Transilvania University of Brasov
Faculty of Electrical Engineering and Computers


SUBJECT LIST
for the Engineer Degree Diploma Exam 2007 at the subject:
ELECTRICAL ENGINEERING AND CONTROL SYSTEMS
Study programme: Electrical Engineering and Computers (English language)

A. ELECTRICAL ENGINEERING

A1) Electromagnetics
A number of 5 subjects will be arbitrarily selected from the list below:

1.

Components of the electric field strength in large sense, with the mention of the cause that
produces each of them.
2.

Difference between the turn magnetic flux and the flux linked by a coil.
3.

Definition of the vector electric polarization in terms of the electric moment of a multipol or an
equivalent dipol. The explanatory drawing. Specify the denomination and the unit of measure
for each quantity occurring in expression.
4.

The work done by the forces of a potential electric field at the displacement of a point-like
electric charge between two points. Explanatory drawing, mathematical expressions,
denomination and unit of measure of each quantity occurring in formula.
5.

Magnetic circuital law in integral form. Specify:
a.

What represent the lower limits of the integrals (closed curve, open curve, closed surface,
open surface, volume)
b.

Explanatory drawing and specify if the directions of travelling along the curve and of the
normal to the surface bounded by the curve are adopted arbitrarily or not, and in which
manner.
c.

Denomination of each occurring quantity.
6.

Relation between the tangential components of the electric field strength when passing from a
medium to another. On what is based the derivation of this relation (enunciation without proof),
explanatory drawing, unit of measure.
7.

Relation between the normal components of the electric induction when passing from a medium
to another. On what is based the derivation of this relation (enunciation without proof),
explanatory drawing, unit of measure.
8.

Relation between the normal components of the magnetic induction when passing from a
medium to another. On what is based the derivation of this relation (enunciation without proof),
explanatory drawing, unit of measure.
9.

Relation between the tangential component of the magnetic field strength when passing from a
medium to another. On what is based the derivation of this relation (enunciation without proof),
explanatory drawing, unit of measure.
10.

Draw a magnetic hysteresis loop. Precise the characteristic points and their denomination, and
fix approximately on the loop the operating point given by H and B in the air gap.
11.

Law of electromagnetic induction in concentrated integral form, for media at rest, and in the
form with global quantities (without integrals), i.e. the form referred to as Faraday form.
Explanatory drawing, denomination and unit of measure for each occurring quantity. Precise if
the occurring surfaces are closed, open or anyhow.
12.

Biot-Savart-Laplace theorem. Explanatory drawing, denomination and unit of measure of each
quantity occurring in formula.
13.

Unit of measure of the electric field strength. The defining relation, explanatory drawing,
denomination of occurring quantities. 14.

Unit of measure of the electric tension. Defining relation, explanatory drawing, denomination of
occurring quantities.
15.

Unit of measure of the magnetic field strength. Defining relation, explanatory drawing,
denomination of occurring quantities.
16.

Unit of measure of magnetic induction. Defining relation, explanatory drawing, denomination of
occurring quantities.
17.

Unit of measure of the magnetic flux. Defining relation, explanatory drawing, denomination of
occurring quantities.
18.

Unit of measure of the intensity of the electric current from the definition of electric current in
terms of the passing electric charge quantity. Defining relation, explanatory drawing,
denomination of occurring quantities.
19.

Lenz rule. Explanatory figure. Enunciation.
20.

Eddy currents in a metallic plate at rest in a variable magnetic field. Explanations without proof.
21.

What is an electrostatic screen? Explanatory drawing. Does this screen act in both direction with
respect to external charges and internal charges or not?
22.

Definition of inductances.
23.

Example of positive and negative inductances considering coils wound about the same toroidal
core (without proof). Meaning of the dot introduced at one end of the coil.
24.

Hopkinson law for magnetic circuits.
25.

Definition of capacitance. What does it mean a capacitor?

Bibliography
Nicolaide, A.: Electromagnetics, Transilvania University Press, Braov, 2003.


A2) Electric Circuits
A number of 5 subjects will be arbitrarily selected from the list below:

1.

The relationship between instantaneous voltage
( )
t
u
c
and current
( )
t
i
in a capacitor.
2.

The energy stored on a capacitor
3.

