Exam Details
| Subject | synchronous and induction machines (ee) | |
| Paper | ||
| Exam / Course | b.tech | |
| Department | ||
| Organization | Government Degree College, Kamalpur | |
| Position | ||
| Exam Date | July, 2017 | |
| City, State | tripura, dhalai |
Question Paper
B B4B0102
Page 1 of 2
Total Pages: 2
Reg
APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
FOURTH SEMESTER B.TECH DEGREE EXAMINATION, JULY 2017
Course Code: EE202
Course Name: SYNCHRONOUS AND INDUCTION MACHINES
Max. Marks: 100 Duration: 3 Hours
PART A
Answer all questions. Each carries 5 marks.
1 Enumerate various methods for minimising harmonics in alternators.
2 What are the different methods of finding the voltage regulation of an alternator.
3 Describe the slip test method for finding the Xd and Xq of synchronous machines.
4 Explain the constructional details of a synchronous motor.
5 Differentiate between the phenomenon cogging and crawling of an induction
motor.
6 List the various methods adopted for braking of an induction motor.
7 Compare induction generator with synchronous generator.
8 With a sketch describe the principle of working of a shaded pole motor.
PART B
Answer any two questions. Each carries 10 marks.
9 Explain various types of armature winding of an alternator.
Find the distribution and pitch factor of a 4 pole, 24 slots alternator having its
armature coils short pitched by one slot.
10 A 0.5 MVA, 1.1KV, 50 Hz, star connected alternator has Ra and Xs per phase
as 0.1Ω and 1.5Ω respectively. Find its voltage regulation at different power factor
of unity 0.9 lag and 0.8 lead at full load.
11 A 220V, 6 pole, 50 Hz, star connected alternator gave the following test results:
Field current
in A
0.2 0.4 0.6 0.8 1 1.2 1.4 1.8 2.2 2.6 3 3.4
Open circuit
line voltage in
Volts
29 58 87 116 146 172 194 232 261 284 300 310
ZPF test line
voltage in
volts
0 29 88 140 177 208 230
SCC in A 6.6 13.2 20 26.5 32.4 40 46.3 59
Find voltage regulation at full load current of 40A at power factor 0.8 lag by
m.m.f method (ii)ZPF method. Ra=0.06 Ω /phase.
B B4B0102
Page 2 of 2
PART C
Answer any two questions. Each carries 10 marks.
12 Explain the two reaction theory of salient pole alternator.
13 Describe the constructional features of slip ring induction motor.
A 6 pole, 50 Hz, slip ring induction motor, the rotor resistance and the reactance
at stand still per phase are 0.3 and 1.5 Ω respectively. The e.m.f between the slip
rings on open circuit is 175V. Calculate Slip rotor e.m.f/phase rotor
frequency and reactance when the motor runs at a speed of 950 r.p.m.
14 What are the various methods of synchronisation of alternators.
Explain the effect of excitation on armature current and power factor of a
synchronous motor and hence deduce the V and inverted V curves.
PART D
Answer any two questions. Each carries 10 marks.
15 What are the different types of starters used for starting a induction motor.
A induction motor has a short circuit current 5 times of full load current at
slip. Determine the starting torque and starting current if the impressed voltage is
reduced to 60% of the normal voltage by using starting resistance starter. The full
load current and torque are 10 A and 10 Nm respectively.
16 Explain the principle of operation of an induction generator.
Describe the double field revolving theory of a 1 induction motor.
17 Draw the circle diagram of a 20 hp,400V,50Hz star connected induction motor
with the following test data:
No load test 400V 9A cos
block rotor test 200V 50A cos
Stator and rotor copper losses are divided equally in the block rotor test.
From the above circle diagram obtain line current power factor slip
efficiency at full load.
Page 1 of 2
Total Pages: 2
Reg
APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
FOURTH SEMESTER B.TECH DEGREE EXAMINATION, JULY 2017
Course Code: EE202
Course Name: SYNCHRONOUS AND INDUCTION MACHINES
Max. Marks: 100 Duration: 3 Hours
PART A
Answer all questions. Each carries 5 marks.
1 Enumerate various methods for minimising harmonics in alternators.
2 What are the different methods of finding the voltage regulation of an alternator.
3 Describe the slip test method for finding the Xd and Xq of synchronous machines.
4 Explain the constructional details of a synchronous motor.
5 Differentiate between the phenomenon cogging and crawling of an induction
motor.
6 List the various methods adopted for braking of an induction motor.
7 Compare induction generator with synchronous generator.
8 With a sketch describe the principle of working of a shaded pole motor.
PART B
Answer any two questions. Each carries 10 marks.
9 Explain various types of armature winding of an alternator.
Find the distribution and pitch factor of a 4 pole, 24 slots alternator having its
armature coils short pitched by one slot.
10 A 0.5 MVA, 1.1KV, 50 Hz, star connected alternator has Ra and Xs per phase
as 0.1Ω and 1.5Ω respectively. Find its voltage regulation at different power factor
of unity 0.9 lag and 0.8 lead at full load.
11 A 220V, 6 pole, 50 Hz, star connected alternator gave the following test results:
Field current
in A
0.2 0.4 0.6 0.8 1 1.2 1.4 1.8 2.2 2.6 3 3.4
Open circuit
line voltage in
Volts
29 58 87 116 146 172 194 232 261 284 300 310
ZPF test line
voltage in
volts
0 29 88 140 177 208 230
SCC in A 6.6 13.2 20 26.5 32.4 40 46.3 59
Find voltage regulation at full load current of 40A at power factor 0.8 lag by
m.m.f method (ii)ZPF method. Ra=0.06 Ω /phase.
B B4B0102
Page 2 of 2
PART C
Answer any two questions. Each carries 10 marks.
12 Explain the two reaction theory of salient pole alternator.
13 Describe the constructional features of slip ring induction motor.
A 6 pole, 50 Hz, slip ring induction motor, the rotor resistance and the reactance
at stand still per phase are 0.3 and 1.5 Ω respectively. The e.m.f between the slip
rings on open circuit is 175V. Calculate Slip rotor e.m.f/phase rotor
frequency and reactance when the motor runs at a speed of 950 r.p.m.
14 What are the various methods of synchronisation of alternators.
Explain the effect of excitation on armature current and power factor of a
synchronous motor and hence deduce the V and inverted V curves.
PART D
Answer any two questions. Each carries 10 marks.
15 What are the different types of starters used for starting a induction motor.
A induction motor has a short circuit current 5 times of full load current at
slip. Determine the starting torque and starting current if the impressed voltage is
reduced to 60% of the normal voltage by using starting resistance starter. The full
load current and torque are 10 A and 10 Nm respectively.
16 Explain the principle of operation of an induction generator.
Describe the double field revolving theory of a 1 induction motor.
17 Draw the circle diagram of a 20 hp,400V,50Hz star connected induction motor
with the following test data:
No load test 400V 9A cos
block rotor test 200V 50A cos
Stator and rotor copper losses are divided equally in the block rotor test.
From the above circle diagram obtain line current power factor slip
efficiency at full load.
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