


Politecnico di Torino  
Academic Year 2017/18  
11BNMLX Electrical machines 

1st degree and Bachelorlevel of the Bologna process in Electrical Engineering  Torino 





Subject fundamentals
This course will present the main features of the most commonly used machines (based on 'iron and copper') in electrical energy conversion: transformers, D.C. machines, rotating field A.C. machines. All these devices will be analysed through the synthesis of equivalent electric circuits. Their main characteristics, both as generator and motor, will be deduced and discussed. Further considerations on their typical applications will be provided as well.

Expected learning outcomes
The objective of the course is to provide a basic knowledge the electromechanical conversion and the main methods used in the study of electrical machinery. Students should be able, also through mathematical instruments, to evaluate problems related to the use of electric transformers, motors and generators and to correctly estimate the supply and load limit conditions.

Prerequisites / Assumed knowledge
The recommended curriculum includes at least the knowledge of Mechanics, Circuit theory and Electromagnetism.

Contents
Transformer (28h)
' Basic operating principles. Construction aspects. ' Simplified theory of singlephase transformers. Equivalent circuit. Name plate values. ' Vector diagrams. Voltage drop . Kapp circular diagram. ' Inductive parameters and leakage reactance calculation. ' Transformers with multiple secondary windings. ' Simplified theory of threephase transformers; winding connections; groups of threephase transformers. ' Equivalent circuit for balanced load. Equivalent circuit with unbalanced loads. Homopolar impedance. ' Losses and efficiency. ' Sizing power of a transformer. Scale considerations. Autotransformer connection. ' Parallel operations. ' Tests and measurements. ' Particular operating conditions: Inrush currents. Short circuit stresses. Overvoltage surges. D.C. machine (12h) ' Basic operating principles. Construction aspects. ' Separately excited machine. Series excited machine. Permanent magnet motors. ' Electromechanical features and regulations. Operative quadrants. ' Dynamic behaviour of DC motor. ' Armature reaction. Nonlinear magnetic phenomena and their impact on the D.C. machine behaviour. ' Losses and efficiency. ' Commutation. ' DC motor applications and name plate values. Rotating Fields. (8h) ' A.C. windings. Airgap m.m.f. distributions. Harmonic contents. ' Magnetic field and Carter factor. ' Vector representation of rotating fields. ' Linked fluxes and induced e.m.f.. Asynchronous Machine (20h) ' Basic operating principles and constructive aspects. ' Asynchronous machine equivalent circuit. Vector diagram. ' Energy balance discussion. The concept of transmitted power. Single and double fed machines. ' Main electromechanical features; torque and current characteristics; influence of parametric variations. ' Field harmonics and their effects: synchronous and asynchronous torques. ' Circular diagram. ' Typical operations; starting and braking; stator frequency regulation. Rotor regulations (DoubleFedInductionMotor/DoubleFedInductionGenerator). ' Tests and measurements. Efficiency evaluations. Name plate values. ' Fractional horsepower motors. Singlephase motors. Singlephase shadedpole motors. Synchronous machine (16h) ' Basic operating principles and constructive aspects. ' Isotropic and anisotropic machine; dq axes theory. ' BehnEschenburg and Potier equivalent circuits. Electrical equations. Synchronous reactance. ' Vector diagrams. Effects of magnetic nonlinearities. ' Energy balance and torque. ' Mainconnected generator. Active and reactive power regulation. Static and dynamic stability. Circular diagram and name plate values. ' Selfstanding generator. Application examples. ' Permanent magnet and reluctance motors. Drive methods. ' Measurements and testing. 
Delivery modes
Tutorials are held in the computer laboratory of the Electric Engineering Department. They consist in performance computations and measurement developments of the electrical machines presented in the course (20 h).
4 visits to the Electrical Machines Laboratory of the Electric Engineering Department are also provided, in order achieve a direct experience of the main phenomenon presented in the theoretical lessons (8h). 
Texts, readings, handouts and other learning resources
The educational material relating to lectures and tutorials will be available on the personal students portal. Books and scientific documentation for study of specific subjects will be suggested by the teacher.

Assessment and grading criteria
The examination consists of an oral test that includes four questions, one for each of 4 machines studied. The student must correctly answer all four questions to pass the exam.

