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CH 4 AC Generator
Pg215
AC Generator
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1. 交流發電機原理
2. 交流發電機相位原理
3. 交流發電機磁場控制
4. 交流電機頻率與轉速
5. 損失
6. 電壓調整率
DC machine basics
X
X
Force
South
pole
X
Angular velocity
X
Zero Force
North
pole
AC Generator
Phasor 相量
phasor
Sin
AC Machinery Fundamentals
V (t )  Em sin 
 Em sin t
i (t )  Im sin 
 Im sin t
 Em sin 2ft
 Im sin 2ft
Frequency:
1
f 
T
(cycle
sec
)
1
,T 
f
(sec
cycle
)
4.1 A Simple Rotation Loop
eind  (V  B )  L
 B  v sin 
Fig.4-1
eind  eba  ecb  edc  ead
 Bv sin ab  0  Bv sin cd  0
 2 Bv sin 
Tangential velocity v:
v  r   t
eind  (V  B )  L
 B  v sin 
eind  2 Br sin t
 AB sin t
  max sin t
The voltage is a sinusoid magnitude .
The Torque Induce
in a Current-Carrying Loop
  Fr sin 
( F  Bi )
ind  ab  bc  cd  da
 Bir sin   0
 Bi sin   0
 2 Bir sin 
  k Bloop  Bs
4.2 Rotating Magnetic Field
iaa' (t )  Im sin t
Fig.4-8
ibb' (t )  Im sin( t  120)
icc ' (t )  Im sin( t  120)
Rotating Magnetic Field
 0
0
  90
0
Frequency & Rotational Speed
2 Pole :
fe  fm
e  m
4 Pole :
fe  2 fm
 e  2 m
Frequency & Rotational Speed
P Poles :
P
fe 
fm
2
P
e  m
2
P
e  m
2
4.7
Losses
1. Copper Losses:
2
PSCL  3  I A RA
2
PRCL  3  I F RF
Pout

 100%
Pin
Pin  Ploss

Pin
2. Core losses
2
a. hysteresis loss
B
b. eddy current loss
n1 .5
3.Mechanical Losses
4.Stray Losses
(Miscellaneous Losses )
Pcon
Losses
Generator
Pcon 
Motor
 ind
m
 ind

m
4.8 Voltage Regulation
VR 
Vnl  V fl
V fl
 100%
Speed Regulation
SR 
nnl  n fl
n fl
100%
 nl   fl
SR 
100%
 fl