# 28633 - Electrotechnics T-A (A-K)

• Campus: Bologna
• Corso: First cycle degree programme (L) in Engineering Management (cod. 0925)

## Learning outcomes

Expand and develope of concepts and methodologies relating steady-state and quasi steady-state electromagnetism. Provide the main tools for the analysis of electric and magnetic circuits. Illustration of the construction and operation of the main electrical machinery and components of an electric power system.

## Course contents

Requirements/Prior knowledge

A basic knowledge of electromagnetisms is required. This knowledge is usually acquired passing the exam of General Physics T-B. The student should also have achieved a good knowledge of the fundamentals of differential and integral calculation from the Mathematical Analysis courses.

All lectures will be held in Italian. It is therefore necessary to understand the Italian language to profitably attend the course and be able to use the educational material provided.

Programme

Basic concepts

Lumped parameter circuits. Circuit elements. Voltage and current.
Power and energy. Sign conventions. Passive and active elements.
Kirchhoff's laws. From field theory to circuit theory.

Resistors. Independent voltage and current sources. Series and parallel circuits. Current and voltage dividers. Source transformations. Millman's formula.
Resistive two-port elements: R and G parameters, hybrid parameters, transmission parameters, relationship between parameters, wye-delta transformation, dependent sources, ideal transformer.
Analisys methods: tableau analysis, node-voltage and mesh-current methods.
Network theorems: Tellegen's theorem, superposition principle, Thévenin's and Norton's theorems, reciprocity theorem.

Transient analysis

First order RC and RL circuits. Initial conditions. Transient and steady state response. Zero input and zero state response. Second order RLC circuits (general information).

Capacitors. Inductors. Coupled inductors.
Phasors. Impedance and admittance. Circuit analysis with phasors and complex impedances.
Power in AC circuits: active, reactive, and apparent power. Complex power. Effective (RMS) values. Power factor correction. Maximum power transfer.
Frequency response. Transfer function. Resonance.

Three-phase systems

Three-phase systems. Wye and delta connected loads. Power in three-phase systems. Three-phase systems with neutral wire.

Magnetic circuits

Magnetic properties of materials. Diamagnetic, paramagnetic and ferromagnetic materials. magnetic circuits. Reluctance. Hopkinson’s law.

Transformers

Operational principle. Field hypothesis. Internal and external equations. Equivalent circuits. No-load and short circuit conditions. Efficiency measurement.

Asynchronous machines.

Operational principle. Field hypothesis. Internal and external equations. Equivalence theorem. Equivalent circuit. Mechanical and electromechanical characteristics.

Synchronous machines.

Operational principle. Internal and external equations.

Electrical power systems and electrical safety

Electric power generation, transmission and distribution. Protection against unintended connections. Protections against over-currents and over-voltages.

For further study, students can consider the following books:

G. Rizzoni, J. Kearns, Principles and Applications of Electrical engineering, McGraw-Hill

C. Alexander, M. Sadiku, Electric Circuits, McGraw-Hill

A. R. Hambley, Electrical Engineering: Principles and Applications, Pearso

J. Edminister, M. Nahvi, Electric Circuits, Schaum (McGraw-Hill)

## Teaching methods

The course takes place in the first period of the second year of the first cycle degree course in "Ingegneria Gestionale", and consists of 6 credits corresponding to 60 hours of lectures, during which the teacher will explain in classroom the topics covered in the program. About 40 hours will be devoted to the theoretical development of the fundamental concepts and methodologies of electrical engineering. The remaining 20 hours will be devoted to exercises, during which the student, using the theoretical notions developed, will acquire the practical skills necessary to analyze electrical circuits in steady state, transient and sinusoidal regime, as well as three-phase systems and magnetic configurations.

## Assessment methods

The exam aims at assessing the student mastery of the basic concepts in electrical engineering.

During the examination the student must demonstrate the knowledge of the fundamentals which enable to apply the electromagnetic theory to the study of the most common applications of electrical engineering (electrical circuits, electric power systems, electric machines).

The student must also demonstrate his ability in solving independently simple illustrative problems, applying the methods developed during the course.

The student can pass the exam in one of the following ways:

Partial tests: the student will take two partial tests, the first one at the middle of the course period, and the second one at the course period end. During each test a theoretical question, regarding one of the topics covered in class, and two exercises will be administered to the students.

The student has 20 minutes to answer the theoretical question, producing a short written text, where he will be expected to demonstrate the achievement of a comprehensive vision of the proposed theme, the mastery of specific technical language and his ability to synthesis and analysis. During this phase, the student is not allowed to use hand calculators, textbooks and lecture notes.

The student has then 120 minutes to solve the two proposed exercises. During the first partial test, the exercises will focus on the study of electrical circuits in steady state and transient regimes. The exercises of the second partial test will instead focus on the study of circuits in sinusoidal regime, three-phase systems and magnetic circuits. The student must demonstrate to properly apply the analytical methods developed during the course and to have achieved a critical sensitivity to the results obtained. During this phase, the student is allowed to use a hand calculator, as well as textbooks and lecture notes.

At the end of the two partial tests two average scores will be issued, one for the exercises and one for the answers to the questions. A total score will be calculated as a weighted average of the two previous scores. The exam is passed if both scores are above or equal to 18/30. In this case, the total score will be registered. If one or both scores (for the exercises and for the answers to the questions) are not sufficient, but the total score is greater or equal to 14/30, the student is allowed to take an oral integrative examination within the winter session.

Comprehensive examination: students can register to one of the exams published on the AlmaEsami [https://almaesami.unibo.it/almaesami/welcome.htm] system. The comprehensive examination consists of a written and an oral test. The written test consists of two exercises, aimed at verifying that the student is able to correctly apply the analysis methods developed during the course and that he has acquired a critical sensitivity to the obtained results. The student has 120 minutes to solve the exercises, which will focus on the study of electrical circuits in transient and sinusoidal regimes, three-phase systems and magnetic circuits. The student is allowed to use a hand calculator, as well as textbooks and lecture notes.

A minimum score of 14/30 is required to access the oral exam phase. The score remains valid during the entire session in which the written test has been taken. Partecipating and delivering a written test will cancel the score obtained in any previous test.

The student must take the oral test in the same session in which he passed the written test. During the oral examination, the student is invited to discuss some of the topics taught during the course. The discussion is aimed at assessing whether the student has achieved an organic view of the proposed topic, a good grasp of the specific technical language and adequate capacity for synthesis and analysis.

The degree of satisfaction of the above mentioned requirements contribute to the formulation of the final score, together with the mark obtained in the written test.

## Teaching tools

Further educational material can be found on Insegnamenti OnLine [https://virtuale.unibo.it/]

## Office hours

See the website of Leonardo Sandrolini

### SDGs

This teaching activity contributes to the achievement of the Sustainable Development Goals of the UN 2030 Agenda.