Study of the Thermal Behavior of a Three-phase Induction Motor under Fault Conditions

Electric motors play an important role in the industry, because nowadays almost everything in the industry works with the auxiliary of them, either for low or high power ratings. It is possible to divide the electric motors in induction motors and synchronous motors, however the most used in the industry are the induction motors. So, it is very important to monitor its behavior throughout the time. Due to their working conditions, which sometimes can be very adverse, the motor losses can increase the inner machine temperature causing degradation of the materials which will lead to serious faults. Most severe faults may lead to a machine breakdown and interruption of the industrial production inflicting severe financial loss. The main goal of this dissertation is to create a computational model of a three-phase squirrel cage induction motor to study and analyze its thermal behavior under healthy and faulty conditions. This will be made through the finite elements method (FEM), where Flux2D 12.1 (Cedrat) software will be used. Initially the computational modeling will focus on the electromagnetic study, in order to calculate the motor losses. After that, those values will be inserted in the thermal simulation to better understand the thermal behavior of the motor. The experimental tests will be carried out with the aid of five temperature sensors (PT100), where the acquisition of the experimental data will be done through a software developed in LabView programming language. As well as that, the results obtained experimentally will be compared with those obtained computationally. However, only the results of two sensors can be compared, since two of them are placed throughout the three-dimensional perspective of the motor and one is placed inner of the motor frame, which will not be defined in the simulation.Os motores elétricos desempenham um papel bastante importante na indústria, pois hoje em dia quase tudo na indústria funciona com o auxílio destes, seja em reduzidas ou elevadas potências. É possível dividir os motores elétricos em motores de indução e motores síncronos, no entanto os mais utilizados na indústria são os de indução, sendo então bastante importante monitorizar o seu comportamento ao longo do tempo. Devido às suas condições de funcionamento, que por vezes são bastante adversas, as perdas do motor podem aumentar causando a degradação dos materiais e levando a falhas graves, que podem prejudicar toda a produção de uma indústria, infligindo graves perdas financeiras O objetivo principal desta dissertação é criar um modelo computacional de um motor de indução trifásico de rotor em gaiola de esquilo para estudar e analisar o seu comportamento térmico, tanto sob condições normais como de avaria. Este trabalho será desenvolvido através do método de elementos finitos (FEM), sendo assim utilizado o software Flux2D 12.1 (Cedrat). Inicialmente a modelação computacional focar-se-á no estudo eletromagnético, de forma a calcularem-se as perdas do motor. Posteriormente, esses valores serão inseridos na simulação térmica, de forma a compreender-se melhor o comportamento térmico do motor. Os ensaios experimentais terão o auxílio de cinco sensores de temperatura (PT100) onde a aquisição dos dados experimentais é efetuada através de um software desenvolvido na linguagem de programação LabView. Posteriormente, os resultados obtidos experimentalmente serão comparados com os resultados obtidos computacionalmente. Porém, apenas os resultados de dois dos sensores podem ser comparados, pois existem dois sensores ao longo da perspetiva tridimensional do motor e um que está situado na periferia interna da carcaça, a qual não será definida na simulação

Geoeconomic variations in epidemiology, ventilation management, and outcomes in invasively ventilated intensive care unit patients without acute respiratory distress syndrome: a pooled analysis of four observational studies

Background: Geoeconomic variations in epidemiology, the practice of ventilation, and outcome in invasively ventilated intensive care unit (ICU) patients without acute respiratory distress syndrome (ARDS) remain unexplored. In this analysis we aim to address these gaps using individual patient data of four large observational studies. Methods: In this pooled analysis we harmonised individual patient data from the ERICC, LUNG SAFE, PRoVENT, and PRoVENT-iMiC prospective observational studies, which were conducted from June, 2011, to December, 2018, in 534 ICUs in 54 countries. We used the 2016 World Bank classification to define two geoeconomic regions: middle-income countries (MICs) and high-income countries (HICs). ARDS was defined according to the Berlin criteria. Descriptive statistics were used to compare patients in MICs versus HICs. The primary outcome was the use of low tidal volume ventilation (LTVV) for the first 3 days of mechanical ventilation. Secondary outcomes were key ventilation parameters (tidal volume size, positive end-expiratory pressure, fraction of inspired oxygen, peak pressure, plateau pressure, driving pressure, and respiratory rate), patient characteristics, the risk for and actual development of acute respiratory distress syndrome after the first day of ventilation, duration of ventilation, ICU length of stay, and ICU mortality. Findings: Of the 7608 patients included in the original studies, this analysis included 3852 patients without ARDS, of whom 2345 were from MICs and 1507 were from HICs. Patients in MICs were younger, shorter and with a slightly lower body-mass index, more often had diabetes and active cancer, but less often chronic obstructive pulmonary disease and heart failure than patients from HICs. Sequential organ failure assessment scores were similar in MICs and HICs. Use of LTVV in MICs and HICs was comparable (42·4% vs 44·2%; absolute difference -1·69 [-9·58 to 6·11] p=0·67; data available in 3174 [82%] of 3852 patients). The median applied positive end expiratory pressure was lower in MICs than in HICs (5 [IQR 5-8] vs 6 [5-8] cm H2O; p=0·0011). ICU mortality was higher in MICs than in HICs (30·5% vs 19·9%; p=0·0004; adjusted effect 16·41% [95% CI 9·52-23·52]; p<0·0001) and was inversely associated with gross domestic product (adjusted odds ratio for a US$10 000 increase per capita 0·80 [95% CI 0·75-0·86]; p<0·0001). Interpretation: Despite similar disease severity and ventilation management, ICU mortality in patients without ARDS is higher in MICs than in HICs, with a strong association with country-level economic status