Electric Circuits, Applied Electrotechnics
Theoretical classes with detailed presentation, using audiovisual means, of the concepts, principles and fundamental theories about the topics covered in the curricular unit. Besides the theoretical aspects, these classes include the resolution of problems and exercises that illustrate the practical interest of the topics covered and exemplify its application to real cases in the engineering world. Laboratory classes allow the student to validate the majority of the theoretical concepts addressed in the unit.
Is intended that students acquire skills in the following topics: (i) Three-phase power transformers, especially under asymmetric regimes, measure and protection transformers, special transformers; (ii) asynchronous machines (classic theory): principle of operation; steady-state operation and performance; selection and their application.
Part I - Three-phase transformers: equivalent circuit and no-load and short-circuit tests; magnetic saturation and excitation current; phase shift between primary and secondary quantities; parallel operation of transformers; asymmetrical operation of three-phase transformers; abnormal regimes in transformers; tertiary windings; bank of single-phase transformers. Special transformers: autotransformers; instrumentation transformers (voltage and current transformers).
Part II - Asynchronous machines (Classical theory): types of windings; distribution of the magnetomotive force and induced voltages; rotating field; rotor configuration; equivalent circuit; no-load and blocked-rotor tests; induction machine steady-state – electromagnetic torque, mechanical power, efficiency and power factor correction, circle diagram; effects of rotor resistance on the performance of the machine; operating modes. Selection and applications. Service classes and service factor. Isolation class.
Sérgio Manuel Ângelo da Cruz
Assessment A
Laboratory test : 25.0%
Two midterm tests: 75.0%
Assessment B
Laboratory test : 25.0%
Exam: 75.0%
S. Chapman (2012), Electric Machinery Fundamentals, 5th edition, McGraw-Hill, New York.
A. Fitzgerald, C. Kingsley, S. Umans (2003), Electric Machinery, 6th edition, McGraw-Hill, New York.
Enrique Ras (1977), Transformadores de potência de medida e de protecção, Livraria Almedina, Coimbra.