JNTU Kakinada B-Tech 4-2 SPECIAL ELECTRICAL MACHINES R13 April 2018 Question Paper

IV B.Tech II Semester Regular/Supplementary Examinations, April – 2018
SPECIAL ELECTRICAL MACHINES (Electrical and Electronics Engineering)Time: 3 hours Max. Marks: 70
Question paper consists of Part-A and Part-B
Answer ALL sub questions from Part-A
Answer any THREE questions from Part-B
*****

PART ?A (22 Marks)1. a) Why the number of stator and rotor poles are not same in Switched Reluctance
motors? Explain.
[4]
b) Differentiate between Stepper motors and Switched Reluctance motors. [4]
c) Compare between permanent magnets and electro magnets. [4]
d) What is a BLDC motor? Mention their advantages. [4]
e) Explain the principle of linear induction motor. [3]
f) List the motors used in electric traction. [3]

PART ?B (3×16 = 48 Marks)2. a) Discuss the merits of Switched Reluctance motors compared to induction
motors.
[8]
b) Explain the torque production mechanism in Switched Reluctance motors. [8]

3. a) List and discuss different types and applications of stepper motors. [8]
b) Define the terms with respect to a stepper motor: stator pole pitch, rotor pole
pitch and step angle.
[4]
c) For a three-phase 12/8 VR stepper motor, calculate stator pole pitch, rotor pole
pitch and full step angle.
[4]

4. What are the advantages of PM DC machines? Draw and explain the
constructional details of a permanent magnet DC machine.
[16]

5. a) What is a commutator? What is its need in electrical machines? Compare
between mechanical and electronic commutators.
[8]
b) Prove that the PM BLDC machines have 15% more power density than the
PMSM.
[8]

6. What are linear motors? Explain different types and applications of linear
motors.
[16]

7. a) Discuss the main characteristics of traction drives. [8]
b) Discuss the application of Linear Induction Motors for electric traction. [8]
Code No: RT42022C
Set No. 1
R13
1 of 1

IV B.Tech II Semester Regular/Supplementary Examinations, April – 2018
SPECIAL ELECTRICAL MACHINES (Electrical and Electronics Engineering)Time: 3 hours Max. Marks: 70
Question paper consists of Part-A and Part-B
Answer ALL sub questions from Part-A
Answer any THREE questions from Part-B
*****

PART ?A (22 Marks)1. a) Why the number of stator and rotor poles are not same in Switched Reluctance
motors? Explain.
[4]
b) Differentiate between Stepper motors and Switched Reluctance motors. [4]
c) Compare between permanent magnets and electro magnets. [4]
d) What is a BLDC motor? Mention their advantages. [4]
e) Explain the principle of linear induction motor. [3]
f) List the motors used in electric traction. [3]

PART ?B (3×16 = 48 Marks)2. a) Discuss the merits of Switched Reluctance motors compared to induction
motors.
[8]
b) Explain the torque production mechanism in Switched Reluctance motors. [8]

3. a) List and discuss different types and applications of stepper motors. [8]
b) Define the terms with respect to a stepper motor: stator pole pitch, rotor pole
pitch and step angle.
[4]
c) For a three-phase 12/8 VR stepper motor, calculate stator pole pitch, rotor pole
pitch and full step angle.
[4]

4. What are the advantages of PM DC machines? Draw and explain the
constructional details of a permanent magnet DC machine.
[16]

5. a) What is a commutator? What is its need in electrical machines? Compare
between mechanical and electronic commutators.
[8]
b) Prove that the PM BLDC machines have 15% more power density than the
PMSM.
[8]

6. What are linear motors? Explain different types and applications of linear
motors.
[16]

7. a) Discuss the main characteristics of traction drives. [8]
b) Discuss the application of Linear Induction Motors for electric traction. [8]
Code No: RT42022C
Set No. 1
R13
1 of 1

IV B.Tech II Semester Regular/Supplementary Examinations, April – 2018
SPECIAL ELECTRICAL MACHINES (Electrical and Electronics Engineering)Time: 3 hours Max. Marks: 70
Question paper consists of Part-A and Part-B
Answer ALL sub questions from Part-A
Answer any THREE questions from Part-B
*****

PART ?A (22 Marks)1. a) Define the term Reluctance. Also derive the relation between reluctance and
inductance.
[4]
b) Define step angle of a Stepper motor. For a three-phase 12/8 VR stepper motor,
calculate step angle.
[4]
c) Discuss the advantages of permanent magnet DC motor over conventional DC
motors.
[4]
d) Compare between BLDC motor and PMSM. [4]
e) List the applications of linear induction motors. [3]
f) Why DC series motor is better suitable for traction than DC shunt motor? [3]

PART ?B (3×16 = 48 Marks)2. What is the need for power converter in the operation of Switched Reluctance
motors? Explain any two power converters for a three-phase, 6/4 Switched
Reluctance motor.

