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APJ ABDUL KALAM TECHNOLOGICAL UNIVERSITY
THIRD SEMESTER B.TECH DEGREE EXAMINATION(S), MAY 2019

Course Code: EE205
Course Name: DC MACHINES AND TRANSFORMERS
PARTA
Answer all questions, each carries5 marks.

Name the parts of dc machine and state the functions of any two parts.
Derive the emf equation of dc generator.
With the help of speed-armature current characteristics, explain why the series
motors should not be started without any load.

Why the rating of transformer in kVA?

List out the necessary and desirable conditions for parallel operation of two
single phase transformers.
Define all day efficiency. How this efficiency of a transformer varies with load?
A 10 kVA, 1500/150 V, single phase transformer has following parameters:
HV side: 71 = 4.20 x, = 5.14 LVside: 12 = 0.05 2 = 0.0622 0
the per unit values of equivalent resistance and inductive reactance.
What is the purpose of tertiary winding in three winding transformer?
PART छ

Answer any two full questions, each carries10 marks.
Draw the winding diagram of a dc machine with 4 poles, 12 slots progressive
double layer lap winding.
Name the different losses occur in dc machine. How the magnetic losses are
minimized in 00 machine?
A 4 pole wave connected armature of a de generator has 120 conductors and runs
at 1200 rpm. If the flux per pole is 0.015 Wb, find the emf generated. Keeping
the flux constant, suggest a change in the armature of the generator so that the
generator is capable to generate half of the no load voltage when running at the
same speed.
What is self excitation? What are the conditions for building up of voltage in 60
shunt generator?

A 10 KW shunt generator having resistances1Q and 10062, delivers full load at a

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Duration: 3 Hours

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