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Question
`WHY THE GENERATOR RATING IN KVA & MOTOR RATING IN KW?`
Question Submitted By :: Electrical-Engineering
I also faced this Question!!     Answer Posted By

# 1
Transformer and genrator PF depends on the nature of
connected load ( Motor ), But motor has its own fixed Power
factor

Therefore Transformer and genrator capacity shown in KVA (
Without PF ) and motor Capacity shows in Kw ( with power
factor )

 Is This Answer Correct ? 175 Yes 20 No
Ravi - Cement Plant India

# 2
Generator is producer of Voltage and Current, we can
willl rated in terms of product of V*I, secondly it gives a
electrical output for any Load(may Capacitor,Inductor &
resistor),so it is consider as Procuct of Voltage & Current
excluding powerfactor.
Whereas motor is machines coverts electrical Energy to
Mechanical energy, so it is rated in KW

 Is This Answer Correct ? 156 Yes 48 No
Balaji

# 3
Generator and transformer are rated in KVA becoz at that
time we dont know the consumer power factor as we know that
the (KW= KVA X Cos Phi) as we know the power factor we have
ratings in KW and on the other hand motor has defined power
factor and the rating has been mentioned in KW for example
if we have transformer of rating 50KVA this rating of
transformer is its apparent power that is KVA if we
multiply the same withh the power factor 0.85 we will get
the real power that is KW

KW= KVA X Cos phi
KW = 50 X 0.85
KW= 42.5KW

 Is This Answer Correct ? 55 Yes 9 No
Zulfiquar Wani

# 4
Generator is a source of power. It includes active as well
as reactive power. It deliver only active power while
working on unity power factor. It deliver reactive power
only while connected to a purely reactive load. It can
deliver both of these powers while connected to a composite
load. This signifies that the current limit is the main
factor here. You can draw a purely rective current of rated
value or purly active current of rate value. combination of
output depends upon the load but the maximum limit is
prescibed.
When you are drawing both of the currencts active and
reactive, in such condition how much the alternator can
deliver? it can be descibed by KVA only not by KW. That is
why alternators are rated in KVA.
Motors are rated in KW only because for motors the load is
mechanical and thus only active power which is converted to
mech. is significant.The power factor of the motor is
independent of the load and at whatever powerfactor it
works it is due to its desing.

 Is This Answer Correct ? 61 Yes 18 No
P Tiwari

# 5
Generator rating is given in kVA,as generator is the souce
or capacitive.A 10 MVA generator will deliver 10 MW load if
power factor is unity,however if the power factor of the
load is 0.8 then generator can deliver active power up to
8MW only.It is up to user who efficienly generator power
may be utilised. Therfore, manufacturer always specify the
generator rating in KVA or MVA.

On the other hand, motor converts electrical energy into
mechanical energy.Therfore,its rating is given in KW as
power factor of the motor remain constant.

 Is This Answer Correct ? 7 Yes 0 No
Sdvyas

# 6
The rating of generator is described in terms of KVA by its
manufacturer because the generator will produce a constant
voltage on which it is designed and the current will depend
current for poor power factor and less current for unity
power factor, since the manufaturer does not know the
nature of load he desribed its rating in terms of voltage
and current.

While in case of motor, motor have fixed power factor.

 Is This Answer Correct ? 7 Yes 1 No
Yajnesh

# 7
We all know that the factor "Power factor" comes only when
the voltage & current waves are travelling at a time
difference. This will happen due to the
inductive /capacitive nature of the load(Depends how the
first (inductive)or current first(capacitive).

But at the time of producing the power, voltage and current
waveforms are starting from the source at the same time
only. Hence the question of power factor does not arise...

Hence DG is rated in kVA only...

Pls clarify ...

 Is This Answer Correct ? 14 Yes 12 No

# 8
Any device is rated depending on losses of the machine. In
a transformer the losses are iron losses which depend on
voltage and copper losses which depend on current so there
are no losses which depend on power factor hence
transformer is rated in KVA.the same thing applies for
generator aswell.

 Is This Answer Correct ? 2 Yes 0 No
Iftikhar Ahmed

# 9
generators and trasformers are rated i kva.kw=kvaxcos
(phi).the manufacture didn't no custmor load(in kw).one
more answer iron losses depends on supply voltage and cu
losses on current.so taht kvxi=kva

 Is This Answer Correct ? 24 Yes 23 No
Mohan

# 10
bcz the output in kw. is dependent on p.f. and kva o/p.
independent of p.f.for example asingle phase alternator
drawing 50 amp atunity p.f. at 230v has an o/p. of
(50*230)=11.5kw at unity p.f: (50*230*0.6)=9.6kw.at
0.8 p.f.and (50*230*0.6)=9.6kwat 0.6 p.f. but the kva
rating of alternator is (230*50)=11.5kva.

 Is This Answer Correct ? 1 Yes 0 No
Hiren

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