1
CHAPTER 16
Solutions for Exercises
E16.1
The input power to the dc motor is
loss
out
source
source
in
P
P
I
V
P
+
=
=
Substituting values and solving for the source current we have
3350
746
50
220
+
×
=
source
I
A
8
.
184
=
source
I
Also we have
%
76
.
91
3350
746
50
746
50
%
100
=
+
×
×
=
×
=
in
out
P
P
η
%
35
.
4
%
100
1150
1150
1200
%
100
regulation
speed
=
×
−
=
×
−
=
−
−
−
load
full
load
full
load
no
n
n
n
E16.2
(a)
The synchronous motor has zero starting torque and would not be
able to start a highinertia load.
(b)
The seriesfield dc motor shows the greatest amount of speed
variation with load in the normal operating range and thus has the poorest
speed regulation.
(c)
The synchronous motor operates at fixed speed and has zero speed
regulation.
(d)
The ac induction motor has the best combination of high starting
torque and low speed regulation.
(e)
The seriesfield dc motor should not be operated without a load
because its speed becomes excessive.
E16.3
Repeating the calculations of Example 16.2, we have
(a)
A
40
05
.
0
2
)
0
(
=
=
=
+
A
T
A
R
V
i
N
24
40
)
3
.
0
(
2
)
0
(
)
0
(
=
=
+
=
+
A
Bli
f
m/s
333
.
3
)
3
.
0
(
2
2
=
=
=
Bl
V
u
T
(b)
A
667
.
6
)
3
.
0
(
2
4
=
=
=
Bl
f
i
load
A
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2
V
667
.
1
)
667
.
6
(
05
.
0
2
=
−
=
−
=
A
A
T
A
I
R
V
e
m/s
778
.
2
)
3
.
0
(
2
667
.
1
=
=
=
Bl
e
u
A
W
11
.
11
)
778
.
2
(
4
=
=
=
u
f
p
load
m
W
222
.
2
2
=
=
R
i
p
A
R
W
33
.
13
)
667
.
6
(
2
=
=
=
A
T
t
i
V
p
%
33
.
83
33
.
13
11
.
11
%
100
=
=
×
=
t
m
p
p
η
(c)
A
333
.
3
)
3
.
0
(
2
2
=
=
=
Bl
f
i
pull
A
V
167
.
2
)
333
.
3
(
05
.
0
2
=
+
=
+
=
A
A
T
A
I
R
V
e
m/s
611
.
3
)
3
.
0
(
2
167
.
2
=
=
=
Bl
e
u
A
W
222
.
7
)
611
.
3
(
2
=
=
=
u
f
p
pull
m
W
667
.
6
)
333
.
3
(
2
=
=
=
A
T
t
i
V
p
W
5555
.
0
2
=
=
R
i
p
A
R
%
31
.
92
222
.
7
667
.
6
%
100
=
=
×
=
m
t
p
p
η
E16.4
Referring to Figure 16.15 we see that
125
≅
A
E
V for
2
=
F
I
A and
.
1200
=
n
Then for
1500
=
n
, we have
V
156
1200
1500
125
=
×
=
A
E
E16.5
Referring to Figure 16.15 we see that
145
≅
A
E
V for
5
.
2
=
F
I
A and
.
1200
=
n
Then for
1500
=
n
, we have
V
3
.
181
1200
1500
145
=
×
=
A
E
rad/s
1
.
157
60
2
=
×
=
π
ω
n
m
Nm
49
.
47
1
.
157
746
10
=
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 Fall '06
 Preston
 Electric motor, Radj

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