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APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
Third Semester B.Tech - November,2025
Course Code PCEET303 Max. Marks 60
DC MACHINES & 2 hour 30
Course Name Duration
TRANSFORMERS minutes
PART A - Short Answer Questions (Answer All)
Q.
Question Marks
No.
1 What is the necessity of starters in DC motors? 4
2 Explain any three methods of electric braking in DC shunt motor. 4
3 Explain the different speed control methods of DC motors. 4
Explain the speed vs armature current and torque characteristics of a DC series
4 4
motor.
5 Explain the significance of back emf in DC motors. 3
6 Derive the electromagnetic torque equation of a DC machine. 5
7 Explain armature reaction in DC generator. How its effects can be minimized. 4
8 Explain with neat sketches, the process of commutation in DC machines. 4
PART B - Descriptive Questions (Answer any ONE from each module)
Q.
Part Question Marks
No.
Module 1
(a) Explain armature reaction in DC generator and list effects. 7
1
(b) Explain how the effects of armature reaction can be minimized. 8
(a) Explain the process of commutation in DC machines with neat sketches. 7
2
(b) Describe any two methods to improve commutation. 8
Module 2
(a) Explain field control method of DC motors. 7
3
(b) Explain armature control method of DC motors. 8
APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
Third Semester B.Tech - November,2025
Course Code PCEET303 Max. Marks 60
DC MACHINES & 2 hour 30
Course Name Duration
TRANSFORMERS minutes
PART A - Short Answer Questions (Answer All)
Q.
Question Marks
No.
1 What is the necessity of starters in DC motors? 4
2 Explain any three methods of electric braking in DC shunt motor. 4
3 Explain the different speed control methods of DC motors. 4
Explain the speed vs armature current and torque characteristics of a DC series
4 4
motor.
5 Explain the significance of back emf in DC motors. 3
6 Derive the electromagnetic torque equation of a DC machine. 5
7 Explain armature reaction in DC generator. How its effects can be minimized. 4
8 Explain with neat sketches, the process of commutation in DC machines. 4
PART B - Descriptive Questions (Answer any ONE from each module)
Q.
Part Question Marks
No.
Module 1
(a) Explain armature reaction in DC generator and list effects. 7
1
(b) Explain how the effects of armature reaction can be minimized. 8
(a) Explain the process of commutation in DC machines with neat sketches. 7
2
(b) Describe any two methods to improve commutation. 8
Module 2
(a) Explain field control method of DC motors. 7
3
(b) Explain armature control method of DC motors. 8
