High power factor rectifiers have been consolidated as an effective solution to improve power quality indices in terms of input power factor correction, reduction in the total harmonic distortion of the input current and also regulated dc voltages. Within this context, this subject has motivated the introduction of numerous converter topologies based on classic dc-dc structures associated with novel control techniques, thus leading to the manufacturing of dedicated integrated circuits that allow high input power factor by adding a front-end stage to switch-mode converters. In particular, boost converters in continuous current mode (CCM) are widely employed since they allow obtaining minimised electromagnetic interference levels. This work is concerned with a literature review involving relevant ac-dc single-phase boost-based topologies with high input power factor. The evolution of aspects regarding the conventional boost converter is shown in terms of improved characteristics inherent to other ac-dc boost converters. Additionally, the work intends to be a fast and concise reference to single-phase ac-dc boost converters operating in CCM for engineers, researchers and experts in the field of power electronics by properly analysing and comparing the aforementioned rectifiers.

This work presents a comparative study of singlephase boost-based ac-dc converters applied to power factor correction. Three structures are chosen for this purpose and analyzed in detail e.g. the classical boost converter, the bridgeless boost converter, and the boost converter based on the three-state switching cell (3SSC) operating in continuous conduction mode (CCM). The aforementioned topologies are briefly revised so that they can be properly designed and validated considering results obtained from simulation tests, where aspects such as the input current, regulated output voltage, harmonic content, and dynamic response are investigated.I.

ResumoUm ensaio por partículas magnéticas é um método não destrutivo utilizado na detecção de descontinuidades superficiais e subsuperficiais em produtos laminados. Este método consiste em submeter a peça a um campo magnético, com aglomeração de partículas magnetizáveis nos pontos onde há descontinuidade. As partículas usadas podem ser de diferentes cores, dimensões e formas. A partícula fluorescente sob a luz ultravioleta demonstra melhor resultado para detecção de pequenas descontinuidades. Para ampliar o campo de visão ensaiado e realçar o contraste entre partícula e peça a radiação ultravioleta deve garantir uniformidade, intensidade e comprimento de onda adequado. Essas exigências motivaram o trabalho da Gerdau junto com a Metal Chek, representante da Spectroline, no desenvolvimento de uma solução inovadora. Na Linha de Inspeção de Tarugos da Gerdau Ouro Branco o uso de luminárias ultravioletas de LED -Light Emitting Diode tornou-se uma alternativa que proporcionou ganho em eficiência e em confiabilidade na tomada de decisão do inspetor de qualidade, baixo consumo de energia, custo de manutenção e satisfação dos clientes. A implantação das luminárias de LED refletiu na prática a evolução da qualidade do produto, além de melhores condições em meio ambiente, saúde e segurança para o inspetor. Palavras-chave: Partícula magnética fluorescente; Luz ultravioleta; LED -Light Emitting Diode; Qualidade. USING UV LED IN MAGNETIC PARTICLE TESTING IN THE LINE OF BILLETS INSPECTION OF GERDAU OURO BRANCO AbstractA magnetic particle testing is a non-destructive method for detecting discontinuities in surfaces and subsurfaces in laminated products. This method consists of submiting the product to a magnetic field, with an agglomeration of magnetizable particles at the points where there is discontinuity. The particles used may have different colors, sizes and shapes. The fluorescent particle under ultraviolet light shows a better result for the detection of small discontinuities. To expand the field of view tested and in order to highlight the contrast between particle and item, the ultraviolet radiation must ensure uniformity, intensity and appropriate wavelength. These requirements motivated the work of Gerdau along with Metal Chek, representant of Spectroline, in the development of an innovative solution. In the Line of Billet Inspection of Gerdau Ouro Branco, the usage of ultraviolet lamps of LED -Light Emitting Diode, became an alternative that provided efficiency and reliability gains in the decision making process of the quality inspector, low power consumption, cost maintenance and customer satisfaction. The introduction of LED lamps reflected in the evolution of product quality, better environmental conditions, health and safety to the inspector.