# Mid-Term Exam - I

```Kingdom of Saudi Arabia
Ministry of Higher Education
Majmaah University
College of Engineering
Department: Electrical Engineering
Exam Information
Course code:
Instructor:
Section number:
Exam time:
Exam hall:
Number of pages:
First Exam
EE 398
Course Title: Electrical Machines
Dr.Praveen R.P.
850
Exam date:
10-11-2014
From:
10.00 am
To:
12.00 pm
3D 39
4
Total score:
20 points
Student’s Information
Name:
ID:
Exam Instructions:
 Read the questions carefully and several times. Writing clearly will make
 Any form of cheating, intention to cheating, or disruption of the exam will
subject you to a disciplinary action as specified by the university’s
regulations.
 Carrying or using the mobile phone during the exam is not allowed. Using
the phone during the exam will carry a disciplinary action.
 The calculator is only permitted by the exam supervisor.
 No student can leave the exam room during the first half hour of the
exam. Any student coming after the first half hour of the exam will not be
permitted to enter the exam.
 A student leaving the exam, even for legitimate reasons, may not be given
a makeup exam.
Points Earned:
Question
1
2
3
Score
Question
4
5
6
Score
Total score in the exam:
Dear student, we encourage you to answer the exam the best you can and we
wish you all success.
Q1. Explain the principle of operation of a Transformer ?
Q2. Derive the emf equation of a transformer ?
(3 marks)
(5 marks)
Q3. An ideal 25 KVA transformer has 500 turns on the primary winding and 40 turns
on the secondary winding. The primary is connected to 3000 V, 50 Hz supply.
Calculate (i) primary and secondary currents on full load (ii) secondary e.m.f and
(iii) the maximum core flux ?
(5 marks)
Q4. Draw the no-load phasor diagram of a transformer and hence explain what is
working component (Iw) and magnetizing components (I&micro;) of no-load current ?
(3 marks)
Q5.
Derive the simplified equivalent circuit of a Transformer from the exact
equivalent circuit?
(4 marks)
```