Transient harmonic torques in induction machines: measurement and impact on motor performance

This paper focuses on the measurement of transient torques produced by the field harmonics in three phase squirrel cage motors and on the assessment of the operating conditions under which these torques might become significant. The paper presents first a model of the induction machine with any stator and rotor phase number and configuration, fed by arbitrary voltage waveforms and taking into account the space harmonics. Then, very much attention is paid to a reliable model validation against actual transient torques measurements. In this sense, the actual and great difficulties of measuring pulsating electromagnetic torques of several hundreds of Hertz are brought into light, the possible measurement techniques are critically reviewed and the solution chosen is discussed. Once the model accuracy has been experimentally confirmed, it is used to carry out a systematic plan of more than 250 simulations under clearly distinct operating conditions on five different motors. The analysis of these simulations yields a main practical conclusion: field harmonics may have (depending on the motor structure) a significant impact on electromagnetic torque, but only during transients characterized by high instantaneous frequencies of the rotor currents. For low slip transients, their impact is negligible. This conclusion is also theoretically justified in the paper.Echeverria Villar, JA.; Martínez-Román, J.; Serrano Iribarnegaray, L. (2012). Transient harmonic torques in induction machines: measurement and impact on motor performance. Electrical Engineering. 94(2):67-80. doi:10.1007/s00202-011-0216-4S6780942White D, Woodson H (1959) Electromechanical energy conversion. Wiley, LondonTaegen F, Hommes E (1972) Das allgemeine Gleichungssystem des Käfigläufermotors unter Berücksichtigung der Oberfelder. Teil I and II. Archiv für Elektrotechnik 55:21–31 and 98–105Van der Merwe FS (1976) The analysis of an electric machine with a smooth air-gap allowing for all winding MMF harmonics. Parts I and II. Archiv für Elektrotechnik 58:283–292 and 293–303Fudeh HR, Ong CM (1983) Modeling and analysis of induction machines containing space harmonics. Parts I, II and III. IEEE Trans Power Apparatus Syst PAS-102(8):2608–2615; 2616–2620; 2621–2628Hommes E, Paap GC (1984) The analysis of the 3-phase squirrel cage induction motor with space harmonics. Part 1 and 2. Archiv für Elektrotechnik 67:217–226 and 227–236Heller B, Hamata V (1977) Harmonic field effects in induction machines. Elsevier Scientific Publishing Co, AmsterdamSeinsch HO (1992) Oberfelderscheinungen in Drehfeldmaschinen. B.G. Teubner, SuttgartOberretl K (2007) Losses, torques and magnetic noise in induction motors with static converter supply, taking multiple armature reaction and slot opening into account. IET Electr Power Appl 1(4): 517–531Levi E, Bojoi R, Profumo F, Tolyat HA, Williamson S (2007) Multiphase induction motor drives. A technology status review. IET Electr Power Appl 1(4): 489–516Park RH (1933) Two-Reaction theory of synchronous machines. A.I.E.E. Trans 48:716–730, 1929 and 52:352–355Wallin C, Ling H, Rasool A (2001) Evaluation of torque pulses in industrial applications using the torque sensor TorductorR-s presented at Sensor for Industry conference. Illinois, USANCTE (2011) High dynamic, non contact, rotary torque sensor—Series 2000. http://www.ncte.de/ncte/cms/front_content.php?idcat=27Hübner Berlin (2002) Acc. sensor ACC93, Preliminary leafletDenne A, Rausch H, Freise W (1981) Aufnehmer zur Messung schnell veränderlicher Drehbeschleunigungen und Drehmomente. Technisches-Messen-tm 48: 339–342Hillner L (2002) Hübner Berlin. Notes about ACC93 installation in motor ABB M2AA112 M-4 from Universidad Politecnica de ValenciaSerrano-Iribarnegaray L, Martínez-Román J (2005) Critical review of the analytical approaches accounting for interbar currents and experimental study of ageing in two-speed asynchr. motors for elevator drives. IEE Proc Electr Power Appl 152: 72–80Echeverría-Villar JA (2004) Aplicación de la teoría de los fasores espaciales al estudio de los campos armónicos en los regímenes transitorios de las máquinas asíncronas y sus repercusiones en los pares pulsantes. PhD Th.; Universidad Politécnica de ValenciaOberretl K (1994) Parasitäre synchrone Dreh- und Pendelmomente in Asynchronmotoren. Einfluss von Ausgleichsvorgängen und Eisensättigung. Parts I and II. Archiv für Elektrotechnik 77:179–190 and 277–288Oberretl K (1965) Ueber den Einfluss von parallelen Wicklungs- zweigen, Dreieckschaltung, Spulensehnung. Nutzschlitzbreite und Nutenschrägung auf das Drehmoment von Käfigläufermotoren in ETZ-A Bd 86: 619–627Brüderlin R (1921) Ueber eine graphische Zerlegung der Feld-Erregerkurve einer unregelmässigen Mehrphasenwicklung in ihre Einzelwellen. ETZ-Archiv für Elektrotechnik 42: 1093–1096Köhler G, Walther A (1931) Fouriersche Analyse von Funktionen mit Sprüngen, Ëcken und änlichen Besonderheiten. Archiv für Elektrotechnik 25: 747–755Lax F, Jordan H (1940) Über die Fourier-Entwicklung der Felderregerkurve von schrittverkürzen Drehstromwicklungen beliebiger Phasenzhal. Archiv für Elektrotechnik 34: 591–597Stepina J (1979) Einführung in die allgemeine Raumzeiger Theorie der elektrischen Maschinen. Press of University of Kaiserslauter