[16]
3. a) With a block diagram, explain the open loop control of a stepper motor. [8]
b) Explain the torque production in variable reluctance stepper motors. [8]

4. a) What is a PMDC motor? Explain its working. [8]
b) Derive the expression for torque of a PMDC motor. [8]

5. What are the merits of brushless DC motors? With a neat block diagram,
explain the closed loop control of a BLDC motor.
[16]
6. a) Compare between Linear synchronous motor and Linear Induction motor. [8]
b) Explain the working of linear induction motor. [8]

7. a) Compare between DC traction and AC traction. [8]
b) A train driven by separately excited dc motors has better co-efficient of
adhesion than driven by series motor. Justify the statement. Draw the simplified
speed/time curve for the main line services and show all necessary periods.

[8]

Code No: RT42022C
Set No. 2
R13
1 of 1

IV B.Tech II Semester Regular/Supplementary Examinations, April – 2018
SPECIAL ELECTRICAL MACHINES (Electrical and Electronics Engineering)Time: 3 hours Max. Marks: 70
Question paper consists of Part-A and Part-B
Answer ALL sub questions from Part-A
Answer any THREE questions from Part-B
*****

PART ?A (22 Marks)1. a) Why the number of stator and rotor poles are not same in Switched Reluctance
motors? Explain.
[4]
b) Differentiate between Stepper motors and Switched Reluctance motors. [4]
c) Compare between permanent magnets and electro magnets. [4]
d) What is a BLDC motor? Mention their advantages. [4]
e) Explain the principle of linear induction motor. [3]
f) List the motors used in electric traction. [3]

PART ?B (3×16 = 48 Marks)2. a) Discuss the merits of Switched Reluctance motors compared to induction
motors.
[8]
b) Explain the torque production mechanism in Switched Reluctance motors. [8]

3. a) List and discuss different types and applications of stepper motors. [8]
b) Define the terms with respect to a stepper motor: stator pole pitch, rotor pole
pitch and step angle.
[4]
c) For a three-phase 12/8 VR stepper motor, calculate stator pole pitch, rotor pole
pitch and full step angle.
[4]

4. What are the advantages of PM DC machines? Draw and explain the
constructional details of a permanent magnet DC machine.
[16]

5. a) What is a commutator? What is its need in electrical machines? Compare
between mechanical and electronic commutators.
[8]
b) Prove that the PM BLDC machines have 15% more power density than the
PMSM.
[8]

6. What are linear motors? Explain different types and applications of linear
motors.
[16]

7. a) Discuss the main characteristics of traction drives. [8]
b) Discuss the application of Linear Induction Motors for electric traction. [8]
Code No: RT42022C
Set No. 1
R13
1 of 1

IV B.Tech II Semester Regular/Supplementary Examinations, April – 2018
SPECIAL ELECTRICAL MACHINES (Electrical and Electronics Engineering)Time: 3 hours Max. Marks: 70
Question paper consists of Part-A and Part-B
Answer ALL sub questions from Part-A
Answer any THREE questions from Part-B
*****

PART ?A (22 Marks)1. a) Define the term Reluctance. Also derive the relation between reluctance and
inductance.
[4]
b) Define step angle of a Stepper motor. For a three-phase 12/8 VR stepper motor,
calculate step angle.
[4]
c) Discuss the advantages of permanent magnet DC motor over conventional DC
motors.
[4]
d) Compare between BLDC motor and PMSM. [4]
e) List the applications of linear induction motors. [3]
f) Why DC series motor is better suitable for traction than DC shunt motor? [3]

PART ?B (3×16 = 48 Marks)2. What is the need for power converter in the operation of Switched Reluctance
motors? Explain any two power converters for a three-phase, 6/4 Switched
Reluctance motor.

[16]
3. a) With a block diagram, explain the open loop control of a stepper motor. [8]
b) Explain the torque production in variable reluctance stepper motors. [8]

4. a) What is a PMDC motor? Explain its working. [8]
b) Derive the expression for torque of a PMDC motor. [8]

5. What are the merits of brushless DC motors? With a neat block diagram,
explain the closed loop control of a BLDC motor.
[16]
6. a) Compare between Linear synchronous motor and Linear Induction motor. [8]
b) Explain the working of linear induction motor. [8]

7. a) Compare between DC traction and AC traction. [8]
b) A train driven by separately excited dc motors has better co-efficient of
adhesion than driven by series motor. Justify the statement. Draw the simplified
speed/time curve for the main line services and show all necessary periods.

