Exam Details
| Subject | electrical machine design i and ii | |
| 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 VIII- EXAMINATION SUMMER 2017
Subject Code: X80902 Date: 01/05/2017
Subject Name: Electrical Machine Design I and II
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
Which are the losses occurring in transformer? Derive condition for maximum efficiency.
07
Explain how following factors affect the main dimensions of a d.c. machine.
ratio,
Peripharal speed,
Moment of inertia,
07
Q.2
Derive relation Et= k√Q, kVA rating of a transformer. Discuss significance of the value of k.
07
Discuss design procedure to design a commutator and brushes of a d.c. machine.
07
OR
Determine main dimensions of 50 kW, 4 pole 600 rpm, dc shunt generator with full load terminal voltage 220 V. The maximum gap flux density is 0.83 wb/m2. And specific electric loading is 30000.
Assume that full load armature voltage drop is of rated terminal voltage and field current is of rated full load current. Ratio of pole arc to pole pitch is 0.67 and pole face is square.
07
Q.3
Discuss process of calculating no load current for a three phase transformer from design data.
07
What is Dispersion coefficient? Explain the effect of Dispersion coefficient on maximum output power factor.
07
OR
Q.3
Discuss factors to be considered while selecting number of poles in the design of d.c. machine.
07
Discuss the effect of "skewing" on the performance of three phase induction motor.
07
Q.4
Calculate main dimension of stator no. of stator slots and winding turns per phase for a 22.5 kw 3 ph. 440 V 960 rpm 50 hz, delta connected induction motor for overall good electrical design. Assume ac/m 25000 Bav 0.46T, p.f. 0.87 and peripheral velocity should not exceed 30 m/sec
14
OR
Q.4
Discuss factors affecting the length of air gap on performance of a three phase induction motor.
07
Explain which combinations of number of stator and rotor slots should be avoided in the induction motor design why?
07
2
Q.5
Discuss the effect of SCR in the design of synchronous machine..
07
Explain the terms "critical speed" and "run away speed" with reference to synchronous machine.
07
OR
Q.5
Write technical note on classification of insulating materials.
07
Write steps and necessary equations for rotor design of a synchronous machine.
07
Seat No.: Enrolment
GUJARAT TECHNOLOGICAL UNIVERSITY
PDDC SEMESTER VIII- EXAMINATION SUMMER 2017
Subject Code: X80902 Date: 01/05/2017
Subject Name: Electrical Machine Design I and II
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
Which are the losses occurring in transformer? Derive condition for maximum efficiency.
07
Explain how following factors affect the main dimensions of a d.c. machine.
ratio,
Peripharal speed,
Moment of inertia,
07
Q.2
Derive relation Et= k√Q, kVA rating of a transformer. Discuss significance of the value of k.
07
Discuss design procedure to design a commutator and brushes of a d.c. machine.
07
OR
Determine main dimensions of 50 kW, 4 pole 600 rpm, dc shunt generator with full load terminal voltage 220 V. The maximum gap flux density is 0.83 wb/m2. And specific electric loading is 30000.
Assume that full load armature voltage drop is of rated terminal voltage and field current is of rated full load current. Ratio of pole arc to pole pitch is 0.67 and pole face is square.
07
Q.3
Discuss process of calculating no load current for a three phase transformer from design data.
07
What is Dispersion coefficient? Explain the effect of Dispersion coefficient on maximum output power factor.
07
OR
Q.3
Discuss factors to be considered while selecting number of poles in the design of d.c. machine.
07
Discuss the effect of "skewing" on the performance of three phase induction motor.
07
Q.4
Calculate main dimension of stator no. of stator slots and winding turns per phase for a 22.5 kw 3 ph. 440 V 960 rpm 50 hz, delta connected induction motor for overall good electrical design. Assume ac/m 25000 Bav 0.46T, p.f. 0.87 and peripheral velocity should not exceed 30 m/sec
14
OR
Q.4
Discuss factors affecting the length of air gap on performance of a three phase induction motor.
07
Explain which combinations of number of stator and rotor slots should be avoided in the induction motor design why?
07
2
Q.5
Discuss the effect of SCR in the design of synchronous machine..
07
Explain the terms "critical speed" and "run away speed" with reference to synchronous machine.
07
OR
Q.5
Write technical note on classification of insulating materials.
07
Write steps and necessary equations for rotor design of a synchronous machine.
07
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