Periodontal diseases: is it possible to prevent them? A populational and individual approach

Periodontal diseases are infectious inflammatory chronic diseases of a multifactorial nature. They are primarily caused by dysbiotic ecological changes in dental biofilm, which may be influenced by risk factors. The prevention of periodontal diseases may involve different strategies focused on reducing distal, intermediate, and proximal risk factors at both the population and individual levels. Effective prevention depends on interdisciplinary and common risk factor approaches. Also, patient-centered preventive models are more effective than professional-centered models in the management of periodontal diseases. Regular and periodic control of dental biofilm is an essential measure for the different levels of prevention of periodontal diseases. The effectiveness of periodontal disease prevention largely depends on positive modifications of behavior, knowledge, health literacy, patient empowerment, motivation, and compliance.publishedVersio

Recerca i tecnologia en enginyeria gràfica i disseny a la Universitat Politècnica de Catalunya

Els temps canvien cada vegada més ràpidament, i a la universitat això encara es nota més. L’històric departament d‘Expressió Gràfica a l’Enginyeria (EGE) de la Universitat Politècnica de Catalunya, garant d’una docència de Grau, Màster i Doctorat de qualitat i adaptada a les necessitats de la societat, emprèn l’any 2020 amb una proposta de canvi de nom per adaptar-se al nous coneixements que estan esdevenint la seva matèria principal, al voltant de l’enginyeria gràfica i el disseny. Les àrees de recerca del centenar de professors que formen el departament són àmplies i variades, i sempre en col·laboració en diversos grups tant de la pròpia UPC com d’altres universitats. Una recerca avançada, de caràcter pluridisciplinari, on s'apliquen creativitat i innovació com a eines de coneixement, implicats en un territori ampli, i situats als diferents campus de la UPC. En els capítols d’aquest llibre podeu veure una petita mostra d’aquesta recerca tecnològica en camps ben variats.Postprint (published version

European Red List of Trees

The European Red List is a review of the status of European species according to IUCN regional Red Listing guidelines. It identifies those species that are threatened with extinction at the regional level – in order that appropriate conservation action can be taken to improve their status. This publication summarises results for all Europe’s native species of tree (454 species), of which 265 species (over 58%) are endemic to continental Europe, with 56% (252 species) endemic to the 28 EU Member States. Of these, 168 (42%) of the species are threatened with extinction at the European level, however, for 57 species (nearly 13%) there was insufficient information to assign a conservation status, and are therefore classified as Data Deficient, and in need of further research. The main threat to tree species in Europe has been identified as invasive or problematic species, impacting 38% of tree species, followed by deforestation and wood harvesting, and urban development (both affecting 20% of tree species). For threatened species, livestock farming, land abandonment, changes in forest and woodland management, and other ecosystem modifications such as fire are the major threats, impacting the survival of trees.Peer reviewe

Effects of intubation timing in patients with COVID-19 throughout the four waves of the pandemic : a matched analysis

