Chapter 11 : AC Power Analysis - PowerPoint Presentation, Engineering - Notes

 Page 1


‹#› EENG 224 
Chapter 11 
AC Power Analysis 
Huseyin Bilgekul 
Eeng224 Circuit Theory II 
Department of Electrical and Electronic Engineering  
Eastern Mediterranean University 
Chapter Objectives:  
? Know the difference between instantaneous power and average 
power  
? Learn the AC version of maximum power transfer theorem 
? Learn about the concepts of effective or Rms value 
? Learn about the complex power, apparent power and power factor   
? Understand the principle of conservation of AC power  
? Learn about power factor correction   
 
 
Page 2


‹#› EENG 224 
Chapter 11 
AC Power Analysis 
Huseyin Bilgekul 
Eeng224 Circuit Theory II 
Department of Electrical and Electronic Engineering  
Eastern Mediterranean University 
Chapter Objectives:  
? Know the difference between instantaneous power and average 
power  
? Learn the AC version of maximum power transfer theorem 
? Learn about the concepts of effective or Rms value 
? Learn about the complex power, apparent power and power factor   
? Understand the principle of conservation of AC power  
? Learn about power factor correction   
 
 
‹#› EENG 224 
An Electical Power Distribution Center 
Page 3


‹#› EENG 224 
Chapter 11 
AC Power Analysis 
Huseyin Bilgekul 
Eeng224 Circuit Theory II 
Department of Electrical and Electronic Engineering  
Eastern Mediterranean University 
Chapter Objectives:  
? Know the difference between instantaneous power and average 
power  
? Learn the AC version of maximum power transfer theorem 
? Learn about the concepts of effective or Rms value 
? Learn about the complex power, apparent power and power factor   
? Understand the principle of conservation of AC power  
? Learn about power factor correction   
 
 
‹#› EENG 224 
An Electical Power Distribution Center 
‹#› EENG 224 
Apparent Power and Power Factor 
1
2
cos( ) cos( )
m m v i Rms Rms v i
P V I V I ?? ?? = -= -
1
2
m m Rms Rms
S V I V I = =
Apparent Power
cos
Power Factor
()
v i
P
pf
Sp
S
Pf
??
= ×=
-
×
= =
? The Apparent Power is the product of the Rms value of voltage and current. It is 
measured in V olt amperes (VA). 
? The Power Factor (pf) is the cosine of the phase difference between voltage and 
current. It is also the cosine of the angle of load impedance. The power factor may 
also be regarded as the ratio of the real power dissipated to the apparent power of 
the load. 
? The Average Power depends on the Rms value of voltage and current and the 
phase angle between them. 
Page 4


‹#› EENG 224 
Chapter 11 
AC Power Analysis 
Huseyin Bilgekul 
Eeng224 Circuit Theory II 
Department of Electrical and Electronic Engineering  
Eastern Mediterranean University 
Chapter Objectives:  
? Know the difference between instantaneous power and average 
power  
? Learn the AC version of maximum power transfer theorem 
? Learn about the concepts of effective or Rms value 
? Learn about the complex power, apparent power and power factor   
? Understand the principle of conservation of AC power  
? Learn about power factor correction   
 
 
‹#› EENG 224 
An Electical Power Distribution Center 
‹#› EENG 224 
Apparent Power and Power Factor 
1
2
cos( ) cos( )
m m v i Rms Rms v i
P V I V I ?? ?? = -= -
1
2
m m Rms Rms
S V I V I = =
Apparent Power
cos
Power Factor
()
v i
P
pf
Sp
S
Pf
??
= ×=
-
×
= =
? The Apparent Power is the product of the Rms value of voltage and current. It is 
measured in V olt amperes (VA). 
? The Power Factor (pf) is the cosine of the phase difference between voltage and 
current. It is also the cosine of the angle of load impedance. The power factor may 
also be regarded as the ratio of the real power dissipated to the apparent power of 
the load. 
? The Average Power depends on the Rms value of voltage and current and the 
phase angle between them. 
‹#› EENG 224 
Apparent Power and Power Factor 
? Not all the apparent power is consumed if the circuit is partly reactive. 
Purely resistive 
load (R) 
?
v
– ?
i 
= 0,   Pf = 1 
P/S = 1, all power are 
consumed 
Purely reactive 
load (L or C) 
?
v
– ?
i 
= ±90
o
,     
pf = 0 
P = 0, no real power 
consumption 
Resistive and 
reactive load  
(R and L/C) 
?
v
– ?
i  
> 0 
?
v
– ?
i 
< 0 
• Lagging - inductive load 
• Leading - capacitive load 
P/S < 1, Part of the apparent 
power is consumed 
Page 5


‹#› EENG 224 
Chapter 11 
AC Power Analysis 
Huseyin Bilgekul 
Eeng224 Circuit Theory II 
Department of Electrical and Electronic Engineering  
Eastern Mediterranean University 
Chapter Objectives:  
? Know the difference between instantaneous power and average 
power  
? Learn the AC version of maximum power transfer theorem 
? Learn about the concepts of effective or Rms value 
? Learn about the complex power, apparent power and power factor   
? Understand the principle of conservation of AC power  
? Learn about power factor correction   
 
 
‹#› EENG 224 
An Electical Power Distribution Center 
‹#› EENG 224 
Apparent Power and Power Factor 
1
2
cos( ) cos( )
m m v i Rms Rms v i
P V I V I ?? ?? = -= -
1
2
m m Rms Rms
S V I V I = =
Apparent Power
cos
Power Factor
()
v i
P
pf
Sp
S
Pf
??
= ×=
-
×
= =
? The Apparent Power is the product of the Rms value of voltage and current. It is 
measured in V olt amperes (VA). 
? The Power Factor (pf) is the cosine of the phase difference between voltage and 
current. It is also the cosine of the angle of load impedance. The power factor may 
also be regarded as the ratio of the real power dissipated to the apparent power of 
the load. 
? The Average Power depends on the Rms value of voltage and current and the 
phase angle between them. 
‹#› EENG 224 
Apparent Power and Power Factor 
? Not all the apparent power is consumed if the circuit is partly reactive. 
Purely resistive 
load (R) 
?
v
– ?
i 
= 0,   Pf = 1 
P/S = 1, all power are 
consumed 
Purely reactive 
load (L or C) 
?
v
– ?
i 
= ±90
o
,     
pf = 0 
P = 0, no real power 
consumption 
Resistive and 
reactive load  
(R and L/C) 
?
v
– ?
i  
> 0 
?
v
– ?
i 
< 0 
• Lagging - inductive load 
• Leading - capacitive load 
P/S < 1, Part of the apparent 
power is consumed 
‹#› EENG 224