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Reg. No. Name:

B3D048S Pages: 3

APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
THIRD SEMESTER B.TECH DEGREE EXAMINATION, JULY 2017

Course Code: EE205
Course Name: DC MACHINES AND TRANSFORMERS (EE)

Max. Marks: 100 Duration: 3 Hours
PARTA
Answer all questions.
1. Compare lap and wave windings used for DC machine armature (5)
2. Draw the magnetization characteristic of self excited DC shunt generator and explain.

10.

(5)
How back emf is generated in ೩ DC motor? Explain its significance. (5)
Draw and explain the detailed phasor diagram of a practical transformer supplying
lagging power factor load. (5)
Define all-day efficiency of a transformer. What is done to improve the all-day
efficiency of a distribution transformer? (5)
List out and explain the necessary and desirable conditions for parallel operation of
transformers. (5)
Enumerate the purposes which dictate the use of tertiary winding in a three winding
transformer. (5)
Draw the diagram for V-V connection of transformers and explain the voltage and
current relations of line and phase values. Derive the capacity ratio as a fraction of
A-A capacity. (5)

PART B
Answer any 2 questions.

a. Derive the electro-dynamic equation of rotating electrical machines and explain the
principle of energy conversion. (5)
b. Draw the developed winding layout of a lap connected simplex double layer DC
armature with 16 slots and 4 poles. Furnish the winding table and show connections to
4 equalizer rings. (5)
a. Derive the EMF equation of a DC generator, from first principles (5)
b. A shunt generator delivers 195 A at a terminal voltage of 250 V. The armature and

shunt field resistances are 0.02 Q and 50 Q respectively. The iron and frictional losses

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