Browsing by Author "Lima, Marco"
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- 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, ElmanoThe main power supply of a Fast Field-Cycling Nuclear Magnetic Resonance (FFC-NMR) is the key element comparing the performance of different solutions. The power supply is a current source that supplies a magnet being the current controlled in order to perform adjustable and repetitive current cycles. This power supply can be based on different topologies, operating principles and controlled using distinct techniques. If for the final users of this experimental technique the current cycles of the equipment is the core feature, for the developers also the power losses distribution needs to be analyzed in order to develop efficient solutions. In this paper, the power losses and the dynamic behavior of two solutions for the FFC-NMR power supply are compared and discussed.
- Reversible current power supply for fast-field cycling nuclear magnetic resonance equipmentPublication . Lima, Marco; Sousa, Duarte M.; Roque, António; Margato, ElmanoThe Fast Field-Cycling Nuclear Magnetic Resonance (FFC-NMR) is a technique used to study the molecular dynamics of different types of materials. The main elements of this equipment are a magnet and its power supply. The magnet used as reference in this work is basically a ferromagnetic core with two sets of coils and an air-gap where the materials' sample is placed. The power supply should supply the magnet being the magnet current controlled in order to perform cycles. One of the technical issues of this type of solution is the compensation of the non-linearities associated to the magnetic characteristic of the magnet and to parasitic magnetic fields. To overcome this problem, this paper describes and discusses a solution for the FFC-NMR power supply based on a four quadrant DC/DC converter.