Hi friends in this video we are going to
see power consumed in a 3 phase circuit
in AC circuit power is given as voltage
multiplied by current rather in DC also
the same expression is true but in AC
circuit we have three types of powers
namely P Q and S P is called as an
active real or true power Q is reactive
power and S is apparent power all these
three powers are present in a circuit so
let's list out one by one first is
active real or true power it is given as
P equal to 3 v ph I ph cos phi ph v ph i
ph cos phi ph is the power consumed by a
single phase circuit but it is a three
phase therefore multiplication by three
same expression we can write in terms of
line quantities also so in terms of line
quantities P is root 3 VL IL cos phi PH
one thing you have to remember over here
5ph here as well as here it's same and
that is nothing but angle between v ph
and i ph so the problem with this
expression is here you are considering a
line quantities but whenever you are
consider angle that is not between VL
and IL but it is between v ph and I pH
so any whichever way you
should know where is the V Ph and I Ph in
order to get phi ph so better we use
this expression because here everything
is a phase quantity the unit of active
real or true power is watt or kilowatt
or sometimes we go higher unit that is
megawatt lets go to second type of
power that is reactive power that is
given as Q equal to 3 v ph i ph sin phi
ph once again you can write this in
terms of line quantities root 3 VL IL
sin phi ph same story repeats over here
Phi ph is the angle between v ph and I
ph hence better we remember this
expression unit for reactive power is
volt-ampere reactive or kilo volt ampere
reactive or higher unit you can consider
mega volt-ampere reactive lets go to
third type of power that is apparent
power
it is given by S equal to 3 times V pH
into I pH in terms of line quantities S
equal to root 3 V L into L unit for
apparent power is volt-ampere or kilo
volt ampere or mega volt and P R now lets
 draw a power triangle with the help
of this so lets consider first
inductive circuit and then capacitive
circuit so power triangle for inductive
circuit will be like this this is P
this is Q and hypotenuse is S phase
angle Phi is the angle between S and P
already we discuss this P is 3 vph iph
cos phi ph or cos phi you can say Q is 3
v ph I pH sine Phi pH or sin Phi and s
is 3 v ph i ph and here
Phi is the phase angle cos of Phi will
be the power factor its a inductive
circuit
hence the nature will be lagging that
means current lacks voltage by angle Phi
obviously current and voltage here are
the phase quantities for capacitive
circuit the power angle will be like
this
once again P is active power given by
3 vp h I  ph cos phi ph or cos phi Q
is 3 vph I ph sin phi and S is 3 v ph
I ph Phi once again a power factor angle
or phase angle and cause of it is power
factor it is a capacitive circuit
hence the nature is leading so here
we have seen a three-phase power and
power triangle associated with inductive
as well as capacitive circuit thank you
