Reg No.:

00000EE409121902

Pages: 2

Name:

APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY

Seventh Semester B.Tech Degree Examination (Regular and Supplementary), December 2020

Max. Marks: 100

+> ~ WN

10 a)

0)

11

Course Code: EE409

Course Name: Electrical Machine Design

PARTA
Answer all questions, each carries 5 marks.
What considerations impose limitations in design of electrical machines?
Distinguish between power transformers and distribution transformers.

Explain the procedure for designing the shunt field winding for a DC machine.

What are the factors to be considered for the design of field winding in a
synchronous machine?

What are the guiding factors for the choice of number of armature slots in a
three-phase induction machine?

What are the criteria for the choice of number of slots of an induction machine?

What are the advantages of FEM based methods over conventional design
methods?
Compare the analysis method and synthesis method of machine design.
PART 13

Answer any two full questions, each carries 10 marks.
The temperature rise of a transformer is 25°C after 1 hour and 37.5°C after 2
hours of starting from cold conditions. Calculate its final steady temperature rise
and the heating time constant. If its temperature falls from the final steady state
value to 40°C in 1.5 hours when disconnected, calculate the cooling time
constant. The ambient temperature is 30°C.
What are the practical aspects of unbalanced magnetic pull that must be
considered while designing electrical machines?
A 200 KVA, 6600/440 V50Hz,3 phase core type transformer has the following
design data. Maximum flux density = 1.3 wb/m?, emf per turn =10V, stacking
factor=0.9, window space factor=0.3, current density= 2.5 A/mm’, overall
width= overall height, 3 stepped core is used. Calculate the overall dimensions
of the transformer.
A 250KVA, 6600/400 V, 3 phase core type transformer has a total loss of 4800
W at full load. The transformer tank is 1.25 m in height and 1mx0.5m in plan.
Design a suitable scheme for the tubes if the average temperature rise is to be
limited to 35°C. The diameter of the tube is 50mm and is spaced 75mm from
each other.The average height of the tube is 1.05m. Specific heat dissipation due

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Duration: 3 Hours

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