhar

Transformer rating is KVA Instead of KW.bcoz P.f is does not depend.

Answer / satish r chude

cupper lose dependance upen the voltage and iron lose
depend upen the current. the total tx lose in volt and
current volt amper.VA.

Answer / loboreliance2003

S(kVA)=P(kW)+jQ(kVAr) where S is total power, P is active
power (Power uses by a resistive load E.g:light, heater,
etc) & Q is reactive power (Power causes by an inductive
load E.g: Induction motor). For a load, we only wants to
know how much work it will do, so information of kW is
enough. However, for a transformer as it has to supply
power to the whole system, it will be affected by both
active & reactive power. So you will have to concern about
the total kVA of your system to choose the correct
transformer. If you only concern about the active power the
transformer can handle and not about the reactive power,
the total power of your system sometimes will be larger
than the total power of the transformer and will damage it.

Answer / yogesh

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 in KVA.

Answer / m.omar javaid

Its rating is in kva since it does'nt involve any phase
difference b/w v and i i.e pf independent.manufacturers do
not take into account what type of load is to be
connected ,it could either be resistive or reactive.

Answer / pushpendra

Due to losses in transformer ,Because Full load loss(copper
loss)in term of current & No load loss(iron loss)is in term
of vollage .

Answer / sunam yadav

due to true power p = VI

Answer / sankar maiti(b.tech ee)

cupper lose dependance upen the voltage and iron lose
depend upen the current. the total tx lose in volt and
current volt amper.VA.

Answer / sadik pasha

copper losses depends on current and iron losses depends on
voltage so efficency of t/f depends on these two losses so
t/f's rated in KVA.

Answer / jey

Transformers and Generators are rated in KVA bcoz PF cannot be calculated( Cu loss depends on Voltage & Iron loss depends on Current). Always the Source end i.e transformer , Generator, power factor cannot be calculated and it is rated as KVA and Destination end i.e is Utility side such as Motor are rated as KW

PLEASE SEND THE PREVIOUS YEARS QUESTION PAPERS OF RRB JUNIOR ENGINEER-ELECTRICAL

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