Assessment of the energy efficiency estimation methods on induction motors considering real-time monitoring

Different methods have been developed to estimate the energy efficiency of induction motors. The accuracy of these methods vary with the load factor, the unbalanced voltage (UV) and harmonics. The feasibility of these methods for efficiency estimation in real-time were theoretically and experimentally assessed during the operation under different operational conditions (i.e. balanced sinusoidal voltage (BSV), harmonics, UV and harmonics with UV). Results show that for load factors over 80%, the air-gap method is applicable under any condition, while the slip method is only applicable under BSV or balanced harmonic voltage. Moreover, for load factors over 40%, the nameplate method is applicable under BSV. Other methods result in errors over 8% and optimization methods are not applicable for real-time monitoring. Electric systems generally operates with some degree of UV and harmonics, while induction motors mostly operate with load factors below 60%, limiting the use of these methods for real-time measurement

Determinación del peso de reductores mecánicos de un paso utilizando ejes hueco

Los reductores mecánicos son herramientas comúnmente utilizadas para la transmisión de potencia en la industria, constantemente están sometidos a grandes esfuerzos pero a la vez deben ser livianos para acomodarse a las necesidades del medio y uso eficiente de material. El objetivo de este artículo es identificar la incidencia que tendrá la utilización de ejes huecos en el peso de una serie de reductores de transmisión de un paso, para este fin se ha considerado la geometría y variación de peso de cada uno de los elementos constitutivos de los reductores afectados por el cambio geométrico en los árboles de salida, de esta forma se pretende generar un criterio acerca de la conveniencia de utilizar ejes huecos en reductores mecánicos de un paso y cual es su impacto

Environmental assessment of pig production in Cienfuegos, Cuba: Alternatives for manure management

As pork is indispensable in the diet of Cuban people, the government was forced to prioritize its production. Pig production causes several environmental impacts related with air, water and soil pollution, which can be quantified with the application of Life Cycle Assessment that allows to optimize products and processes by identifying their environmental impacts. Farming systems considered in different Life Cycle Assessment studies show substantial differences in their characteristics, namely: animal productivity, feed composition, manure management and production period, which influences the environmental performance of each system. Therefore, each study is unique for the system it assesses and should be analyzed individually. In Cuba, the environmental implications of pig production, whose understanding is cornerstone to eventually adopt more environmentally sound practices while ensuring high productivity standards, are yet to be quantified. This study provides some fundamental insights in the life cycle of pig production in the province of Cienfuegos. The assessment if focused in large farms of the province of Cienfuegos which causes large environmental impacts. Large farms accounts for the production of 77% of the pigs delivered to slaughter houses in the province. Pig production in Cienfuegos accounts for 7-12% of Cuban production. The quantification of the environmental impacts of pig production resulted in an impact per finished pig of 120 kg of live weight of 1892 MJ abiotic depletion of fossil fuels, 1019 kg-CO2-eq. global warming potential, 36 kg 1.4-dichlorobenzene-eq. human toxicity, 17 kg 1.4-dichlorobenzene-eq. terrestrial toxicity, 1 kg 1.4-ethylene-eq. photo-oxidant formation, 12 kg-SO2-eq. acidification potential and 6 kg PO4-eq. eutrophication potential. It appeared that the main opportunities to improve the environmental performance of pig production in Cienfuegos are reduction of the impacts of the anaerobic lagoons used for manure management on global warming potential, acidification potential and eutrophication and the impact on acidification potential of pig housing. Direct land spreading of manure appears as the best alternative to lagooning, considering the current situation of pig breeding in Cienfuegos

Estudio sobre la resistencia y rigidez de ejes huecos

Los ejes son elementos de transmisión que constantemente están sometidos a la acción de cargas y esfuerzos, pero que a la vez deben ser lo suficientemente ligeros para soportar estos sin sacrificar la resistencia mecánica. El objeto de este trabajo es identificar la incidencia que tendrá la reducción de peso en la resistencia mecánica de un eje de transmisión, para este fin se han considerado diversas variaciones geométricas y los resultados se han organizado de forma tal que permitan generar un criterio acerca de la conveniencia de utilizar ejes huecos y cuales serian las geometrías recomendadas

