Synchronous Generator

1
Synchronous Generator

• EE341 Energy Conversion
• Ali Keyhani
• Synchronous Machines
• lecture 1

2
AC Machines

• Generator

to

• Motor

to
Synchronous machines

• A.C machines

Induction machines
3
Sychronous Machines
a
a
b
c
N
I
f
a
b
c
S
b
c
b
c
a
P2

• Armature windings are located on the stator

I
f
V
f

• Field windings are located on the rotor

Fig. 1
4
Operation

• By rotating the field windings in the air gap, a
  rotating magnetic field is established in the
  machine. A balanced set of voltages is induced
  in the balanced three - phase windings located in
  the stator.

5
Coil (a-a')
a
ele
2
0
N
I
mech
f
I
f

ele
mech
S
S
mech
N

mech
ele
2

P
ele
mech
a
2
Fig. 2
6
(No Transcript)
7
Machine Eq. CKT
V
T
R
V
a
E
T

R
jX
a
s
I
f
V
V
f
jXs
E
a
E
c
E
b
R
a
R
a
jXs
jXs
b
c
8
E
jXs
V
T
E
P
jQ

1
7-1 Develop a table showing the speed of magnetic
field rotation in AC machines 2,4 and 6 poles
operating at frequencies 50,60 and 400Hz.
9
The Rotating Magnetic Field
Principle of Machine Operation

• If a three-phase set of currents, each with equal
  magnitude and differing in phase by 120 degrees,
  flows in an armature winding, then it will
  produce a rotating magnetic field of constant
  magnitude.

The flux wave will travel in the air gap at the
speed of
where
fe is the frequency of the three
phase currents.
a
c
a
b
V
Magnetic axis ref.
a
D
x
b
c
a
10
Assume
11
Flux will pulsate with the same
B
B

(x,t)
a
f
m
s
When X0
as applied voltage
B
a
(x,t)
Flux density varies around the stator periphery.
D
P
x
0
D
2
P
12
Note
13
The Induced Torque in AC machines
a
b
c
N
S
b
c
a
Rotor
Stator
Angle between B and B
s
R
14
For the previous figure

• Magnetic field waves are rotating in a
  counterclockwise direction.

• By applying the right hand rule, the induced
  torque is clockwise, or opposite the direction of
  rotation of the rotor.

• Machine acting as generator.