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Answer Posted / bhushan
kw IS THE POWER DRAWN BY A LOAD LIKE ELECTRIC
MOTOR,HEATER,FAN ETC,
WHEREAS kva IS THE POWER WHICH WE CAN GET FROM A POWER
CONVERTOR SOURCE LIKE INVERTER,UPS,DG ETC.
ALSO kw=kva*POWERFACTOR(VIcosǿ)
in the ideal conditions the power of the load is equal to
its KVA , but practically a phase difference will happen
between the volt and the current and it will lead to reduce
the KVA to the KW , the ratio between the KW power (Actual
power ) & the KVA (Appearent power) is the power factor .
In my opinion we can say the KVA is the theoritical value
of the power , and it can be equal to the Kw if no phase
difference happened.
KW means machanical power(mechanical load) o/p of the system
but KVA means electrical power output(electrical load)
kw is a real(Active) power that depends on the load that we
use.
KVA is a apparent power which is the maximum power that can
be produced by source.
KVA = voltage x current
KW= voltage x current x power factor
power factor depends upon load.
Apparent Power(KVA)= real power(KW) + reactive power(KVAr
The power consumed by the resistive element of the circuit
with Impedance is termed as Active Power
P= V*I*p.f.
P=I*Z*I*(R/Z)
P=square(I)*R in Wattd
The power consumed by the Impedance of the circuit is
called as Active Power
S=V*I
S=I*Z*I
S=square(I)* Z expressed in VA
kW is the unit of real power & kVA is the unit of Apparent
power.
Apparent Power= real power + reactive power
Looking at different electrical equipment you will notice
that the power ratings are either expressed in kVA
(kilo Volt Ampres) or sometimes in kW (kilo Watts). The
next question is what’s the difference? Both are
measurements of power however they are truly different.
To understand the differences consider how each are
derived. kW is called actual or real power, or simply
the amount of power that is available to do real work. kVA.
On the other hand kVA is known as “apparent”
power. This is because only a portion of the available kVA
may be available to do real work. The remainder
is simply excess current.
The difference between kVA and kW really depends on the
power factor (PF). When the voltage and
current are in phase with each other in an AC circuit, the
power factor is 1.0 or “unity”. The more the
voltage falls out of phase with the current the lower the
power factor becomes and the less “real power” or
kW the device uses; however it may still be using the same
amount of current as a device with a higher
power factor. Power factor will be "leading" or "lagging"
depending on which way the load shifts the
current’s phase with respect to the voltage’s phase.
Inductive loads cause current to lag behind voltage,
while capacitive loads cause current to lead voltage hence
leading or lagging power factor.
kVA = Volts x A
kW= Volts x Amps x Power Factor or [kVA x Power Factor]
The next question is why express the kVA value of a device
and what use is
kVA if only part of it can do work? The reason kVA is used
as a rating is
because the rating of an electrical device is dependent on
the amount of
current they can sustain. A kW rating does not indicate how
much current
a device can carry (as the power factor may not be known)
where kVA
does indicate the maximum current at a specific voltage
level.
| Is This Answer Correct ? | 9 Yes | 15 No |
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