ECE321.
Spring 2009.
Exam 4 Solution Outline
Problem 1
1a) False
1b) True
1c) False
1d) True
1e) True
1f) False
1g) False
1h) False
1i) False
1j) True
Problem 2
Step 1  5 pts
w
as
25 sin 4
φ
sm
⋅
( 29
⋅
=
w
bs
25 cos 4
φ
sm
⋅
( 29
⋅
=
Step 2  5 pts
F
w
as
i
as
⋅
w
bs
i
bs
⋅
+
=
F
125 sin 4
φ
sm
⋅
( 29
sin 50 t
⋅
(
)
⋅
cos 4
φ
sm
⋅
( 29
cos 50 t
⋅
(
)
⋅
+
( 29
⋅
=
F
125 cos 4
φ
sm
⋅
50 t
⋅

( 29
⋅
=
Speed of MMF relative to stator is 12.5 rad/s CCW
Step 3  5 pts
Speed of MMF relative to rotor is thus 12.5 rad/s CCW   100 rad/s CCW = 112.5 rad/s
This is the mechanical speed relative to the rotor
Step 4  5pts
The frequency of the rotor currents will thus be 112.5 rad/s or
112.5
2
π
⋅
17.90493
=
Hz
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View Full DocumentProblem 3
Step 1  10 pts
W
c
1
2
i
T
⋅
L
ss
L
sr
cos
θ
r
( 29
⋅
L
sr
cos
θ
r
( 29
⋅
L
rr
⋅
i
⋅
=
where
i
i
as
i
ar
=
Step 2  10 pts
T
e
P
2
θ
r
W
c
d
d
⋅
=
T
e
P
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 Spring '08
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