40042 - Electric Drives for industrial and Wind Energy Applications

Learning outcomes

At the end of the course, the student knows: - the general methodologies to understand the performance and control of electrical machines and drives - the fundamentals of the electrical machines, from circuit behavior to electromagnetic torque production, and the basic equations of the physical phenomena - the mathematical models of electrical machines, which are valid for steady-state and transient analysis - how to model and simulate dc motor drives, permanent magnet brushless motor drives, induction motor drives, and stepper motors. Also, the course focuses on the fundamentals of electric generators and drives for wind energy systems, which are used as examples of applications.

Course contents

The course provides the fundamental tools needed to understand the structure, operating principles and control methods of the main electrical drives, with particular reference to applications in electrical energy systems and automation. The course also introduces the principles of electromechanical energy conversion and the main issues related to the selection, sizing and use of electrical machines in real applications.

Basic knowledge of electrical engineering, electric circuits and three-phase electrical systems is required.

The course is organized into three main parts:

Part I – Theoretical foundations
Study of the structure, characteristics and operating principles of the main electrical machines and related drives.

Part II – Laboratory activities
Practical implementation and experimental analysis of the main drives studied during the lectures.

The topics covered are listed below.

• Introduction to electrical machines and drives

General concepts on electrical machines and electrical drives. Review of basic electrical engineering. Magnetic and conductive materials. Magnetic circuits. Principles of electromechanical energy conversion. Heat dissipation. Space vectors and phasors.

• Drives for DC machines

Geometry and operating principle of DC machines. Torque expression, equivalent circuit and mechanical characteristic. Motor and generator operation. Torque and speed control. Field weakening and constant-torque and constant-power operating regions. Control techniques and dedicated drives.

• Drives for three-phase synchronous machines and sinusoidal back-EMF brushless motors

Machine geometry and rotating magnetic field. Torque expression, equivalent circuit and mechanical characteristic. Dynamic model based on quadrature-axis theory. Field-Oriented Control, FOC. Limit performance in terms of torque and speed.

• Drives for brushless motors with trapezoidal back-EMF

Structure and operating principle. Phase supply sequences and their relationship with rotor position. Six-step operation with two phases supplied at a time. Switching transients and torque oscillations. Block diagram of the drive.

• Drives for three-phase induction machines

Geometry, operating principle, torque production and mechanical characteristics. Starting issues. Scalar V/f control. Constant-torque and constant-power operating regions. Dynamic model based on quadrature-axis theory. Vector control and rotor flux estimation. Direct and indirect torque control methods. Limit performance.

• Single-phase induction motors

Structure and operating principles. Main types of single-phase induction motors: capacitor-start, capacitor-start and run, permanent split capacitor, split-phase and shaded-pole motors.

• Drives with stepper motors

Geometry and operating principle. Simplified dynamic model. Power supply circuits and control techniques. Low-speed and high-speed instability issues. Limit performance as a function of supply frequency.

• Drives for wind energy generation

State of the art and Italian scenario of wind energy generation. Turbine types. Maximum Power Point Tracking, MPPT, algorithms. Role of electrical drives in wind energy conversion systems.

• Laboratory activities and application case studies

During the course, practical exercises will be carried out for the implementation and analysis of the main drives studied in the theoretical lectures. The activities will also include the analysis of real industrial case studies, the consultation of technical catalogues, and the application of criteria for component selection and sizing.

The practical activities are intended to connect theoretical models with the actual behaviour of electrical drives and to develop the ability to analyse systems, interpret technical data and choose suitable solutions according to the application.

Readings/Bibliography

The course covers and integrates topics related to electrical machines, electrical drives and their control systems. For this reason, the main study material for exam preparation consists of handouts, lecture notes and other teaching materials prepared by the instructor.

These materials will be made available on the University of Bologna Virtuale platform: virtuale.unibo.it.

The following books are recommended as reference texts for studying and further exploring the topics covered in the course:

• A.E. Fitzgerald, C. Kingsley Jr., A. Kusko, Macchine Elettriche, Franco Angeli Editore, Milan, 1978.
• J.M.D. Murphy, F.G. Turnbull, Power Electronic Control of AC Motors, Pergamon Press, Oxford, 1988.
• I. Boldea, S.A. Nasar, Electric Drives, CRC Press, New York.
• P. Vas, Vector Control of AC Machines, Oxford University Press, New York.
• T.J.E. Miller, Brushless Permanent-Magnet and Reluctance Motor Drives, Clarendon Press, Oxford, 1989.
• T.J.E. Miller, Switched Reluctance Motors and their Control, Clarendon Press, Oxford, 1993.
• T. Kenjo, Stepping Motors and their Microprocessor Controls, Clarendon Press, Oxford, 1985.
• W. Leonhard, Control of Electrical Drives, Springer-Verlag, Berlin, 2001.