[8]

Code No: RT42022C
Set No. 2
R13
1 of 1

IV B.Tech II Semester Regular/Supplementary Examinations, April – 2018
SPECIAL ELECTRICAL MACHINES (Electrical and Electronics Engineering)Time: 3 hours Max. Marks: 70
Question paper consists of Part-A and Part-B
Answer ALL sub questions from Part-A
Answer any THREE questions from Part-B
*****

PART ?A (22 Marks)1. a) List the advantages and applications od Switched Reluctance Motors. [4]
b) What are the differences between a Stepper motor and a Servo motor? [4]
c) List the main limitations of permanent magnet machines. [4]
d) Write the shape of back EMFs of a BLDC motor. [3]
e) Define and explain Goodness factor. [4]
f) What are the advantages of electric traction? [3]

PART ?B (3×16 = 48 Marks)2. a) What is the need for rotor position sensor in the control of Switched Reluctance
motors? Explain the working of hall sensors.
[8]
b) Explain the control of Switched Reluctance motor using asymmetric power
converter.
[8]

3. a) What are Hybrid stepper motors? Explain their working. [8]
b) Compare between open loop and closed loop control of stepper motors. [8]

4. a) What is a PMDC motor? Draw and explain its equivalent circuit. [8]
b) Discuss the advantages and applications of PM DC motors. [8]

5. a) Compare between BLDC motors and PMSMs. [8]
b) Discuss the advantages and applications of BLDC motors. [8]

6. With a neat diagram, explain the construction of linear synchronous motor.
Also list their applications.
[16]

7. a) Discuss different supply systems used in electric traction. [8]
b) Draw and explain a typical Speed ?Time curve for train movement. [8]

Code No: RT42022C
Set No. 3
R13
1 of 1

IV B.Tech II Semester Regular/Supplementary Examinations, April – 2018
SPECIAL ELECTRICAL MACHINES (Electrical and Electronics Engineering)Time: 3 hours Max. Marks: 70
Question paper consists of Part-A and Part-B
Answer ALL sub questions from Part-A
Answer any THREE questions from Part-B
*****

PART ?A (22 Marks)1. a) Why the number of stator and rotor poles are not same in Switched Reluctance
motors? Explain.
[4]
b) Differentiate between Stepper motors and Switched Reluctance motors. [4]
c) Compare between permanent magnets and electro magnets. [4]
d) What is a BLDC motor? Mention their advantages. [4]
e) Explain the principle of linear induction motor. [3]
f) List the motors used in electric traction. [3]

PART ?B (3×16 = 48 Marks)2. a) Discuss the merits of Switched Reluctance motors compared to induction
motors.
[8]
b) Explain the torque production mechanism in Switched Reluctance motors. [8]

3. a) List and discuss different types and applications of stepper motors. [8]
b) Define the terms with respect to a stepper motor: stator pole pitch, rotor pole
pitch and step angle.
[4]
c) For a three-phase 12/8 VR stepper motor, calculate stator pole pitch, rotor pole
pitch and full step angle.
[4]

4. What are the advantages of PM DC machines? Draw and explain the
constructional details of a permanent magnet DC machine.
[16]

5. a) What is a commutator? What is its need in electrical machines? Compare
between mechanical and electronic commutators.
[8]
b) Prove that the PM BLDC machines have 15% more power density than the
PMSM.
[8]

6. What are linear motors? Explain different types and applications of linear
motors.
[16]

7. a) Discuss the main characteristics of traction drives. [8]
b) Discuss the application of Linear Induction Motors for electric traction. [8]
Code No: RT42022C
Set No. 1
R13
1 of 1

IV B.Tech II Semester Regular/Supplementary Examinations, April – 2018
SPECIAL ELECTRICAL MACHINES (Electrical and Electronics Engineering)Time: 3 hours Max. Marks: 70
Question paper consists of Part-A and Part-B
Answer ALL sub questions from Part-A
Answer any THREE questions from Part-B
*****

PART ?A (22 Marks)1. a) Define the term Reluctance. Also derive the relation between reluctance and
inductance.
[4]
b) Define step angle of a Stepper motor. For a three-phase 12/8 VR stepper motor,
calculate step angle.
[4]
c) Discuss the advantages of permanent magnet DC motor over conventional DC
motors.
[4]
d) Compare between BLDC motor and PMSM. [4]
e) List the applications of linear induction motors. [3]
f) Why DC series motor is better suitable for traction than DC shunt motor? [3]

PART ?B (3×16 = 48 Marks)2. What is the need for power converter in the operation of Switched Reluctance
motors? Explain any two power converters for a three-phase, 6/4 Switched
Reluctance motor.

