LAGOS CITY POLYTECHNIC, IKEJA
SCHOOL OF ENGINEERING AND APPLIED SCIENCE
DEPARTMENT OF ELECT/ELECT ENGINEERING
2015/2016 SEMESTER EXAMINATION
COURSE TITLE:
COURSE CODE:
FOR WHOM:
ANSWER
ELECTRICAL MACHINES II
EEC 233
ND YR II
EE
ANY
NO OF QUESTIONS :
6
TIME ALLOWED: 2 HRS
PT
INSTRUCTIONS:
4
QUESTIONS
1.
(a)
(b)
(c)
Explain
the
principle
of
operation
of
a
transformer
Differentiate between Ideal transformer & practical Transformer.
With the aid of an Equivalent circuit diagram, describe a practical transformer.
2.
(a)
Differentiate between shell Type transformer from Core type transformer.
(b)
Draw the phasor diagram of a single phase transformer on Lead and No-Load
respectively.
(c)
Mention
3
methods
of
cooling
transformers.
3.
(a)
(b)
(c)
State
the
principle
of
Induction
What
are
electromagnets?
Differentiate between synchronous generators from synchronous motors.
4.
(a)
Mention and briefly explain the 3 common methods of cooling transformers.
(b)
With the aid of a block diagram, describe the linked energy of an
electromechanical
machine.
(c)
Give three causes of heat dissipation in an electromechanical system.
5.
(a)
(b)
(c)
State
the
energy
balance
equation
Mention
any
4
method
of
testing
transformers
Draw the connection diagram of three single phase transformers for three phase
operation
in
star
connection
arrangement.
(a)
(b)
value of
moving
Explain
the
parallel
operation
of
three
phase
transformers
A 2 pole generator has a magnetic flux of 10mwb per pole; calculate the average
the emf generated in one of the armature conductors while it is
through
the
magnetic flux of one pole, if the armature is driven at 600r.p.m
Illustrate with a schematic diagram, the principle of induction from a primary to a
secondary circuit.
6.
(c)