5,275 research outputs found
LC compensators for power factor correction of nonlinear loads
No full textThis material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of Brunel University's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. Copyright @ 2004 IEEEA method is presented for finding the optimum fixed LC compensator for power factor correction of nonlinear loads where both source voltage and load current harmonics are present. The LC combination is selected because pure capacitive capacitors alone would not sufficiently correct the power factor. Optimization minimizes the transmission loss, maximizes the power factor, and maximizes the efficiency. The performance of the obtained compensator is discussed by means of numerical examples
LC compensators based on transmission loss minimization for nonlinear loads
No full textThis material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of Brunel University's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. Copyright @ 2004 IEEEThis paper presents a method employing the penalty function search algorithm to determine the LC compensator value for the optimal power factor correction in nonsinusoidal systems. The objective of the proposed method is to minimize the transmission loss while the power factor and efficiency are taken as constraints and utilized in order to solve the multiobjective optimization problem by transforming it into a single objective one. Examples show that the load nonlinearity can have a significant impact on optimal compensator sizes
Qualidade de vida relacionada a saude de trabalhadores: um estudo de caso
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro TecnologicoO termo qualidade de vida implica na inter-relação mais ou menos harmoniosa dos vários fatores que moldam e diferenciam o cotidiano do ser humano e resulta numa rede de fenômenos, pessoas e situações. Muitos fatores de natureza biológica, psicológica e sócio cultural, tais como: saúde fisica, saúde mental, longevidade, satisfação no trabalho, relações familiares, disposição, produtividade, dignidade e até mesmo espiritualidade estão associados ao termo qualidade de vida. A sociedade moderna tem tornado a vida cada vez mais estressante. Neste contexto a qualidade de vida e a saúde do trabalhador tornam-se comprometidas, por isso é necessário alcançar um nível de excelência em relação à produtividade e a qualidade do trabalho prestado. O objetivo principal deste estudo foi traçar um perfil da qualidade de vida relacionada à saúde dos trabalhadores de uma empresa segundo sexo e idade. Para tanto, foi aplicado um questionário visando levantar os hábitos de saúde, queixas principais, histórico de doenças cardiorrespiratórias, prontidão para a prática de exercício físico, bem como a realização de medidas antropométricas, para estimar o grau nutricional dos trabalhadores, também foi analisado o perfil lipídio dos sujeitos (colesterol total, colesterol de alta densidade e triglicerídeos). Através da análise dos resultados pode-se verificar que um grande número de mulheres (45%) são fumantes, estas também apresentaram maiores níveis de estresse e cansaço. Também foi observado que os homens em todas as faixas etárias apresentaram níveis de gordura corporal elevados, bem como, um aumento de níveis lipídicos entre os grupos mais velhos. Desta forma, pode-se traçar um perfil do atual estado de saúde dos trabalhadores, bem como sugerir recomendações necessárias para melhorar a saúde dos trabalhadores da empresa analisada
Cost-effective applications of power factor correction for nonlinear loads
No full textThis material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of Brunel University's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. Copyright @ 2005 IEEEThe objective of this paper is to propose a new approach for designing passive LC compensators by using the penalty function method as an optimization tool. The performance of the cost-effective passive LC compensator for a constant load depends on the appropriate inductor and capacitor selection. Several design methods are reviewed and a novel design methodology is proposed in this paper. By using the proposed method, the designer can quickly find appropriate parameter values to meet the desired circuit performance. Simulated results show that an appropriate combination of the inductor and capacitor selected by the proposed method can meet the desired power-quality requirement. Different cases of design examples are shown in this paper to verify the performance of the proposed design methodology
NA PARÁBOLA DO HOMO VIATOR (LC 10, 25-37): A QUALIDADE DE VIDA ESCATOLÓGICA
No full textUn diseño ético de la parábola del buen samaritano (Lc 10: 25-37) proporcionará una narrativa sobre otra calidad de vida. La parábola apunta a las diversas formas de la calidad de vida, que van desde la calidad telúrica de la vida, pasando por la calidad de vida poética, hasta llegar a la calidad de vida escatológica como la verdadera calidad de vida. El relato bíblico del Desvalido en el camino refiere una nueva forma de referenciar esa otra calidad de vida, como una calidad soteriológica de la vida humana en este mundo. El Desvalido vive la calidad de vida soteriológica porque la vive como hospitalidad poiética y como ética soteriológica. La otra calidad de vida da un sentido ético a la calidad de vida poética.Um desígnio ético da parábola do Bom Samaritano (Lc 10, 25-37) será apresentar uma narrativa sobre a Outra qualidade de Vida. A parábola aponta para variadas for-mas de qualidade de vida, que vão desde as qualidades telúricas de vida, passando pela qualidade de vida poiética, até atingir a qualidade de vida escatológica, como a verdadeira qualidade de Vida. A narrativa bíblica do Desvalido no Caminho refere uma forma nova de referenciar a outra qualidade de vida, como uma qualidade sote-riológica da vida humana neste mundo. O Desvalido vive na qualidade de vida sote-riológica, porque vive como hospitalidade poiética e como ética soteriológica. A outra qualidade de vida dá um sentido ético à qualidade de vida poiética
Relação entre estado nutricional e qualidade de vida em pacientes hemodialisados