Determinación del peso de reductores mecánicos de un paso utilizando ejes hueco

Los reductores mecánicos son herramientas comúnmente utilizadas para la transmisión de potencia en la industria, constantemente están sometidos a grandes esfuerzos pero a la vez deben ser livianos para acomodarse a las necesidades del medio y uso eficiente de material. El objetivo de este artículo es identificar la incidencia que tendrá la utilización de ejes huecos en el peso de una serie de reductores de transmisión de un paso, para este fin se ha considerado la geometría y variación de peso de cada uno de los elementos constitutivos de los reductores afectados por el cambio geométrico en los árboles de salida, de esta forma se pretende generar un criterio acerca de la conveniencia de utilizar ejes huecos en reductores mecánicos de un paso y cual es su impacto

Mathematical modeling of vertical movement of the upper shaft in cane mills

This study introduces a mathematical model to describe the floating effects of the top roll in sugarcane mills. The model is developed from experimental data measured during the operation of a sugarcane mill. The measured data is fitted using the top shaft rotation period of the mill and dividing on intervals to individually fit each interval obtaining a function defined by parts. The resulting model shows a correlation coefficient of R2 ≥ 0.97. This allow including the floating effect in the study and design of other elements of sugarcane mills

Stress in butt welded joints of open profiles under torsion

In this paper is addressed how in the literature of Mechanic of Materials and Machine Elements Design only few authors address the subject of welded joints, among those can be mentioned Shigley Hall, Reshetov, and Faires [1, 3, 4-5]; although they provide expressions to calculate stress in complex geometric configurations of welded joints, they do not analyze calculation for butt welded joints subject to torsion, neither take into account characteristics of thin-walled side faces for the calculations. Only in the General Treaty of Schimpke Welding, Horn and Ruge [7] are mentioned these features without addressing the expressions for the calculation of stresses in cases of complex cases. Similar case is seen in articles and specialized literature wheredelves into research on the technological parameters in welding, materials and other subjects without addressing the improvement of calculation expressions to determine the stresses in such joints. In this paper new expressions are shown for the calculation of tangential stresses arising on the welds on butt joints of open profiles under free torsion, taking into account thin-wall side faces.En el trabajo se destaca como en la literatura de Mecánica de Materiales y Diseño de Elementos de Máquinas, solo algunos autores abordan el tema de las uniones soldadas, dentro de estos se pueden citar a Shigley, Hall, Reshetov y Faires [1, 3, 4-5]; estos autores, aunque brindan expresiones para el cálculo de las tensiones en uniones soldadas de configuración geométrica compleja, no analizan el cálculo de las mismas para el caso de estar sometidas a torsión, tampoco toman en cuenta para los cálculos las particularidades de los perfiles de paredes delgadas, esto solo es analizado en el Tratado general de soldadura de los autores Schimpke, Horn y Ruge [7], donde se mencionan estas particularidades sin abordar las expresiones para el cálculo de las tensiones en casos complejos. Un tanto similar ocurre en los artículos y literatura especializada, donde se profundiza en la investigación sobre los parámetros tecnológicos en la soldadura, materiales y otros temas sin abordar el perfeccionamiento de las expresiones de cálculo para determinar las tensiones en este tipo de uniones. En el presente trabajo se brindan nuevas expresiones para el cálculo de las tensiones tangenciales que surgen en los cordones de uniones a tope, en perfiles abiertos sometidos a torsión libre, tomando en cuenta para ello su consideración como perfiles de paredes delgadas

The biomass based electricity generation potential of the Province of Cienfuegos, Cuba

By 2013, the province of Cienfuegos in Cuba consumed about 5165 GWh of primary energy, of which an estimated 60 % was used to produce 767 GWh of electricity. 29 % of the primary energy was obtained from renewable fuel, and only less than 5 % of the biomass energy, was used to produce about 27 GWh of biomass based electricity. This study proposes and assesses opportunities to produce electricity from biomass in the sugar industry of the province. The scenarios considered include: upgrading the agricultural yield of sugarcane, producing energy cane and combusting it after the sugarcane milling season, combusting the filter cake, combusting marabu (Dichrostachys cinerea, a bush tree considered a plague in Cuba) after the sugarcane milling season, and updating the electricity generation technology. Results are given for the different scenarios and it is shown that a combined scenario, including upgrading agricultural yield of sugarcane, upgrading electricity generation technology, combusting filter cake, and producing energy cane to generate electricity after the sugarcane milling season, thus allowing to use the generation units in sugar factories during 8000 h per year affords a potential production of 1150 GWh of electricity, 50 % more than consumed in Cienfuegos province in 2013. © 2016, Springer Science+Business Media Dordrecht