E G192102 Pages:2

Reg No.:_. Name:

APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
SEVENTH SEMESTER B.TECH DEGREE EXAMINATION(R&S), DECEMBER 2019

Course Code: EE409

Course Name: Electrical Machine Design

Max. Marks: 100 Duration: 3 Hours
PARTA
Answer all questions, each carries 5 marks. Marks
1 Briefly explain the different types of enclosures used in electrical machines. (5)
2 Give two differences between power transformer and distribution transformer. (5)
3 Explain in steps the design of series field winding fora DC machine. (5)
4 Salient pole alternators are not suitable for high speeds. Why? (5)
5 State and explain the factors considered for selection of air gap length in (5)

induction motors.
6 List and justify the advantages of a larger air gap in induction motor. (5)
List out and explain the features of three finite element based softwares for (5)

analysis of electrical machines.

8 Explain the basic concept of computer aided design. (5)
PART 1
Answer any two full questions, each carries 10 marks.
9 Explain the procedure to calculate MMF for air gap and teeth in an electrical (10)
machine.

10 a) Write the design equations to find the area of cross section of conductor for both (3)

primary and secondary of a transformer.
b) Determine the dimensions of core and window for ೩ 5kVA, 50117, single phase (7)

core type transformer. A rectangular core is used with long side twice as long as
short side. The window height is three times the width. Volt per turn is 1.8V,
window space factor is 0.2, current density is 1.8A/mm? and maximum flux
density is 1Wb/m?.

11 a) A 151:۷۷ 230۷ 4 pole ‏عل‎ machine has the following data. (7)
Armature diameter 0.25m, armature core length 0.125m, length of air gap at pole
centre 2.5mm, flux per pole 11.7 mWb, Ratio of pole arc to pole pitch 0.66.
Calculate the mmf required for air gap if (1) armature surface is treated as

smooth (ii) armature is slotted and the gap contraction factor is 1.18.

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