PPT: Three Phase AC Circuits | Basic Electrical Technology - Electrical Engineering (EE) PDF Download

 Page 1


3-Phase AC Circuit
Page 2


3-Phase AC Circuit
Introduction
              Three phase system is a part of a 
poly phase system.The different circuits in 
polyphase system operate at same 
frequency, but their voltage and currents 
are out of phase from one other.
               In poly phase many number of 
phase are displaced from each other with 
appropriate angle of electrical degree.
Page 3


3-Phase AC Circuit
Introduction
              Three phase system is a part of a 
poly phase system.The different circuits in 
polyphase system operate at same 
frequency, but their voltage and currents 
are out of phase from one other.
               In poly phase many number of 
phase are displaced from each other with 
appropriate angle of electrical degree.
                Thus, an ac system having a group of 
poly phasers having equal voltage & frequency 
arregement with equal phase angle difference 
between adjacent phases is called a polyphase 
system.By considering many advantages of 
three phase system over single phase for bulk 
power handling, for all practical purpose, three 
phase system is universally employed for 
generation , transmission& distribution of 
electrical power. In addition to that the reason 
for immense popularity of three phase appartus 
are that (a) more efficiency (b) less material 
required for given capicity (c) less cost for 
same capacity than single-phase equipment.
Page 4


3-Phase AC Circuit
Introduction
              Three phase system is a part of a 
poly phase system.The different circuits in 
polyphase system operate at same 
frequency, but their voltage and currents 
are out of phase from one other.
               In poly phase many number of 
phase are displaced from each other with 
appropriate angle of electrical degree.
                Thus, an ac system having a group of 
poly phasers having equal voltage & frequency 
arregement with equal phase angle difference 
between adjacent phases is called a polyphase 
system.By considering many advantages of 
three phase system over single phase for bulk 
power handling, for all practical purpose, three 
phase system is universally employed for 
generation , transmission& distribution of 
electrical power. In addition to that the reason 
for immense popularity of three phase appartus 
are that (a) more efficiency (b) less material 
required for given capicity (c) less cost for 
same capacity than single-phase equipment.
Agvantages of 3-phase system 
over 1-phase
(1)Higher power/weight ratio of alternators.   
A three phase alternator is smaller and 
lighter that a single phase alternator of the 
same power output. Hence, it is also 
cheaper.
(2)A three phase transmission system 
requires less copper or aluminium to 
transmit the same quantity of power of a 
specific distance than a single phase 
system.
Page 5


3-Phase AC Circuit
Introduction
              Three phase system is a part of a 
poly phase system.The different circuits in 
polyphase system operate at same 
frequency, but their voltage and currents 
are out of phase from one other.
               In poly phase many number of 
phase are displaced from each other with 
appropriate angle of electrical degree.
                Thus, an ac system having a group of 
poly phasers having equal voltage & frequency 
arregement with equal phase angle difference 
between adjacent phases is called a polyphase 
system.By considering many advantages of 
three phase system over single phase for bulk 
power handling, for all practical purpose, three 
phase system is universally employed for 
generation , transmission& distribution of 
electrical power. In addition to that the reason 
for immense popularity of three phase appartus 
are that (a) more efficiency (b) less material 
required for given capicity (c) less cost for 
same capacity than single-phase equipment.
Agvantages of 3-phase system 
over 1-phase
(1)Higher power/weight ratio of alternators.   
A three phase alternator is smaller and 
lighter that a single phase alternator of the 
same power output. Hence, it is also 
cheaper.
(2)A three phase transmission system 
requires less copper or aluminium to 
transmit the same quantity of power of a 
specific distance than a single phase 
system.
(3)Three phase motors are self-starting due to the 
rotating magnetic field induced by the three phases. 
On the other hand, a single phase motor is not self 
starting, it requires a capacitor and an auxilliary 
winding.
(4)In Single phase systems, the instanteous 
power(power delivered at any instant) is not constant 
and is sinusoidal. This results in vibrations in single 
phase motors.
In a three phase power system, though, the 
instanteous power is always the same.
(5)Three phase motors have better power factor 
compared to single phase motors.
(6)Three phase supply can be rectified into dc supply 
with a lesser ripple factor