three-phase balanced system or load and

three-phase unbalanced system or Lord

are the two most commonly used concepts

in power system but what do we really

mean by a balanced or unbalanced

three-phase system what are the

parameters that decide whether a system

is balanced or unbalanced so if you want

to get the details and the basics of

three-phase balanced and unbalanced

system watch the video when we talk

about a three-phase balanced or

three-phase unbalanced system we must

first know a very basic thing that is it

is not the source that decide if a

system is balanced or unbalanced until

the winding of it of the sole generator

is placed or wrongly which is a very

rare case it is the load which it

decides if a system is balanced or

unbalanced now let's understand what is

a balanced system as we know in

three-phase system phase voltages or

current are displaced from each other by

120 degree this is because the winding

of a generator are placed 120 degree

apart from each other

consider a star connected windings as

shown in the figure if you would like to

know what is a star and Delta Connection

you can watch my video on that you will

get link for that video down in the

description now if you connect load to

it we can call it as a system let's say

we connected an equal load on each

winding as the load on my system is

identical

current flowing through each phase is

same and hence phase angle between

voltage and current is perfectly 120

degree apart from each other as shown in

the figure also if you if your load is

perfectly identical on all the three

phases current flowing through the

neutral is also zero if you observe the

diagram carefully you will find that the

sum of return currents in is zero at

every instance for example at instants

corresponding to two

40-degree IC is equals to maximum and IB

equals to I a is equals to minus 0.5

IMAX so if we add these written currents

we will get the sum equals to zero and

this is true for every instance and

hence we can say that there is no

current flowing through the neutral and

we can actually remove the neutral

conductor from the circuit without

affecting the voltage and current this

is only applicable for perfectly

balanced system that is system with

identical load on each phase and we can

call such system as a balanced system so

what are the properties of a balanced

system waveform is perfectly sinusoidal

that is in terms of magnitude and phase

shift of 120 degree current flowing

through each phase is same no current

flows through the neutral power loss is

very low or not present of course such

system is ideal and existing of which is

doubtful most of the system are

unbalanced like our distribution system

and the properties of unbalanced systems

are completely opposite of what we have

seen just now now let's increase the

load on one of the phase of our system

as we have increased the load on one

phase it will draw more current than the

other two phases and this will create

imbalance in the system and here you

will need the neutral conductor the

waveform is now disturbed in terms of

magnitude and phase shift this will

further cause the power loss in the

system generally the system gets

unbalanced because of these reasons

unbalanced in winding of a three-phase

equipment like three-phase induction

motor

if the reactance of the three windings

are not same then it will draw an equal

current tunnel system and the second one

is an equal load on the system this

causes more current to flow through one

particular phase on which the extra load

is connected these are the two main and

the basic causes of unbalance in a

system such kind of animal

scauses heating of three-phase machines

further this will decrease their overall

life this imbalance will also increase

the I square R losses also unbalanced

system may cause tripping of variable

frequency drives used for induction

motor you will see in our distribution

system a neutral is always provided as

load on the faces is not defined or

equal and different faces draw different

current which makes the distribution

system unbalanced let's check out the

properties of an unbalanced system

waveforms are disturbed in terms of

magnitude and phase angle current

flowing through phase is not same

neutral is needed power losses are more

now let's find out whatever we have seen

till now is correct or not whether

increasing load honest any phase of a

three-phase system will make system

unbalanced we'll find that out in MATLAB

so this is our three-phase souls and

this little block here will measure the

current flowing through our system now

pool of this is given to the scope which

will show us the waveform of current and

this is our three phase load for

understanding purpose I have made this

load purely resistive and equal which

here you can see let's find out if the

system is balanced or not as you can see

the waveform we have got here is

perfectly balanced in terms of magnitude

and phase angle so we can call this

system as balanced system now let's

check out if we increase the load on any

one of the phase then what will happen

let's also add some inductive power

as you can see the waveform is now

completely disturbed in terms of

magnitude and phase angle and this

system is definitely a unbalanced system

so I hope you guys have understood what

is balanced and unbalanced system this

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watching

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