Lecturer: Ezio Bassi  

Course name: Electrical Drives
Course code: 503131
Degree course: Ingegneria Elettrica
Disciplinary field of science: ING-IND/32
L'insegnamento è caratterizzante per: Ingegneria Elettrica
University credits: CFU 9
Course website: n.d.

Specific course objectives

The course outlines in its first half the basic concepts about functional characteristics, design and applications of electrical variable speed drives at steady state, with a few hints on their control and transient behavior. In the second part are addressed items concerning the dynamical behavior of electrical drives: various regulation schemes are introduced, principally with induction and brushless motors, with different solutions as to the controlled variables and the regulation algorithms.

Course programme

Electrical Drives are made up of electric machines fed by static power converters which are properly regulated to drive a load according to the requirements of a given application. They are employed in a variety of industrial processes and for a broad range of power at fixed- or variable-speed, such as with fans, pumps, compressors, in the manufacturing industry, in robotics and automation and for the electric traction. The course describes firstly the basic principles of electrical drives and their stead-stare operation; in the second part are presented items relating to the dynamic behavior of drives and to aspects of control and regulation

General issues on drives
Characteristics of loads and operating requirements to be satisfied by the drive; principle of electromechanic conversion; reversible operation of electrical machines; thermal, electrical and magnetic limits of electric systems; Block diagram of an electrical drive; review of applications

Electrical machines
Electrical machines for production and transformation of electrical energy; operating aspects (steady-state), range of power and efficiency, rated values. D.c. machine: tranfer function, operation fed by SCR rectifier, simple control schemes; induction motor: operation fed from variable-frequency inverter at constant flux; influence of frequency and harmonic equivalent circuit

Power Converters
Static power converters: principle of operation and external characteristics; fields of application; rectifier feeding a d.c. machine: analytical description, continuous and discontinuous operation; 3-phase voltage-sourceinverter: basic operation and PWM control of voltage and frequency (triangular carrier PWM)

Induction motor:
dynamic model and instantaneous torque, d-q (Park) transfomations and equations in vectorial form; direct and indirect Field Oriented Control; Direct Torque Control; reconstruction of rotor and stator flux; field weakening operation; Current-Source Inverter Drive with regeneration.

A.C. current control
Control of the currents of a three-phase system (i.e. motor) in different reference systems (abc, αβ, dq); PI regulators; Hysteresis regulators; predictive control; compensation of dq coupling terms.

Space Vector PWM
Inverter configurations, voltage reference and basic principles of the method, definition of the exagon and overmodulation, optimal sequence of inverter states, limitation of switching frequency and current ripple

Permanent Magnet Synchronous Motor
Permanent Magnets, construction and types of rotor, e.m.f. induced in the stator windings; magnet and reluctance torque; d-q dynamic model; closed-loop torque and speed control; field weakening operation.

Course entry requirements

Principles of electrical engineering and mechanics, periodic waveforms, vector diagrams, basic power electronics

Course structure and teaching

Lectures (hours/year in lecture theatre): 50
Practical class (hours/year in lecture theatre): 40
Practicals / Workshops (hours/year in lecture theatre): 0

Suggested reading materials

Legnani, Tiboni, Adamini. Meccanica degli azionamenti, vol.1 - Azionamenti Elettrici . Progetto Leonardo, Bologna 2002.

W. Leonhard. Control of Electrical Drives . Springer Verlag, 1996.

B. K. Bose. Power Electronics and Variable Frequency Drives. Technology and Applications. IEEE Press, 1997.

L. Bonometti. Convertitori di potenza e servomotori brushless. UTET, 2001.

Mohan, Undeland, Robbins. Elettronica di potenza. Convertitori e applicazioni . Hoepli, 2005 .

Murphy, Turnbull. . Power Electronic Control of AC Motors. Pergamon Press, 1988.

E. Bassi. Lecture notes . Available only for some topic of the course.

Various Authors. Web Links to lecture notes available for a number of topics.

Testing and exams

Oral exam; before the exam the students are also required to undergo a written test on the very basic issues of the course. A written relation on specific subjects and the interest displayed during the lectures can also contribute to the evaluation