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde. Programa de Pós-Graduação em Nutrição.A sobrevida dos pacientes em hemodiálise vem aumentando progressivamente, porém, a permanência por tempo indeterminado em tratamento dialítico compromete o estado nutricional e influencia negativamente a qualidade de vida desses pacientes. O objetivo deste estudo foi correlacionar o estado nutricional e a qualidade de vida de pacientes em hemodiálise. Foram avaliados 96 indivíduos da Associação Renal Vida de Santa Catarina. Os indicadores laboratoriais e antropométricos analisados incluíram: peso, estatura, prega cutânea triciptal (PCT), circunferência muscular do braço (CMB), albumina, hematócrito e Kt/V. A gravidade da doença foi avaliada através do índice de gravidade da doença renal (ESRD-SI) e a qualidade de vida (QV) através do Kidney Disease Quality Of Life-Short Form (KDQOL-SF). As médias foram comparadas utilizando teste t de Student e a correlação entre os indicadores antropométricos e a QV foi realizada através do teste de correlação de Pearson, após estratificação por sexo e categorias do ESRD-SI. Foi considerando estatisticamente significante p<0,05. A correlação entre os indicadores nutricionais e QV indicou correlação positiva e significativa entre PCT e QV para os pacientes do sexo masculino com baixo risco de gravidade da doença renal. Houve também correlação positiva entre IMC e QV nos pacientes do sexo masculino com alto risco de gravidade da doença renal, bem como entre PCT e QV nos pacientes do sexo feminino com médio risco da doença renal, porém ambas não significativas. Em conclusão, os resultados encontrados sugerem que o excesso de tecido adiposo possa influenciar positivamente a QV de pacientes hemodialisado
A 155W −95.6 dB THD+N GaN-based Class-D Audio Amplifier With LC Filter Nonlinearity Compensation
No full textSilicon MOSFETs-based medium-power (< 50W) Class-D amplifiers (CDAs) switching in the MHz range have gained popularity in recent years, which achieves better linearity thanks to a higher loop gain in the audio band while enabling the use of LC filters with higher cut-off frequencies. However, for high-power (>100 W) CDAs, such switching frequency and high load current could lead to significant power loss. Furthermore, in the presence of a large current and voltage applied to the load, the linearity of the system can quickly degrade due to LC filter component voltage/current dependency. Without any LC filter nonlinearity compensation technique, LC components with high voltage/current rating must be used to reach high system linearity, which are often expensive and bulky. This paper presents a CDA using a GaN-based output stage to achieve high switching frequency and good efficiency simultaneously, and an integrated controller implemented in a 180nm CMOS technology to compensate for the LC filter nonlinearity. Switching at 1.8 MHz, the CDA can deliver a maximum of 155W from a 50V supply into a load with a peak efficiency of 91.7%. It achieves a peak THD+N of −95.6 dB (0.0017%) while allowing the use of cheaper and smaller nonlinear LC components.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic Components, Technology and MaterialsMicroelectronic
A - 121.5-dB THD Class-D Audio Amplifier With 49-dB LC Filter Nonlinearity Suppression
No full textClass-D audio amplifiers produce electromagnetic interference (EMI), which often needs to be suppressed by an external LC filter. However, due to component nonlinearity, this filter can itself cause significant distortion. This article presents a class-D amplifier that suppresses LC filter nonlinearity by 49 dB and is robust to ±30% variations in its cutoff frequency. This is achieved by a dual-loop architecture, in which an inner loop provides stability, while an outer loop provides the high gain needed to suppress the LC filter and output-stage nonlinearity. A prototype, implemented in a 180-nm BCD process, achieves -121.5-dB total harmonic distortion (THD) and -107.1-dB THD+N, which is maintained to within 3 dB even as the LC filter cutoff frequency is varied from 62 to 106 kHz. It can deliver a maximum of 21 W into a 4-Ω load with 87% efficiency and 12 W into an 8-Ω load with 91% efficiency, measured at 10% THD. Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic InstrumentationMicroelectronic
Multichannel LC ADC: to Record Atrial Electrograms
No full textBiosignals such as electoencephalogram (EEG), electrocorticogram (ECoG), atrial electrogram (AEG) etc. are being recorded from multiple channels simultaneously to improve the spatial resolution of the signals. Conventional multichannel synchronous Analog-to-Digital Converters (ADCs) are used to convert the analog continuous time signals into discrete digital values. Several biosignals have a sparsity in time domain as they have fast-rising peaks in between periods of low activity. Use of conventional synchronous ADCs for conversion of such signals is not an efficient approach as their operation is constant, irrespectiveof the activity of the input signals. Asynchronous ADCs such as level-crossing (LC) ADCs exploit the sparsity of biosignals and thus their operation is activity-dependent. However, multichannel configurations of LC ADCs do not yet exist. This problem is investigated in this work and a new ADC architecture is presented that can combine synchronous sampling with level-crossing quantisation method while converting input signals from several channels simultaneously. The synchronous LC ADC presented in this work achieves 3.37 times reduction in quantisation steps and 6 times reduction in number of output bits generated during conversion of AEG signals as compared to conventional synchronous ADCs. The problem in existing LC ADCs of data overhead in adaptive resolution technique is solved through a novel method named split resolution technique which is also presented in this work.Electrical Engineerin
Practical considerations regarding power factor for nonlinear loads
No full textThis material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of Brunel University's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. Copyright @ 2004 IEEEThe choice of LC compensator may be constrained by the availability of manufacturers units. To account for this, the capacitor values are chosen from among standard values and for each value the transmission losses is minimized, or power factor is maximized, or transmission efficiency is maximized. The global minimum or maximum is obtained by scanning all local minims or maxims. The performance of the obtained compensator is discussed by means of numerical examples
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