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- Thermal Analysis of Synchronous Reluctance MachinesPublication . Adouni, Amel; Cardoso, A. J. M.Synchronous Reluctance Machines (SynRMs) are facing a revamped industrial interest. A comparison between SynRMs and other types of electric machines allow listing the advantages and proving the choice of such machines. This paper presents a review of SynRMs, regarding particularly their thermal analysis. First of all, a description of the basic principles of SynRM is illustrated. The thermal analysis is based mainly on the study of the heat sources and the heat extraction mechanisms which are listed and described. Nevertheless, the coupling effects between the thermal field and the magnetic material parameters are discussed. Then, the three heat extraction phenomena (conduction, convection and radiation) are analyzed. Along the work, important facts about the thermal analysis are discussed. A comparison between the different approaches used for the thermal analysis is highlighted, and new developments and perspectives are identified.
- Open-Circuit Fault Diagnosis and Fault Tolerant Operation of Interleaved DC–DC Boost Converters for Homes and OfficesPublication . Bento, Fernando; Cardoso, A. J. M.The use of electronic equipment and other dc-compatible appliances in homes and offices is increasing at a very fast rate, as well as the distributed generation of energy. These two statements will most likely trigger, in a near future, the adoption of district-scale dc grids, connecting dc microgeneration plants and consumers, in an effort to cut the number of conversion steps required to deliver power to dc appliances. DC-DC converters will be fundamental in these systems, allowing the establishment of several voltage levels. The reliability of these converters plays a critical role, ensuring service continuity of the loads connected to them. With the increment of reliability in mind, this paper proposes a simple yet effective open-circuit fault diagnostic method suitable for interleaved dc-dc boost converters, but equally functional for other dc-dc converter topologies. The improvements introduced in this paper greatly simplify the diagnostic action, while making the correct diagnostic of faults independent of the switching duty cycle. Moreover, an alternative reconfiguration scheme is proposed to mitigate the adverse impacts of such faults. To prove the effectiveness of these strategies, a three-phase interleaved boost converter prototype was used in the experiments.
- Fault-Tolerant Back-to-Back Converter for Direct-Drive PMSG Wind Turbines Using Direct Torque and Power Control TechniquesPublication . Jlassi, Imed; Cardoso, A. J. M.Fault tolerance in wind turbines is considered crucial to increase their reliability and availability levels. This paper presents a fault-tolerant direct-drive permanent magnet synchronous generator (PMSG) using new direct control techniques, with the ability to handle power semiconductor open-circuit faults in the full-scale back-to-back converter. The fault-tolerant topology consists of a five-leg converter, with a shared leg connected to a generator phase and to its corresponding grid phase, through a triode for alternating current (TRIAC). The main contribution of this paper consists of the development of an alternative direct torque control and direct power control schemes for both machine-side converter and grid-side converter, respectively. Moreover, a reliable fault diagnostics algorithm without requiring additional sensors is also integrated, providing the information required to instantaneously trigger fault-tolerant remedial strategies. Simulation and experimental results are presented to validate the effectiveness of the proposed fault-tolerant PMSG drive.
- Diagnosis of Open-Switch and Current Sensor Faults in PMSM Drives Through Stator Current AnalysisPublication . Khojet El Khil, Sejir; Jlassi, Imed; Cardoso, A. J. M.; Estima, Jorge; Mrabet-Bellaaj, NajibaFault detection and fault accommodation, as well as fault tolerance, are important issues in closed-loop controlled three-phase converters. For such systems, power semiconductors and sensors are the most affected components by the occurrence of failures. Therefore, fault diagnosis and remedial operating strategies involving such components are highly required. In this paper, a new reliable approach is proposed, which aims to diagnose current sensor faults and power semiconductor open-circuit faults in permanent magnet synchronous motor drives. The proposed fault diagnosis scheme uses only the measured currents, which makes it suitable for real-time implementation. The performance of the proposed technique is analyzed through experiments.
- Using finite element method based software to teach electrical machines-The linear switched reluctance actuatorPublication . Calado, M. Do Rosário; Espírito Santo, António; Salvado, José A.; Cabrita, Carlos; Mariano, S.In this paper, the authors intend to propose a method to teach Electrical Machines in Electrical Engineering courses. The way that both in textbooks and classrooms treat this subject seems to limit students' understanding. The competences on electrical machines design and analysis are improved by a practical approach based on simulation and numerical analysis using Finite Element Method Software. As a complement to the previous teaching method, the students use an experimental test bench to verify the numerical results. A particular topic, concerning the study of the Linear Switched Reluctance Actuators, is here presented. Therefore, we propose a guideline for use in the classroom.