The inductance of a coil
4.

The relationship between instantaneous voltage
( )
t
u
L
and current
( )
t
i
in an inductor
5.

The energy stored in an inductor
6.

Millmans theorem
7.

Thevenins theorem
8.

Nortons theorem
9.

The maximum power transfer theorem
10.

The power conservation theorem
11.

The time constant of a series RL circuit
12.

The time constant of a series RC circuit
13.

The root-mean-squre (r.m.s.) of an electric current
14.

The root-mean-squre (r.m.s.) of a sinusoidal quantity
15.

The angular frequency
16.

The phasor representation of a sinusoidal quantity
17.

Jouberts theorem
18.

Powers under sinusoidal conditions
19.

Power factor
20.

The relations between the line and phase values of the currents and voltages in the case of wye
and delta connection
21.

Powers absorbed by a three-phase load
22.

Symmetrical components (Fortescue transformation)
23.

The frequency spectrum 24.

The root-mean-squre (r.m.s.) of a periodic non-sinusoidal quantity
25.

Powers under non-sinusoidal conditions


Bibliography
Nicolaide, A.: Lecture notes, 2004.


B. CONTROL SYSTEMS

B1) Electrical machines
A number of 2 subjects will be arbitrarily selected from the list below:

1.

Single-phase non-ideal transformer. Theory of operation based on equations.
2.

Single-phase non-ideal transformer. To express the turn ratio, voltage regulation and the
maximum efficiency criterion.
3.

Single-phase non-ideal transformer. Equivalent diagrams for open circuit and short circuit tests
to determine its parameters.
4.

Three-phase transformer. Theory and diagrams of basic connections schemes.
5.

Direct Current machine: explanatory figure for magnetization characteristic of a DC machine.
6.

The expressions of developed torque and of losses structure for a DC motor.
7.

To express relations of power and torque for an induction motor.
8.

The equivalent circuit of an induction motor. The significance of parameters.
9.

Induction motor, torque - speed characteristics. Explanatory diagrams.
10.

Field orientated control of induction motor: Principle, Clarke and Park diagrams.

Bibliography
1.

Guru, Bhag S. and Hiziroglu.R.H.: Electric Machinery and Transformers, 3-rd edition,
Hardback, 720 pages, July 2000, ISBN 13 9780195138900, OXFORD University Press
2.

Ilea, D: Lecture Notes, 2005.

B2) Electrical drives
A number of 2 subjects will be arbitrarily selected from the list below:

1
Using the Laplace-transformation applied to the differential equations of the separately
excited DC machine with constant excitation, compute the step response to set point
changes (i.e. the speed variations of the DC machine if the armature voltage changes).
2
Write the voltage equations and the torque equation in the two-axis rotating system for the
salient-pole synchronous machine. Assume the machine is operating in steady-state
operation at mains power supply; translate these equations into the complex plane and then
draw the phasor diagram.
Select and then prove the relation that matches to the following sentence:
The speed variation to set-point changes of the armature voltage of the separately excited
DC machine is oscillating if:
3.
a.
1
T
4
T
D
A
m
< =

b.
1
T
4
T
D
A
m
> =

4.
Induction (asynchronous) machine in field oriented coordinate system: field oriented
operation; the rotor equations in field oriented coordinates; control strategy diagram;
analogy to DC machines structure diagram. I. Choose the correct answer:
The torque of some synchronous machines is composed of two components: the
synchronous torque and the reluctance torque. The reluctance torque:
a. appears in cylindrical-rotor machines and is depending on the excitation;
b. results from the difference of the permeances on the magnetic axes of the machine;
c. appears both in cylindrical-rotor and salient-pole synchronous machines but doesn't
depend on excitation.
a:
b:
c:
5.
II. Somewhere into the following sentence some mistakes have been filled-in. Locate and
then correct them.
The direct and quadrature axis theory approach is as follows:
1. Torque invariant transformation of both three-phase (rotor and stator) to two phase
systems;
2. Transformation of the steady rotor winding and rotating rotor winding to an arbitrary
system, rotating with angular velocity;
3. Setting up the voltage equations for rotor and stator in the transformed system;
4. Determination of the voltages from balance of power.
6.
Step-by-step motors: what are step-by-step motors;