Courses

Electrical Machines and Motor Drive Systems I

General

Course Contents

1. Basic principles from rotating systems mechanics: angular speed, mechanical power of a rotating shaft, moment of inertia, Newton’s law for rotation, energy, mechanical work, power, principle of energy/power conservation. Introduction: basic families of motor drives converters and indicative applications, basic mathematical principles (DC and rms values of voltage and current waveforms).
2. Basic principles from electromagnetic fields theory (electrotechnology). Magnetic flux production. Permanent magnets, electromagnets, ferromagnetic materials, magnetization (hysteresis) curve. DC and AC electrical circuits, using switches: state-space analysis and equations, plotting of current waveforms, basic calculations and examples.
3. Faraday’s induction law, Laplace force on a current carrying conductor, electromotive (emf) force on a conductor that moves inside a magnetic field. Magnetic flux density and intensity.. Measurement units Wb, T, A/m. Basic power electronics switches in motor drives converters: diode, thyristor, power transistor, IGBT, MOSFET, GTO, characteristics and applications examples.
4. Transformers. Power diodes: use, selection, basic circuits with power diodes (single and three phase), ripple calculations, capacitor charging/discharging issues, examples. Diode converters specifications.
5. The simplest electrical machine: two conductors inside a constant magnetic field. Voltage production, torque production. Brushes. The general case for more conductors. Equations E=kωφ anf T=kIφ. Structure of a DC machine. Thyristors: use, selection, basic circuits with controlled AC/DC motor drive converters (single or three phase) using thyristors, ripple calculations, examples. Thyristor converters specifications.
6. Armature reaction, distortion of magnetic field, reduction of magnetic flux under load conditions, solutions applied. Winding types, lap and wave windings. Construction details: axis (shaft), bearings, fan, commutator, brush holders, cooling fins, technological materials. The principle of “power quality”: harmonics in power networks, origin, presence in dc and ac systems, effects, harmonic standards requirements, THD.
7. Type of DC motors excitations: permanent magnets (PM), separately-parallel-in series-compound excited machines. Speed/torque characteristic for each type of excitation. Typical applications of each type of the machines. Introduction to single phase inverters with power transistors: basic operational principles, principles of modulation, PWM, applications and examples.
8. Speed control in a DC motor. Variable speed drives (DC drives): principle of operation and industrial applications. PWM operating principles, basic control parameters, implementation of sinusoidal PWM and applications in DC/AC converters. PWM harmonics. Examples and design.
9. AC machines classification map. Terminology. The permanent magnet synchronous machine as a reversed DC machine. Rotating magnetic field. Brushless commutation in the stator. Similarities and differences with the DC machine. Three phase inverters with power transistors: basic operating principles, 6 pulse and PWM operation. Applications in motor drive systems. Introduction to basic motor control principles.
10. Introduction to the permanent magnet synchronous motor: PMAC, PMSM and BLDC machines. Drives requirements for operating synchronous motors. Starting torque and acceleration procedure. Description of a basic servo drive. Speed control. AC motor drives operating principles – control methods.
11. Short introduction to separately excited synchronous machines as generators. Special machines for servomotor systems: step motor, synchro machine etc. Short introduction to induction motors. Capability of producing a magnetic field from the rotor without PM or electromagnets. DC/DC step down (buck) converter: operating principle, design, application, voltage control.
12. The rotating transformer. Types of rotor winding in an induction motor: squirrel cage and wound rotor machines. Slip. The nameplate of an induction motor. Star (Y) and Delta (D) connection. Terminal box. DC/DC step up (boost) converter: operating principle, design, application, voltage control.
13. The equivalent circuit of an induction motor. Parameters that influence the magnetizing current. Speed control with VFD. Speed/torque characteristic for a squirrel cage and wound rotor machine. Wound rotor machine application in contrast to the squirrel case. Power losses in an induction motor. Examples, exercises. Operating principles of DC motor drives – control methods.

Educational Goals

The aim of the course is to provide theoretical and descriptive experience on the basic principles of electrical machines technology and the technology of the electronic power converters for motor driving. In particular, it puts emphasis on the documentation of the various types of electrical motors that have a significant role in industrial technological applications, the analysis of their operating principles, their construction details and their mathematical modelling. Furthermore, the course focuses also on electrical energy conversion applications with direct use in an industrial environment and motion applications such as AC/DC and DC/DC power supplies and DC/AC inverters, presenting their operational characteristics, their construction details and modelling principles. Being a course with a specific scientific and technological area focus, it offers to the new Industrial & Management Engineer the background for the comprehension and the implementation of various applications that refer to motor drive systems and their speed and torque control. In addition, it provides the opportunity to understand the use of power electronics converter systems for motor drives. The consistent and successful completion of the course, has the expected outcome to enable the student to:
a) identify the type of an electrical machine, classify it and be in a position to electrically connect it.
b) comprehend the basic properties of each type of an electrical machine and determine its mechanical and electrical behaviour.
c) select, based on technoeconomic criteria, the optimal type of electric motion for a particular application.
d) calculate the efficiency of a motor drive system.
e) take decisions on preventive and repressive maintenance of electrical motors.
f) be in a position to classify the various power electronic converters based on their characteristics and the type of application.
g) be in position to understand the basic operational specifications of an existing (currently in use) power electronic converter and to set the necessary specifications of new converters based on the intended application.
h) comprehend the operational characteristics of a converters, the potential impact of their operation on power quality in an industrial environment and the ways to alleviate the consequences.
i) understand the construction characteristics and the structure of the converters, so that, if possible, to be in a position to replace parts or perform maintenance.
j) understand the basic principles of power converters use for industrial control of energy supply and motion systems.
k) be in a position to perform basic design of power converters use, depending on the application.

General Skills

Practical application of knowledge, search, analysis and synthesis of information and data using appropriate technologies; Adjustment to new situations; Decision making; Autonomous work; Team work; Work in an interdisciplinary environment.
Design and project management; promotion of free, creative and inductive thinking; priorities setting; production of new research ideas; compliance to guidelines of good practices.

Teaching Methods

Class theory, teaching in discussion groups and students’ active participation. The lectures are supported by presentations of the total content, while the whiteboard is used: a) for further elaboration of selected thematic sections, b) for the promotion of the students’ active participation in step-by-step problems solving and examples process.

Students Evaluation

The course grade is formulated by a final written exam which may contain: multiple choice questions, problems solving based on knowledge acquired, short answers’ questions, comparative assessment of theoretical principles.

Recommended Bibliography

1. Chapman S., «Electric Machinery Fundamentals», 5th Edition, ISBN-13: 978-0073529547, McGraw Hill
2. Fitzgerald, Kinglsey, Umans, “Electric Machinery”, 6th Edition, ISBN-13: 978-0071230100, McGraw Hill
3. Mohan N., Undeland T and Robbins W, “Power Electronics: Converters, Applications and Design”, ISBN-13: 978-0471226932, John Wiley & Sons Inc.