Modeling and evaluation of laminated windings

Electrical machines in electrical vehicles are sometimes put under a lot of stress when for example climbing an uphill road. In order for the machine to cope with the heat generation that comes of running extended periods of time near or at peak power one needs a highly developed cooling system. At the division of Industrial Electrical Engineering and Automation (IEA), located at Lunds Tekniska Högskola (LTH), a new and innovative winding design is developed which make cooling the machine more efficient. The winding consists of a laminated sheet which is rolled in a spiral. There is a small space between each winding turn making it possible for an air stream to flow through cooling the conductive sheets. The cooling capabilities of such design are evaluated throughout this thesis. Measurements are performed on two prototype winding built at IEA. The measurement rig are built solely for this purpose mainly in order to maintain the right measurement, a great deal of time during the thesis is put on perfecting the rig. Beside measurements are numerical models of the winding built in Comsol Multiphysics, both in 2 and 3 dimensions. Besides numerical modeling is an analytical model built with help of Matlab. The analytical model is used, among else, to simulate transient conditions and drive cycle analysis of an electrical machine suited for a bus. Results from simulations and measurement show that the laminated winding is able to cope with high amounts current without harm due to the effective cooling. Simulations show an ability to use current densities in the winding stretching towards 30 A/mm2 and still are able to keep tolerable temperatures. Results also point out weaknesses in the winding construction in form of sensitivity to winding geometries of certain type as well as unevenly spaced winding turns. Ways to improve the cooling performance of the winding by altering the geometry and improving the construction process are discussed in this thesis. The electrical machines used today are often oversized in order to thermally handle the periods of excessive power need. The effectiveness of such a machine is best during these short stretches of high power output even if they nominally are driven at a much lower power where the effectiveness is worse. The laminated winding design enables the use of smaller machines with peak efficiency at nominal drive that still are able to cope the periods of extreme power need due to the effective cooling

Selecting Cutting Data Tests for Cutting Data Modeling Using the Colding Tool Life Model

An analysis on selecting cutting speed, cutting feed and depth of cut when collecting data for the Colding Tool Life Model based on Woxen's Equivalent Chip Thickness was performed to achieve the lowest possible model error. All possible combinations of a large data set were evaluated with regard to model error. This work shows that an increase of ratio between the highest and lowest cutting speed, feed, depth of cut and tool life within the five included tool life tests increases the likelihood of an accurate model. Further, to ensure an accurate model, it is not enough to have a large ratio of one single parameter, but a large ratio in all parameters is needed. The paper also presents a suggestion on how to select the cutting data points, derived from the best performing tool life models. It is concluded that one should aim to have one pair of cutting data points with equal equivalent chip thickness while varying cutting speed and three more test points with different equivalent chip thickness

Effects of reindeer grazing and forestry on ground lichens in Finnish Lapland.

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Poron laidunnuksen ja metsätalouden vaikutukset maajäkäliin

TutkimusselosteSeloste artikkelista: Akujärvi, A., Hallikainen, V., Hyppönen, M., Mattila, E., Mikkola, K. & Rautio, P. 2014. Effects of reindeer grazing and forestry on ground lichens in Finnish Lapland. Silva Fennica 48(3), article id 1153

Sources and sinks of greenhouse gases in the landscape : Approach for spatially explicit estimates

Climate change mitigation is a global response that requires actions at the local level. Quantifying local sources and sinks of greenhouse gases (GHG) facilitate evaluating mitigation options. We present an approach to collate spatially explicit estimated fluxes of GHGs (carbon dioxide, methane and nitrous oxide) for main land use sectors in the landscape, to aggregate, and to calculate the net emissions of an entire region. Our procedure was developed and tested in a large river basin in Finland, providing information from intensively studied eLTER research sites. To evaluate the full GHG balance, fluxes from natural ecosystems (lakes, rivers, and undrained mires) were included together with fluxes from anthropogenic activities, agriculture and forestry. We quantified the fluxes based on calculations with an anthropogenic emissions model (FRES) and a forest growth and carbon balance model (PREBAS), as well as on emission coefficients from the literature regarding emissions from lakes, rivers, undrained mires, peat extraction sites and cropland. Spatial data sources included CORINE land use data, soil map, lake and river shorelines, national forest inventory data, and statistical data on anthropogenic activities. Emission uncertainties were evaluated with Monte Carlo simulations. Artificial surfaces were the most emission intensive land-cover class. Lakes and rivers were about as emission intensive as arable land. Forests were the dominant land cover in the region (66%), and the C sink of the forests decreased the total emissions of the region by 72%. The region's net emissions amounted to 4.37 +/- 1.43 Tg CO2-eq yr(-1), corresponding to a net emission intensity 0.16 Gg CO2-eq km(-2) yr(-1), and estimated per capita net emissions of 5.6 Mg CO2-eq yr(-1). Our landscape approach opens opportunities to examine the sensitivities of important GHG fluxes to changes in land use and climate, management actions, and mitigation of anthropogenic emissions. (C) 2021 The Authors. Published by Elsevier B.V.peerReviewe

Cryogenic and hybrid induction-assisted machining strategies as alternatives for conventional machining of refractory tungsten and niobium

Tungsten (W) and niobium (Nb) belong to the refractory metal group and are used as alloying elements in steels and superalloys for high demand products. These metals are also used in a high purity single-phase state for products within nuclear, space, military and research facilities.In the current study, tool wear development and surface quality at different cutting conditions have been evaluated when machining high purity W 99.95% and Nb 99.7% in longitudinal turning. Cryogenic LN2 cooling and hybrid induction-assisted machining strategies were applied in order to alter W and Nb material state with respect to the ductile-to-brittle transformation temperature, and thus to attempt controlling their machinability. These advanced machining strategies were benchmarked against the more conventional machining solutions of dry, flood and high pressure cooling.It was found that the use of LN2 cooling demonstrated the best result in terms of tool life when machining W followed by induction-assisted heating, dry and flood. All machining strategies provided similar surface quality which is related to strong build-up edge formation and respective surface alteration. When machining Nb, high pressure coolant results in best performance in terms of tool life and surface quality, then followed by flood and cryogenic strategies. Overall, substantial improvement of surface quality (Ra = 0.4–0.6 μm) was observed for high cutting speeds vc ≥ 225 m/min

Metsätalouden ja porotalouden vaikutukset maajäkälien määrään

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Poron laidunnuksen ja metsätalouden vaikutukset maajäkäliin

201

Mapping of magnetic properties for simulations of high-Temperature electromagnetic applications

Purpose -The purpose of this paper is to investigate the added value of using temperature-dependent electric and magnetic properties in high-Temperature electromagnetic simulations. Design/methodology/approach - In this work, the electromagnetic properties of Domex 420, SSAB, have been characterized as a function of the temperature, from room temperature to 900°C. The measurement of the electric and magnetic properties was performed inside a vacuum furnace at a number of discrete temperature steps, with particularly small intervals around the Curie temperature. A simple transient multi-physics model was used to investigate the impact of the measured properties in three different representations. Findings - In certain intervals, a simplified approximation of the properties produces accurate results, while fully parametric representation is beneficial when heating above the Curie temperature. Originality/value -Temperature-dependent electromagnetic properties are rarely found, especially in an easy-To-use form. Using parameterized temperature-dependent approximation of key properties shows noteworthy differences in the outcome of high-Temperature electromagnetic modeling