This preview shows pages 1–4. Sign up to view the full content.
1
ECE201 Linear Circuit Analysis I
Lecture 38
Topic:
Complex Power: Reactive & Apparent Power; Conservation of Power
1. Real Power
P
ave
=
V
eff
⋅
I
eff
⋅
cos
θ
Z
=
V
rms
⋅
I
rms
⋅
cos
Z
What are the meanings of P
ave
, V
eff
(V
rms
), I
eff
(I
rms
), and
Z
?
What are their units?
P
ave
is also called the
Real Power
, its unit is
watts
, or
W
.
2. Apparent Power
The quantity V
eff
· I
eff
is called the
Apparent Power
, its unit is
voltampere
, or
VA
.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document 2
3. Complex Power
(1) Complex power is a phasor:
eff
v
eff
VV
=
∠θ
i
eff
eff
θ
I
I
∠
=
*
eff
eff
I
V
S
×
≡
(Definition of complex power)
()
eff
v
eff
i
eff
eff
v
i
eff eff
z
eff eff
z
SV
I
VI
VI c
o
s
j
VI s
i
n
=∠
θ
×
∠
−
θ
=⋅
∠
θ
−
θ
=θ
+
θ
1442 4 4
31
4
42 4 43
P
ave
+
jQ
(2) complex
=
average
+ j
reactive
power
power
power
22
eff eff
z
eff eff
z
eff eff
SS
o
s
i
n
==
θ
+
θ
=
Therefore, the magnitude of the complex power is the apparent power in unit
(VA).
The reactive power:
{ }
QI
mS
=
(VAR)
volt
ampere
reactive
P
ave
=
Scos
θ
z
(
W
)
Q = Ssin
z
=
P
ave
tan
z
3
(3)
Relationships
Note the difference between real and complex numbers.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
This is the end of the preview. Sign up
to
access the rest of the document.
This note was uploaded on 04/19/2011 for the course ECE 201 taught by Professor All during the Spring '08 term at Purdue UniversityWest Lafayette.
 Spring '08
 ALL

Click to edit the document details