power electronics basics Three Phase Inverters.ppt

Three Phase Inverters
Sub:- Power Electronics
Class: TE A
Mrs. S. R. Ghorpade
(2017-18)

Three-Phase Inverters
Consider three single-phase inverters in
parallel, driven 120° apart.

Three-Phase Inverter (continued)
Three single-phase full bridge inverters
12 transistors, 12 diodes, 3 transformers
Could it be simpler?

Alternative (Preferred) Configuration
6 transistors, 6 diodes
conduction for 120° or 180°

180° Conduction
• Three transistors ON at a time

Waveforms for 180 Conduction

Phase Voltages for 180 Conduction

Mode 1 Operation
1
1
1
3
2 2
2
3
2 3
2
3
eq
s s
eq
s
an cn
s
bn
R R
R R
V V
i
R R
V
i R
v v
V
v i R
  
 
  

 
0
3
t


 
Q1, Q5, Q6 conduct

Mode 2 Operation
2
2
2
3
2 2
2
3
2
3
2 3
eq
s s
eq
s
an
s
bn cn
R R
R R
V V
i
R R
V
v i R
V
i R
v v
  
 
 


  
2
3 3
t
 

 
Q1, Q2, Q6 conduct

Mode 3 Operation
2
3
t

 
 
3
3
3
3
2 2
2
3
2
2
3
eq
s s
eq
an bn
s
cn
R R
R R
V V
i
R R
i
v v
V
v i R
  
 
 

 
Q1, Q2, Q3 conduct

Fourier Series for Line-to-Line Voltages
1
5 5
6 6
5
6 6
1,3,5,...
( cos( ) sin( ))
2
1
( ) ( )
4
sin( )sin( )
2 3
4
sin sin ( )
3 6
o
ab n n
n
n s s
s
n
s
ab
n
a
v a n t b n t
b V d t V d t
V n n
b
n
V n
v n t
n
 
 
 
 

 

 







  
 
 
  
 
 
 

 

 


For the other Line-to-Line Voltages
1,3,5,...
1,3,5,...
4
sin sin ( )
3 2
4 7
sin sin ( )
3 6
s
bc
n
s
ca
n
V n
v n t
n
V n
v n t
n
 


 






 
 



Line-to-Line rms Voltage
1
2 2
3
2
0
2
( )
2
2
0.8165
3
L s
L s s
V V d t
V V V



 
 
 
 
 
 


rms value of the nth Component
1
4
sin
3
2
1
4 sin 60
0.7797
2
s
Ln
s
L s
V n
V
n
n
V
V V






 
Fundamental Component

Line-to-Neutral Voltages
2
0.4714
3
3
s
L
p s
V
V
V V
  

Phase Voltages (Y-connected load)
1,3,5,..
1,3,5,..
1,3,5,..
4
sin( )sin( )
3
3
4 2
sin( )sin ( )
3 3
3
4 4
sin( )sin ( )
3 3
3
s
aN
n
s
bN
n
s
cN
n
V n
v n t
n
V n
v n t
n
V n
v n t
n



 


 









 
 




Line Current for an RL load
2 2
1,3,5,...
1
4
sin sin( )
3
3 ( )
tan
s
a n
n
n
V n
i n t
n R n L
n L
R

 
 





 
 
 
 
 

 
 
 
 
  
 


DC Supply Current
IL=√3Io is the rms load line current
Vo1= fundamental rms output line voltage
Io is the rms load phase current
Θ1 = the load impedance angle at the fundamental
1
1
1
1
( ) ( ) ( ) ( ) ( ) ( )
....
3 cos( )
3 cos( )
s s ab a bc b ca c
o
s o
s
o
s L
s
v i v t i t v t i t v t i t
V
I I
V
V
I I
V


  



Three-Phase Inverter with RL Load

power electronics basics Three Phase Inverters.ppt

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