29247 - Electrical Machines T

Learning outcomes

The course is proposed to supply the basic knowledge for the study of the widely used electric machines. The operating principles and the performance in different operating conditions will be analysed. After passing this course, students will be familiar with issues involved in electromechanical energy conversion, use of mathematical models to predict the machine behaviour, analysis of usual operating conditions.

Course contents

Prerequisites

Basic skills in mathematics, physics and electrical engineering.

 

Course contents

Introduction

Main properties of conducting, dielectric and ferromagnetic materials employed in electrical machines. Losses and heat dissipation.

 

Transformers

Single phase transformers: principle of operation, simplified mathematical model, eddy current losses in the core, mathematical model with eddy current losses, mathematical model with eddy current losses and core saturation, equivalent circuit referred to primary and referred to secondary, no load operating conditions, load operating conditions, rated operating conditions, transformer tests, transformer losses, parallel operation of transformers, structure, heat dissipation, measurement transformers, autotransformers.

Three-phase transformers: winding connections, mathematical model, equivalent circuit, structure, no load operating conditions, behavior with unbalanced loads, transformer tests, parallel operations, auto transformers.

 

DC machines

Introduction, magnetic circuit, field winding, armature winding, brushes and commutator, armature reaction, electromagnetic torque, mathematical model, commutation process, interpoles, compensating windings, circuit connections, torque/speed curves, permanent magnet DC machines.

 

Synchronous machines

Introduction, classification, principle of operation. Synchronous machines with round rotor: magnetic circuit, stator and rotor windings, analysis of the air-gap magnetic field, mathematical model under sinusoidal operating conditions, synchronous reactance, Behn-Eschemburg vectorial diagram, electromagnetic torque. Synchronous machines with salient pole rotor: magnetic circuit, mathematical model under sinusoidal operating conditions, synchronous reactances, Arnold-Blondel vectorial diagram, electromagnetic torque. Steady-state and dynamic stability limits, swing oscillations, damping windings. Grid connection of a synchronous generator. Introduction to permanent magnet synchronous machines.

 

Induction machines

Introduction, classification, principle of operation, magnetic circuit, stator and rotor windings, analysis of the air-gap magnetic field, slip, mathematical model under sinusoidal operating conditions, equivalent circuit, electromagnetic torque, torque/speed curve, induction machines with cage rotor, starting and speed regulation. Single-phase induction machines: principle of operation, mathematical model, equivalent circuit, starting problems.

Readings/Bibliography

It is not necessary to buy specific books. The pdf files of the slides utilized during the lessons are indispensable and sufficient for the preparation for the exam, and are available on VIRTUALE (https://virtuale.unibo.it/). For further considerations:

Title: Conversione elettrica ed elettromeccanica dell’energia
Authors: B. Brunelli
Editor: Pitagora (Bologna)

Title: Macchine elettriche
Authors: A. E. Fitzgerald, C. Kingsley, A. Kusko
Editor: Franco Angeli

Title: Costruzioni elettromeccaniche (Vol. I e II)
Authors: E. Di Pierro
Editor: Edizioni Scientifiche Siderea (Roma)

Title: Macchine elettriche
Authors: L. Fusco, D. Iannuzzi, E. Pagano, L. Piegari
Editor: Liguori Editori (Napoli)

Title: Electrical machines (Vol. I e II)
Authors: M. Kostenko, l. Piotrovsky
Editor: Mir Publishers (Moscow)

Title: The nature of polyphase induction machines
Authors: P. L. Alger
Editor: John Wiley and Sons (New York)

Teaching methods

The frontal lessons in the classroom are supported by computer-based exercises, which are also conducted in the classroom (MATLAB-Simulink, FEMM). During these exercises, students will be able to analyze the electromagnetic behavior of electric machines in detail.

Assessment methods

The exam consists of an oral examination with a final grade, based on a discussion of four topics from the course. One of the topics is chosen by the student.

 

During the oral exam, students will be required to demonstrate a solid understanding of the theoretical principles and fundamental concepts governing the operation of various types of electrical machines, as well as the ability to apply them effectively to the analysis and interpretation of relevant physical and engineering phenomena. The evaluation will prioritize critical mastery of the topics, the ability to connect the various aspects of the discipline, and the appropriate use of technical and scientific language. Preparation limited to the mere rote memorization of facts, without an actual understanding of the concepts and their practical implications, will be considered insufficient for passing the exam.

 

Calculators and reference materials are not permitted. The use of AI is prohibited. Any use constitutes a violation of academic integrity. There are no midterm exams, and no assignments are required.

 

Students with specific learning disorders (SLD) or temporary/permanent disabilities.

We recommend contacting the University Office responsible for support services in a timely manner (https://site.unibo.it/studenti-con-disabilita-e-dsa/it) [https://site.unibo.it/studenti-con-disabilita-e-dsa/it):] . The office will evaluate the students' needs and, where appropriate, propose possible accommodations. These must in any case be submitted for approval at least 15 days in advance to the course instructor, who will assess their suitability also in relation to the learning objectives of the course.

Teaching tools

Lessons are carried out using a computer and a projector (PowerPoint). PDF files of the PowerPoint slides shown during the course, as well as the Simulink and FEMM models used during the in-class exercises, are available on the VIRTUALE platform (https://virtuale.unibo.it/).

Office hours

See the website of Angelo Tani