[16]
3. a) With a block diagram, explain the open loop control of a stepper motor. [8]
b) Explain the torque production in variable reluctance stepper motors. [8]

4. a) What is a PMDC motor? Explain its working. [8]
b) Derive the expression for torque of a PMDC motor. [8]

5. What are the merits of brushless DC motors? With a neat block diagram,
explain the closed loop control of a BLDC motor.
[16]
6. a) Compare between Linear synchronous motor and Linear Induction motor. [8]
b) Explain the working of linear induction motor. [8]

7. a) Compare between DC traction and AC traction. [8]
b) A train driven by separately excited dc motors has better co-efficient of
adhesion than driven by series motor. Justify the statement. Draw the simplified
speed/time curve for the main line services and show all necessary periods.

[8]

Code No: RT42022C
Set No. 2
R13
1 of 1

IV B.Tech II Semester Regular/Supplementary Examinations, April – 2018
SPECIAL ELECTRICAL MACHINES (Electrical and Electronics Engineering)Time: 3 hours Max. Marks: 70
Question paper consists of Part-A and Part-B
Answer ALL sub questions from Part-A
Answer any THREE questions from Part-B
*****

PART ?A (22 Marks)1. a) List the advantages and applications od Switched Reluctance Motors. [4]
b) What are the differences between a Stepper motor and a Servo motor? [4]
c) List the main limitations of permanent magnet machines. [4]
d) Write the shape of back EMFs of a BLDC motor. [3]
e) Define and explain Goodness factor. [4]
f) What are the advantages of electric traction? [3]

PART ?B (3×16 = 48 Marks)2. a) What is the need for rotor position sensor in the control of Switched Reluctance
motors? Explain the working of hall sensors.
[8]
b) Explain the control of Switched Reluctance motor using asymmetric power
converter.
[8]

3. a) What are Hybrid stepper motors? Explain their working. [8]
b) Compare between open loop and closed loop control of stepper motors. [8]

4. a) What is a PMDC motor? Draw and explain its equivalent circuit. [8]
b) Discuss the advantages and applications of PM DC motors. [8]

5. a) Compare between BLDC motors and PMSMs. [8]
b) Discuss the advantages and applications of BLDC motors. [8]

6. With a neat diagram, explain the construction of linear synchronous motor.
Also list their applications.
[16]

7. a) Discuss different supply systems used in electric traction. [8]
b) Draw and explain a typical Speed ?Time curve for train movement. [8]

Code No: RT42022C
Set No. 3
R13
1 of 1

IV B.Tech II Semester Regular/Supplementary Examinations, April – 2018
SPECIAL ELECTRICAL MACHINES (Electrical and Electronics Engineering)Time: 3 hours Max. Marks: 70
Question paper consists of Part-A and Part-B
Answer ALL sub questions from Part-A
Answer any THREE questions from Part-B
*****

PART ?A (22 Marks)1. a) Explain the operating principle of Switched Reluctance Motors. [4]
b) List and discuss the applications of Stepper motors. [4]
c) List the applications of PMDC motors. [4]
d) What is the need for position sensor in BLDC motor? [4]
e) List different types of Linear motors. [3]
f) What are the motors used in electric traction? [3]

PART ?B (3×16 = 48 Marks)2. a) Draw and discuss the shape of phase inductance of a Switched Reluctance
motor with respect to rotor position.
[8]
b) List and discuss various advantages and applications of Switched Reluctance
motors.
[8]

3. a) With a neat diagram, explain the constructional details of a variable reluctance
stepper motor.
[8]
b) Explain torque production in stepper motor. What is the effect of hybrid
stepping in the torque production?
[8]

4. a) What are moving coil motors? Explain its working and list their applications. [8]
b) What are electromagnets? Discuss the advantages and disadvantages of
permanent magnets over electromagnets.
[8]

5. a) Draw and discuss the back emf waveforms of a three phase BLDC motor. [6]
b) With a neat schematic diagram, explain the sensorless control of a three phase
BLDC motor.
[10]

6. Discuss the construction, principle of operation and various applications of liner
induction motor.
[16]

7. What are tractions drives? Explain the use of single sided linear induction motor
for traction drives.
[16]

Code No: RT42022C
Set No. 4
R13
1 of 1