28633 - Electrotechnics T-A (A-K)

Learning outcomes

At the end of the course, the student will have knowledge of the fundamental properties of electrical circuits, the main methodologies of circuit analysis, the basic principles on which the transmission and distribution of electrical energy are based, magnetic circuits, the basic laws of electrical machines and the operating principles of the transformer.

Course contents

Definition of fundamental quantities and laws

Definition of circuit theory and electrical circuit, the definition of voltage, current, power, and energy. Kirchhoff's laws. Basic circuit elements: resistor and idea sources. Ohm's law.

Direct current circuits

Analysis of resistive circuits with one generator. Series and parallel connection, voltage divider, and current divider. Solution of circuits by simplification. Circuit properties and methods of analysis: superposition of effects, Millman's theorem, Thevenin's and Norton's theorems, nodal analysis, mesh analysis. The principle of maximum power transfer

Transients

Introduction to transient circuits, the definition of basic circuit elements: capacitor, inductor. First-order circuits. Study of first-order transients RL and RC using equations of state

Sinusoidal steady-state

Definition of sinusoidal steady-state, periodic quantities, sinusoidal quantities, operations between isofrequential sinusoidal quantities. Symbolic method: phasors. Operations with phasors: a reminder of the algebra of complex numbers; properties of phasors. Kirchhoff's laws in symbolic form, constitutive laws of electrical components in symbolic form: impedance and generalized Ohm's law. The generalization of principles and theorems in the phasor domain, phasor diagram.

Power in sinusoidal steady-state circuits: instantaneous power, active and reactive power, complex and apparent power. Maximum power transfer in sinusoidal steady-state. Boucherot's theorem. Power factor correction of single-phase loads.

Three-phase circuits

Origins of three-phase systems. Definitions: symmetrical system, balanced system, phase voltages, line-to-line voltages, three-wire system, four-wire system. Star connection and delta connection; three-phase loads in series and parallel. Equivalent single-phase circuit. Three-phase power factor correction: star and delta connection of power factor correction capacitors. Connection of single-phase loads.

Recalls of magnetostatics and magnetic circuits

Diamagnetic, paramagnetic and ferromagnetic materials. Magnetic circuits with lumped parameters; Hopkinson's law. Self and mutual induction coefficients. Lorentz force. Definition of hard and soft ferromagnetic materials. Hysteresis. Application: differential switch.


The transformer

Principle of operation of single-phase transformer; ideal transformer; hysteresis and eddy current losses; transformer equivalent circuit. Three-phase transformer.

Elements of electrical power systems

Notes on electrical power generation systems. Scheme of an electrical system. Comparison of direct current and single and three-phase alternating current transmission lines. Protection against electrical faults and accidents: overvoltage and overcurrent; fuse, magnetic, thermal, and differential relay; earth system and coordination with differential relays.

Readings/Bibliography

Suggested books:

• “Elettrotecnica: elementi di teoria ed esercizi”, M. Repetto e S. Leva, Città studi edizioni.
  
  
• “Electric circuits”, Charles K. Alexander, Matthew N. O. Sadiku, McGraw-Hill Education.
  
  
• "Circuiti elettrici" di R. Perfetti, Zanichelli.

Teaching methods

The course consists of lectures and exercises. Handouts and compendium material will be provided by the lecturer and uploaded on the course webpage.

Assessment methods

The assessment of learning takes place through a final examination that ascertains the acquisition of the expected knowledge and skills by means of a written test lasting approximately 1.5 hours.

The written test consists of a first part consisting of a series of multiple-choice questions and numerical exercises (for a maximum score of 20/30) and a second part consisting of two open-ended questions (for a maximum score of 10/30). The questions and exercises cover all the topics in the syllabus.

Passing the examination is conditional on achieving a minimum mark of 12/30 in the first part.

A pass mark will be guaranteed for students who demonstrate mastery and operational ability in relation to the key concepts illustrated in the teaching, and in particular in relation to the fundamental concepts of circuit theory and the ability to solve electrical and magnetic circuits. A higher mark will be awarded to students who are able to use and link together all the teaching content. Failure to pass the examination may be due to insufficient knowledge of the key concepts.

Office hours

See the website of Mattia Simonazzi