Transcript Lesson 20: Non-Linear Operation of Compound motors
Slide 1
Lesson 20 332a.pptx
ET 332a
Dc Motors, Generators and Energy Conversion Devices
LESSON 20: NON-LINEAR OPERATION OF
COMPOUND MOTORS
1
Slide 2
Lesson 20 332a.pptx
LEARNING OBJECTIVES
After this presentation you will be able to:
Determine the operating point of a dc compound motor
Observe the effect of driving a constant torque load on
motor performance
Compute the value of field resistance to produce a
given speed
Solve non-linear dc motor problems given a
magnetization curve.
2
Slide 3
Lesson 20 332a.pptx
NON-LINEAR COMPOUND MOTOR
CALCULATIONS
Example 20-1: Compound motor with non-linear magnetic circuit. Ten
percent of series field used to offset armature reaction.
240 V, 125 HP, 850 rpm, Ra = 0.0172 ohms RIP = 0.005 ohms
Series field resistance Rs = 0.0023 ohms
Shunt field resistance Rf = 49.2 ohms
Series field turns Ns = 4.5 t
Shunt field turns Nf = 577 t
Efficiency at rated load 85.4%
Drives a constant torque load
Compute a.) If b.) Ia c.) developed torque d.) Ia when a series R is
added to increase speed to 900 rpm. e.) The field resistance in series
with the shunt coil to produce the 900 rpm speed.
3
Slide 4
Lesson 20 332a.pptx
EXAMPLE 20-1 SOLUTION (1)
Ns = 4.5 t
Interpole
RIP 0.005 W
Load
T= constant
Ra
Series Field
Magnetization
curve given in
figure 11-7 in text
Rs
0.0023 W
???? W
Rx
0.0172 W
Rf
49.2 W
Ea
240 V
VT
Shunt Field
n1 = 850 rpm
Nf = 577 t
Answer a.)
Find Ia from rated output power and
efficiency
4
Slide 5
Lesson 20 332a.pptx
EXAMPLE 20-1 SOLUTION (2)
Answer b.)
5
Slide 6
Lesson 20 332a.pptx
EXAMPLE 20-1 SOLUTION (3)
Answer c.)
6
Slide 7
Lesson 20 332a.pptx
EXAMPLE 20-1 SOLUTION (4)
Part d.) Ia2 = ??? Use Fig 11-7 to find the total field mmf.
Motor Magnetizing Curve
1.2
f net
F lu x D e n sity (T )
.88
1000
1
0.8
0.6
0.4
0.2
0
0
1
2
3
4
5
6
7
mmf (in 1000 A-t/pole)
7
Slide 8
Lesson 20 332a.pptx
EXAMPLE 20-1 SOLUTION (5)
For non-linear operation, torque in proportional to Bp∙Ia
For constant torque load, TD1 = TD2
Solve for Ia2
This relates Ia2 to Bp2
Need another equation
8
Slide 9
Lesson 20 332a.pptx
EXAMPLE 20-1 SOLUTION (6)
Use speeds n1= 850 rpm n2=900 rpm. Speed is inversely proportional to
Bp.
Speed
Ratio
9
Slide 10
Lesson 20 332a.pptx
EXAMPLE 20-1 SOLUTION (7)
10
Slide 11
Lesson 20 332a.pptx
EXAMPLE 20-1 SOLUTION (7)
Solve the quadratic equation using the quadratic formula
11
Slide 12
Lesson 20 332a.pptx
EXAMPLE 20-1 SOLUTION (8)
Part e.) Find the value of Rx to produce 900 rpm with constant T load
Ns = 4.5 t
Interpole
RIP 0.005 W
Load
T= constant
Ra
Rs
0.0023 W
Rx
???? W
0.0172 W
Rf
Ea
49.2 W
Shunt Field
n1 = 850 rpm
Use the value of
Bp2 computed from
the previous part.
Series Field
Nf = 577 t
240 V
VT
B p2 0.83 T
R f 49.2 W
Use the magnetizing curve from the text find the total mmf required to
product the computed flux density.
12
Slide 13
Lesson 20 332a.pptx
EXAMPLE 20-1 SOLUTION (9)
Number of turns in each field winding
N f 577 t
Motor Magnetizing Curve
Shunt
1.2
f net
N s 4.5 t
I a21 477.2 A
Current computed
from the previous
part.
F lu x D e n s ity (T )
Series
1000
1
.83
0.8
0.6
0.4
0.2
0
0
1
2
3
4
5
6
7
mmf (in 1000 A-t/pole)
Fnet = 4000 A-t
13
Slide 14
Lesson 20 332a.pptx
EXAMPLE 20-1 SOLUTION (10)
4000 A-t/pole
Answer e.)
