E 10000EE409122005 Pages: 2

Reg No.: Name:
APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY

Seventh Semester B.Tech Degree Regular and Supplementary Examination December 2021 (2015 Scheme)

Course Code: EE409
Course Name: Electrical Machine Design

Max. Marks: 100 Duration: 3 Hours
PARTA
Answer all questions, each carries 5 marks. Marks
1 What are the practical aspects of unbalanced magnetic pull? (5)
2 Derive the output equation of a single phase transformer. (5)
3 Explain the types of specific loadings used for the design of DC machines. (5)
4 The output coefficient of 1250kVA,300 rpm, synchronous generator is 200.The (5)

ratio of length to the diameter is 0.2.Calculate the main dimensions if the
specific loadings are decreased by 20 % with speed remaining constant.
5 Distinguish between slip ring and squirrel cage induction motor (5)
6 What are the guiding factors used for the selection of number of stator slotsin3 (5)

phase induction motors?

7 Explain the historical background of finite element method? (5)
8 With the help of a flow chart, explain the analysis method of design of CAD (5)
PART B

Answer any two full questions, each carries 10 marks.

9 Explain any 5 types of enclosures used in electrical machines. (10)
10 a) A DC motor has final temperature rise of 80 °C and a heating time constant of (5)

75 minutes. Estimate at this load, the temperature rise after 1 hour

b) Explain the different types of cooling methods used for dry type transformers. (5)

11 a) The ratio of full load mmf in a 400kVA,50 hz ,single phase core type (5)

transformer is 2.4 x 10~°.Calculate the net iron area and full load mmf of the

transformer. Maximum flux density in the core is 1.3 wb/m?,current density is

2.7 A/mm? and the window space factor =0.26.

b) Differentiate between power transformer and distribution transformer (5)

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