Exam Details
| Subject | electrical machine-iii | |
| Paper | ||
| Exam / Course | pddc | |
| Department | ||
| Organization | Gujarat Technological University | |
| Position | ||
| Exam Date | May, 2017 | |
| City, State | gujarat, ahmedabad |
Question Paper
1
Seat No.: Enrolment
GUJARAT TECHNOLOGICAL UNIVERSITY
PDDC SEMESTER VI- EXAMINATION SUMMER 2017
Subject Code: X60901 Date: 29/04/2017
Subject Name: Electrical Machine-III
Time: 10.30AM to 01.00PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1
Explain slip test for determining Xd and Xq of salient pole synchronous machine. Draw circuit diagram.
07
Explain constructional features of alternator. Also explain its types and corresponding application fields for alternators.
07
Q.2
Explain hunting of synchronous machines and methods of its prevention.
07
Explain coil span factor and distribution factor of an alternator.
07
OR
Derive e.m.f. equation of alternator. Explain distribution factor with effect of harmonics.
07
Q.3
Explain Hopkinson's test for determination of efficiency of DC shunt machine.
07
What are the advantages of connecting alternators in parallel? Draw circuit diagram for one dark and two bright lamp method.
07
OR
Q.3
Explain an experimental method of determining curve for a synchronous motor.
07
Following data is obtained when two DC shunt machines were tested by Hopkinson's test:
Supply voltage 230 Supply current 2.6 Current taken from generating machine 4.5 Field current of generator 0.5 Field current of motor 0.4A, Ra 2 Calculate efficiency for machine working as a motor.
07
Q.4
Explain working principle and construction of AC servomotor.
07
A 2 MVA, 3-phase, 8 pole alternator is connected to 6000 50 Hz bus bar and has synchronous reactance of 4 Ω/ph. Find synchronizing power and torque per mechanical degree of rotor displacement at no load. Consider normal excitation condition.
07
OR
Q.4
Explain the construction and working principle of a reluctance motor.
07
What is voltage regulation of alternator? Explain MMF method to find voltage regulation of alternator.
07
Q.5
What synchronous motor is not self start? Explain the methods of starting of synchronous motor.
07
Explain construction and working of PMBLDC motor.
07
OR
Q.5
What are the causes of harmonics in the voltage waveforms of an alternator? How they can be minimized?
07
Explain the Brake test on DC machine.
07
Seat No.: Enrolment
GUJARAT TECHNOLOGICAL UNIVERSITY
PDDC SEMESTER VI- EXAMINATION SUMMER 2017
Subject Code: X60901 Date: 29/04/2017
Subject Name: Electrical Machine-III
Time: 10.30AM to 01.00PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1
Explain slip test for determining Xd and Xq of salient pole synchronous machine. Draw circuit diagram.
07
Explain constructional features of alternator. Also explain its types and corresponding application fields for alternators.
07
Q.2
Explain hunting of synchronous machines and methods of its prevention.
07
Explain coil span factor and distribution factor of an alternator.
07
OR
Derive e.m.f. equation of alternator. Explain distribution factor with effect of harmonics.
07
Q.3
Explain Hopkinson's test for determination of efficiency of DC shunt machine.
07
What are the advantages of connecting alternators in parallel? Draw circuit diagram for one dark and two bright lamp method.
07
OR
Q.3
Explain an experimental method of determining curve for a synchronous motor.
07
Following data is obtained when two DC shunt machines were tested by Hopkinson's test:
Supply voltage 230 Supply current 2.6 Current taken from generating machine 4.5 Field current of generator 0.5 Field current of motor 0.4A, Ra 2 Calculate efficiency for machine working as a motor.
07
Q.4
Explain working principle and construction of AC servomotor.
07
A 2 MVA, 3-phase, 8 pole alternator is connected to 6000 50 Hz bus bar and has synchronous reactance of 4 Ω/ph. Find synchronizing power and torque per mechanical degree of rotor displacement at no load. Consider normal excitation condition.
07
OR
Q.4
Explain the construction and working principle of a reluctance motor.
07
What is voltage regulation of alternator? Explain MMF method to find voltage regulation of alternator.
07
Q.5
What synchronous motor is not self start? Explain the methods of starting of synchronous motor.
07
Explain construction and working of PMBLDC motor.
07
OR
Q.5
What are the causes of harmonics in the voltage waveforms of an alternator? How they can be minimized?
07
Explain the Brake test on DC machine.
07
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