Transformers and Asynchronous Machines

Recommended Prerequisites

Electrical Energy Conversion.

Teaching Methods

Theoretical lectures in the black board and with the aid of Powerpoint slides for the presentation of the concepts, principles and fundamental theories about the topics covered in the curricular unit. Theoretical-practical classes to solve problems and exercises that illustrate the application of the theoretical concepts to real cases in the engineering world. In these classes, some simulations in Matlab/Simulink environment are performed to simulate the behaviour of the systems under study. Laboratory classes to validate the theoretical and practical concepts addressed in the curricular unit.

Learning Outcomes

It is intended that students acquire skills in the following topics: (i) three-phase power transformers, especially under asymmetric regimes, voltage and current transformers, special transformers; predictive maintenance; (ii) asynchronous machines (classic theory): design and main constructional aspects; steady-state operation and performance; predictive maintenance.

Work Placement(s)

No

Syllabus

Three-phase transformers: equivalent circuit and no-load and short-circuit tests; magnetic saturation and excitation current; vector group; parallel operation of transformers; asymmetrical operation of three-phase transformers; tertiary windings; bank of single-phase transformers. Special transformers: autotransformers; instrumentation transformers (voltage and current transformers). Cooling system, monitoring and protection of transformers. Predictive maintenance of power transformers.

Asynchronous machines: design of armature windings; distribution of the magnetomotive force and induced voltages; types of rotor; equivalent circuit; no-load and blocked-rotor tests; operation in steady-state; effects of rotor resistance variation; operation modes. Selection and applications. Service classes and service factor. Insulation classes. Predictive maintenance of three-phase induction motors.

Head Lecturer(s)

Sérgio Manuel Ângelo da Cruz

Assessment Methods

Assessment 1
Other: 20.0%
Project: 25.0%
Frequency: 55.0%

Assessment 2
Other: 20.0%
Project: 25.0%
Exam: 55.0%

Bibliography

D. Kothari, I. Nagrath: “Electric Machines”, Tata McGraw-Hill, New Delhi, 2010.

S. Chapman: “Electric Machinery Fundamentals”, 5th edition, McGraw-Hill, New York, 2012.

Fitzgerald, C. Kingsley, S. Umans: “Electric Machinery”, 6th edition, McGraw-Hill, New York, 2003.

Boldea, L. Tutelea: “Electric Machines – Steady state, transients and design with Matlab”, CRC Press, Boca Raton, 2010.

IEC 60044-1: “Instrument transformers – Part 1: Current transformers”, Ed. 1.2, 2003.