14
Slide 15
Lesson 20 332a.pptx
ET 332a
Dc Motors, Generators and Energy Conversion Devices
END LESSON 20
15
Lesson 20 332a.pptx
ET 332a
Dc Motors, Generators and Energy Conversion Devices
LESSON 20: NON-LINEAR OPERATION OF
COMPOUND MOTORS
1
Slide 2
Lesson 20 332a.pptx
LEARNING OBJECTIVES
After this presentation you will be able to:
Determine the operating point of a dc compound motor
Observe the effect of driving a constant torque load on
motor performance
Compute the value of field resistance to produce a
given speed
Solve non-linear dc motor problems given a
magnetization curve.
2
Slide 3
Lesson 20 332a.pptx
NON-LINEAR COMPOUND MOTOR
CALCULATIONS
Example 20-1: Compound motor with non-linear magnetic circuit. Ten
percent of series field used to offset armature reaction.
240 V, 125 HP, 850 rpm, Ra = 0.0172 ohms RIP = 0.005 ohms
Series field resistance Rs = 0.0023 ohms
Shunt field resistance Rf = 49.2 ohms
Series field turns Ns = 4.5 t
Shunt field turns Nf = 577 t
Efficiency at rated load 85.4%
Drives a constant torque load
Compute a.) If b.) Ia c.) developed torque d.) Ia when a series R is
added to increase speed to 900 rpm. e.) The field resistance in series
with the shunt coil to produce the 900 rpm speed.
3
Slide 4
Lesson 20 332a.pptx
EXAMPLE 20-1 SOLUTION (1)
Ns = 4.5 t
Interpole
RIP 0.005 W
Load
T= constant
Ra
Series Field
Magnetization
curve given in
figure 11-7 in text
Rs
0.0023 W
???? W
Rx
0.0172 W
Rf
49.2 W
Ea
240 V
VT
Shunt Field
n1 = 850 rpm
Nf = 577 t
Answer a.)
Find Ia from rated output power and
efficiency
4
Slide 5
Lesson 20 332a.pptx
EXAMPLE 20-1 SOLUTION (2)
Answer b.)
5
Slide 6
Lesson 20 332a.pptx
EXAMPLE 20-1 SOLUTION (3)
Answer c.)
6
Slide 7
Lesson 20 332a.pptx
EXAMPLE 20-1 SOLUTION (4)
Part d.) Ia2 = ??? Use Fig 11-7 to find the total field mmf.
Motor Magnetizing Curve
1.2
f net
F lu x D e n sity (T )
.88
1000
1
0.8
0.6
0.4
0.2
0
0
1
2
3
4
5
6
7
mmf (in 1000 A-t/pole)
7
Slide 8
Lesson 20 332a.pptx
EXAMPLE 20-1 SOLUTION (5)
For non-linear operation, torque in proportional to Bp∙Ia
For constant torque load, TD1 = TD2
Solve for Ia2
This relates Ia2 to Bp2
Need another equation
8
Slide 9
Lesson 20 332a.pptx
EXAMPLE 20-1 SOLUTION (6)
Use speeds n1= 850 rpm n2=900 rpm. Speed is inversely proportional to
Bp.
Speed
Ratio
9
Slide 10
Lesson 20 332a.pptx
EXAMPLE 20-1 SOLUTION (7)
10
Slide 11
Lesson 20 332a.pptx
EXAMPLE 20-1 SOLUTION (7)
Solve the quadratic equation using the quadratic formula
11
Slide 12
Lesson 20 332a.pptx
EXAMPLE 20-1 SOLUTION (8)
Part e.) Find the value of Rx to produce 900 rpm with constant T load
Ns = 4.5 t
Interpole
RIP 0.005 W
Load
T= constant
Ra
Rs
0.0023 W
Rx
???? W
0.0172 W
Rf
Ea
49.2 W
Shunt Field
n1 = 850 rpm
Use the value of
Bp2 computed from
the previous part.
Series Field
Nf = 577 t
240 V
VT
B p2 0.83 T
R f 49.2 W
Use the magnetizing curve from the text find the total mmf required to
product the computed flux density.
12
Slide 13
Lesson 20 332a.pptx
EXAMPLE 20-1 SOLUTION (9)
Number of turns in each field winding
N f 577 t
Motor Magnetizing Curve
Shunt
1.2
f net
N s 4.5 t
I a21 477.2 A
Current computed
from the previous
part.
F lu x D e n s ity (T )
Series
1000
1
.83
0.8
0.6
0.4
0.2
0
0
1
2
3
4
5
6
7
mmf (in 1000 A-t/pole)
Fnet = 4000 A-t
13
Slide 14
Lesson 20 332a.pptx
EXAMPLE 20-1 SOLUTION (10)
4000 A-t/pole
Answer e.)
14
Slide 15
Lesson 20 332a.pptx
ET 332a
Dc Motors, Generators and Energy Conversion Devices
END LESSON 20
15