Download GTU B.Tech 2020 Winter 7th Sem 2170909 Design Of Ac Machines Question Paper

Download GTU (Gujarat Technological University Ahmedabad) B.Tech/BE (Bachelor of Technology/ Bachelor of Engineering) 2020 Winter 7th Sem 2170909 Design Of Ac Machines Previous Question Paper

Seat No.: ________
Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE- SEMESTER?VII (NEW) EXAMINATION ? WINTER 2020
Subject Code:2170909 Date:30/01/2021
Subject Name:Design of AC Machines
Time:10:30 AM TO 12:30 PM Total Marks: 47
Instructions:
1. Attempt any THREE questions from Q.1 to Q.6.
2. Q7 is compulsory.

3. Make suitable assumptions wherever necessary.

4. Figures to the right indicate full marks.

Q.1 (a) Explain factors to be considered for selecting specific magnetic loading 03
for 3- phase I. M.

(b) Sketch the different types of rotor slot in 3 phase I. M..
04

(c) What is dispersion coefficient? How does it affect maximum power? 07


fa
ctor
Q.2 (a) What is the role of damper winding in synchronous generator and motor?
03

(b) Explain step for designing the field winding of Synchronous machine.
04

(c) A 1250 kVA, 3 phase, 50 Hz, 3300 V, 300 rpm, synchronous generator 07
with a concentric winding has the following design data: specific magnetic
loading, Bav = 0.58 Wb/m2, specific electrical loading, ac = 33000 A/m,
gap length = 5.5 mm, field turn per pole = 60, winding factor = 0.955, short
circuit ratio = 1.2, The effective gap area is 0.6 times the actual area.
Peripheral speed is 30 m/s. Find stator core length, stator bore, turns per
phase, mmf for air gap, armature mmf per pole and filed current for no
load and rated voltage.







Q.3 (a) Which factors affecting the size of 3-phase induction motor? Explain in 03
short.

(b) Briefly discuss factors affecting determining air gap length in induction 04
motor design.

(c) Which types of slots are used for stator? How the number of slots is 07
estimated? Which point are to be considered for selecting number of
stator slots?




Q.4 (a) State and explain the factor to be considered for selecting specific 03
electrical loading for 3 phase I. M..

(b) State the rules for the selection of rotor slots in 3-phase squirrel cage
04
induction motor.

(c) List out the method for reducing harmonics in induction motor? Explain 07
in brief.
Q.5 (a) Explain direct axis and quadrature axis synchronous reactance in 03
synchronous machine.

(b) Explain how mmf is calculated for magnetic circuit in synchronous 04
machine.

(c) Explain design of damper winding with equation.
07
1

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Q.6 (a) Explain the terms "peripheral speed" & "run-away speed" with reference 03
to synchronous machine

(b) State the important design different between turbo alternators and hydro 04
generators.

(c) What is SCR? Discuss its effect in synchronous machine performance.
07



Q.7 (a) Explain application of FEM technique for design problems.
05


OR
Q.7 (a) State the procedure of designing an auxiliary winding in case of resistance 05
spilt phase motor.
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2

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