For exam preparation, students should primarily refer to the teaching material provided by the instructor and made available on Virtuale. The books listed above are intended as supporting references and sources for further study on specific course topics.

Teaching methods

The course includes classroom lectures, integrated with computer-based exercises and laboratory activities using experimental setups provided by the instructor.

Classroom lectures are devoted to the theoretical foundations of electrical machines, electrical drives and their control systems. Computer-based exercises are aimed at consolidating the topics covered in class through the simulation of the behaviour of electrical machines and related control systems.

Laboratory activities allow students to observe and implement the electrical drives studied in the theoretical part of the course, helping them connect mathematical models, numerical simulations and the actual behaviour of physical systems.

The simulations developed by the instructor will be made available to students through the official teaching platform of the course.

Due to the type of activities and teaching methods adopted, participation in laboratory activities may require students to complete the appropriate safety training modules for study and laboratory environments, in accordance with the instructions provided by the Degree Programme and the University. Any specific information on safety training procedures and deadlines will be communicated through the course teaching platform.

 

Assessment methods

The assessment of learning is based on a written examination, aimed at evaluating the acquisition of the knowledge and skills covered by the course programme. In addition, students may choose to take an optional oral examination.

The final grade will be calculated as the average of the grade obtained in the written examination and the grade obtained in the optional oral examination, if taken.

• Structure of the written examination

The written examination is structured as follows:

1. True/False questions
The written examination includes 12 True/False questions, each consisting of 3 statements.

The score assigned to each statement is as follows:

• correct answer: +1/3 point;
• wrong answer: –1/6 point;
• no answer: 0 points.

The maximum score for this section is 12 points.

2. Open-ended questions
The written examination includes 3 open-ended questions, each graded up to 4 points.

The maximum score for this section is 12 points.

3. Short numerical exercises
The written examination includes 3 short numerical exercises, each graded up to 3 points.

The maximum score for this section is 9 points.

The maximum total score for the written examination is therefore 33 points.

• Optional oral examination

Students may access the optional oral examination only if the score obtained in the written examination is higher than 14/30.

The oral examination consists of open-ended questions to be discussed in person with the instructor.

The assessment of the oral examination will consider:

• correctness of the answers;
• clarity of presentation;
• appropriate use of technical language.

If the student takes the oral examination, the final grade will be calculated as the average of the grade obtained in the written examination and the grade obtained in the oral examination.

Assessment criteria for open-ended questions

The open-ended questions are aimed at assessing the student’s ability to:

• correctly use the tools of electrical engineering and electromechanical energy conversion;
• understand the operating principles of electrical machines;
• describe the principles and performance of electrical drives;
• represent control schemes.

• Laboratory activity as an alternative to the oral examination

As an alternative to the oral examination, students may carry out a laboratory-based project activity, either individually or in groups of up to 3 students.

The project will be assigned by the instructor, taking into account the composition of the group.

If successfully completed, the activity may award up to 3 additional points, to be added to the written examination score.

 

• 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/en ). 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.

• University Code of Ethics 

In accordance with the University Code of Ethics (Codice Etico di Ateneo), students’ attention is drawn to the obligation to adopt conduct based on the highest standards of integrity.
Any activity that may compromise the proper conduct of examinations is prohibited, including but not limited to:

• cheating and plagiarism;
• access to online learning resources;
• use of artificial intelligence tools not expressly authorized;
• use or possession of unauthorized materials or equipment.

It is specified that the mere possession of unauthorized tools or materials during the conduct of any examination results in the immediate invalidation of the submitted work and notification to the competent offices.

Any conduct in violation of the above provisions may result in disciplinary proceedings and, where criminal relevance applies, reports to the competent authorities, with the consequent risk of criminal proceedings being initiated against the students involved.

Teaching tools

Lectures are delivered with the support of a PC, video projector and PowerPoint presentations.

PDF files of the slides used during the lectures will be made available to students through the official teaching platform of the course. Additional teaching materials, handouts, simulations and exercises prepared by the instructor may also be provided through the same platform.

These materials are intended to support individual study, review of the topics covered in class and preparation for the final examination. Any additional software tools or digital resources required for the exercises will be indicated by the instructor during the course.

Office hours

See the website of Michele Mengoni