The primary aim of our study was to investigate the association between intubation timing and hospital mortality in critically ill patients with COVID-19-associated respiratory failure. We also analysed both the impact of such timing throughout the first four pandemic waves and the influence of prior non-invasive respiratory support on outcomes. This is a secondary analysis of a multicentre, observational and prospective cohort study that included all consecutive patients undergoing invasive mechanical ventilation due to COVID-19 from across 58 Spanish intensive care units (ICU) participating in the CIBERESUCICOVID project. The study period was between 29 February 2020 and 31 August 2021. Early intubation was defined as that occurring within the first 24 h of intensive care unit (ICU) admission. Propensity score (PS) matching was used to achieve balance across baseline variables between the early intubation cohort and those patients who were intubated after the first 24 h of ICU admission. Differences in outcomes between early and delayed intubation were also assessed. We performed sensitivity analyses to consider a different timepoint (48 h from ICU admission) for early and delayed intubation. Of the 2725 patients who received invasive mechanical ventilation, a total of 614 matched patients were included in the analysis (307 for each group). In the unmatched population, there were no differences in mortality between the early and delayed groups. After PS matching, patients with delayed intubation presented higher hospital mortality (27.3% versus 37.1%, p =0.01), ICU mortality (25.7% versus 36.1%, p=0.007) and 90-day mortality (30.9% versus 40.2%, p=0.02) when compared to the early intubation group. Very similar findings were observed when we used a 48-hour timepoint for early or delayed intubation. The use of early intubation decreased after the first wave of the pandemic (72%, 49%, 46% and 45% in the first, second, third and fourth wave, respectively; first versus second, third and fourth waves p<0.001). In both the main and sensitivity analyses, hospital mortality was lower in patients receiving high-flow nasal cannula (n=294) who were intubated earlier. The subgroup of patients undergoing NIV (n=214) before intubation showed higher mortality when delayed intubation was set as that occurring after 48 h from ICU admission, but not when after 24 h. In patients with COVID-19 requiring invasive mechanical ventilation, delayed intubation was associated with a higher risk of hospital mortality. The use of early intubation significantly decreased throughout the course of the pandemic. Benefits of such an approach occurred more notably in patients who had received high-flow nasal cannul

European Guidelines on Cardiovascular Disease Prevention in Clinical Practice: CEIPC 2008 Spanish adaptation

Basado en el Documento del Cuarto Grupo de Trabajo Conjunto de la Sociedad Europea de Cardiología y otras sociedades científicas: Graham I, Atar D, Borch-Johnsen K, Boysen G, Burell G, Cifkova R, et al et al. European guidelines on cardiovascular disease prevention in clinical practice: fourth joint Task Force of the European Society of Cardiology and Other Societies on Cardiovascular Disease Prevention in Clinical Prevention in Clinical Practice (constituted by representatives of nine societies and by invited experts). Eur J Cardiovasc Prev Rehabil 2007; 28: 2375 2414.We present the Spanish adaptation from the CEIPC of the European Guidelines on Cardiovascular Disease Prevention in Clinical Practice 2008. This guide recommends the SCORE model for risk evaluation. The aim is to prevent premature mortality and morbidity due to CVD by means of dealing with its related risk factors in clinical practice. The guide focuses on primary prevention and emphasizes the role of the nurses and primary care medical doctors in promoting a healthy life style, based on increasing physical activity, change dietary habits, and non smoking. The therapeutic goal is to achieve a Blood Pressure <140/90 mmHg, but among patients with diabetes, chronic kidney disease, or definite CVD, the objective is <130/80 mmHg. Serum cholesterol should be <200 mg/dl and cLDL <130 mg/dl, although among patients with CVD or diabetes, the objective is <100 mg/dl (80 mg/dl if feasible in very high-risk patients). Patients with type 2 diabetes and those with metabolic syndrome must lose weight and increase their physical activity, and drugs must be administered whenever applicable, with the objective guided by BMI -body mass index- and waist circumference. In diabetic type 2 patients, the objective is glycated haemoglobin <7%. Allowing people to know the guides and developing implementation programs, identifying barriers and seeking solutions for them, are priorities for the CEIPC in order to put the recommendations into practice.S

Global maps of soil temperature

Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km2 resolution for 0–5 and 5–15 cm soil depth. These maps were created by calculating the difference (i.e. offset) between in situ soil temperature measurements, based on time series from over 1200 1-km2 pixels (summarized from 8519 unique temperature sensors) across all the world\u27s major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (−0.7 ± 2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications