Browsing by Author "Sousa, Duarte M."
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- Charging electric vehicles from photovoltaic generation with intermediate energy storagePublication . Silva, Carlos; Sousa, Duarte M.; Roque, António
- Comparing the Power Losses of Power Supplies for Fast-Field Cycling Nuclear Magnetic Resonance EquipmentPublication . Lima, Marco; Pereira, Bruno; Sousa, Duarte M.; Roque, António; Margato, ElmanoThe main feature of the Fast-Field Cycling (FFC) Nuclear Magnetic Resonance (NMR) power supplies is to drive a controlled current fulfilling the requirements of this technique. This feature allows fast switching the current of the FFC magnet and performing accurate and repetitive current cycles. When designing this equipment the power losses is not a fundamental parameter of the optimization process but are estimated in order to validate the topology of the final solution giving that the efficiency of the power solution influences the power consumption, and therefore the operational costs, which should be minimized. Under this context, from the power efficiency viewpoint, the power losses of two possible solutions are compared and discussed in this paper. Typical FFC current cycles are used as reference in order to balance the pros and cons of both solutions.
- Comparing two Power Supplies for Fast-Field Cycling Nuclear Magnetic Resonance Relaxometers: Power Losses and PerformancePublication . Lima, Marco; Pereira, Bruno; Sousa, Duarte M.; Roque, António; Margato, Elmano
- Control of a Power Supply with Cycling Current Using Different ControllersPublication . Roque, António; Maia, José; Margato, Elmano; Sousa, Duarte M.; Marques, GilFast Field Cycling (FFC) Nuclear Magnetic Resonance (NMR) relaxometers require controlled current sources in order to get accurate flux density with respect to its magnet. The main elements of the proposed solution are a power semiconductor, a DC voltage source and the magnet. The power semiconductor is commanded in order to get a linear control of the flux density. To implement the flux density control, a Hall Effect sensor is used. Furthermore, the dynamic behavior of the current source is analyzed and compared when using a PI controller and a PD2I controller.
- Development of a System for the Usability of Forest Residuesfor Electric Energy ProductionPublication . Baranovschi, S.; Roque, António; Sousa, Duarte M.; Fernão Pires, Vítor
- Digital Control of a FFC NMR relaxometerPublication . Lopes, R.; Sebastião, Pedro; Sousa, Duarte M.; Roque, António; Cascais, J. M.
- Electromagnetic and Thermal Aspects of a FFC-NMR Equipment Magnet and Power SupplyPublication . Pereira, Bruno; Sousa, Duarte M.; Roque, António
- FFC NMR relaxometer with improved magnetic field uniformityPublication . Roque, António; Sousa, Duarte M.; Sebastião, Pedro Silva; Cascais, J. M.
- FFC NMR Relaxometers on Education Topologies, control techniques and electromagnetic devicesPublication . Roque, António; Sousa, Duarte M.; Margato, Elmano; Marques, Gil; Sebastião, Pedro José
- Magnetic Flux Density Distribution in the Air Gapof a Ferromagnetic Core With SuperconductingBlocks: Three-Dimensional Analysis andExperimental NMR ResultsPublication . Roque, António; Sousa, Duarte M.; Margato, Elmano; Machado, Vítor; Sebastião, Pedro; Marques, G.D.The design of magnetic cores can be carried out bytaking into account the optimization of different parameters inaccordance with the application requirements. Considering thespecifications of the fast field cycling nuclear magnetic resonance(FFC-NMR) technique, the magnetic flux density distribution,at the sample insertion volume, is one of the core parametersthat needs to be evaluated. Recently, it has been shown that theFFC-NMR magnets can be built on the basis of solenoid coilswith ferromagnetic cores. Since this type of apparatus requiresmagnets with high magnetic flux density uniformity, a new typeof magnet using a ferromagnetic core, copper coils, and supercon-ducting blocks was designed with improved magnetic flux densitydistribution. In this paper, the designing aspects of the magnetare described and discussed with emphasis on the improvement ofthe magnetic flux density homogeneity(ΔB/B0)in the air gap.The magnetic flux density distribution is analyzed based on 3-Dsimulations and NMR experimental results.