Torque vibration model of axial-flux surface-mounted permanent magnet synchronous machine

In order that the radius and thus ununiform structure of the teeth and otherelectrical and magnetic parts of the machine may be taken into consideration the calculation of an axial flux permanent magnet machine is, conventionally, doneby means of 3D FEM-methods. This calculation procedure, however, requires a lotof time and computer recourses. This study proves that also analytical methods can be applied to perform the calculation successfully. The procedure of the analytical calculation can be summarized into following steps: first the magnet is divided into slices, which makes the calculation for each section individually, and then the parts are submitted to calculation of the final results. It is obvious that using this method can save a lot of designing and calculating time. Thecalculation program is designed to model the magnetic and electrical circuits of surface mounted axial flux permanent magnet synchronous machines in such a way, that it takes into account possible magnetic saturation of the iron parts. Theresult of the calculation is the torque of the motor including the vibrations. The motor geometry and the materials and either the torque or pole angle are defined and the motor can be fed with an arbitrary shape and amplitude of three-phase currents. There are no limits for the size and number of the pole pairs nor for many other factors. The calculation steps and the number of different sections of the magnet are selectable, but the calculation time is strongly depending on this. The results are compared to the measurements of real prototypes. The permanent magnet creates part of the flux in the magnetic circuit. The form and amplitude of the flux density in the air-gap depends on the geometry and material of the magnetic circuit, on the length of the air-gap and remanence flux density of the magnet. Slotting is taken into account by using the Carter factor in the slot opening area. The calculation is simple and fast if the shape of the magnetis a square and has no skew in relation to the stator slots. With a more complicated magnet shape the calculation has to be done in several sections. It is clear that according to the increasing number of sections also the result will become more accurate. In a radial flux motor all sections of the magnets create force with a same radius. In the case of an axial flux motor, each radial section creates force with a different radius and the torque is the sum of these. The magnetic circuit of the motor, consisting of the stator iron, rotor iron, air-gap, magnet and the slot, is modelled with a reluctance net, which considers the saturation of the iron. This means, that several iterations, in which the permeability is updated, has to be done in order to get final results. The motor torque is calculated using the instantaneous linkage flux and stator currents. Flux linkage is called the part of the flux that is created by the permanent magnets and the stator currents passing through the coils in stator teeth. The angle between this flux and the phase currents define the torque created by the magnetic circuit. Due to the winding structure of the stator and in order to limit the leakage flux the slot openings of the stator are normally not made of ferromagnetic material even though, in some cases, semimagnetic slot wedges are used. In the slot opening faces the flux enters the iron almost normally (tangentially with respect to the rotor flux) creating tangential forces in the rotor. This phenomenon iscalled cogging. The flux in the slot opening area on the different sides of theopening and in the different slot openings is not equal and so these forces do not compensate each other. In the calculation it is assumed that the flux entering the left side of the opening is the component left from the geometrical centre of the slot. This torque component together with the torque component calculated using the Lorenz force make the total torque of the motor. It is easy to assume that when all the magnet edges, where the derivative component of the magnet flux density is at its highest, enter the slot openings at the same time, this will have as a result a considerable cogging torque. To reduce the cogging torquethe magnet edges can be shaped so that they are not parallel to the stator slots, which is the common way to solve the problem. In doing so, the edge may be spread along the whole slot pitch and thus also the high derivative component willbe spread to occur equally along the rotation. Besides forming the magnets theymay also be placed somewhat asymmetric on the rotor surface. The asymmetric distribution can be made in many different ways. All the magnets may have a different deflection of the symmetrical centre point or they can be for example shiftedin pairs. There are some factors that limit the deflection. The first is that the magnets cannot overlap. The magnet shape and the relative width compared to the pole define the deflection in this case. The other factor is that a shifting of the poles limits the maximum torque of the motor. If the edges of adjacent magnets are very close to each other the leakage flux from one pole to the other increases reducing thus the air-gap magnetization. The asymmetric model needs some assumptions and simplifications in order to limit the size of the model and calculation time. The reluctance net is made for symmetric distribution. If the magnets are distributed asymmetrically the flux in the different pole pairs will not be exactly the same. Therefore, the assumption that the flux flows from the edges of the model to the next pole pairs, in the calculation model from one edgeto the other, is not correct. If it were wished for that this fact should be considered in multi-pole pair machines, this would mean that all the poles, in other words the whole machine, should be modelled in reluctance net. The error resulting from this wrong assumption is, nevertheless, irrelevant.

Eettiset sijoitusrahastot Suomessa – Nykytilan arviointi

Tutkimus eettiset sijoitusrahastot Suomessa – nykytilan arviointi, on kvalitatiivinen, teorialähtöinen kirjallisuustutkimus, jossa selvitetään eettisten sijoitusrahastojen nykytilannetta Suomessa. Päätavoitteena on selvittää, mitä ja minkälaisia eettiset sijoitusrahastot ovat Suomessa. Alatavoitteena tutkitaan myös eettisten rahastojen kehitystä niin Suomessa kuin kansainvälisestikin. Tutkimuksessa on kartoitettu Suomessa toimivat eettiset sijoitusrahastot ja vertailtu niitä keskenään sekä selvitetty niiden sijoituspolitiikkaa ja toimintaa. Aineistona on käytetty tieteellisen kirjallisuuden lisäksi pankkien ja pankkiiriliikkeiden aineistoja. Tutkimus on tehty kirjallisuuden pohjalta ja tutkimus perustuu kirjallisuuden ja tutkimusaineiston analysointiin sekä siitä tehtäviin johtopäätöksiin. Tutkimuksessa havaittiin, että suomalaiset eettisiksi luokiteltavat rahastot ovat hyvin identtisiä ja niissä näkyy vahva painotus ympäristöön ja ilmastoon. Eettisten rahastojen määrä ja koko on kasvanut nopeasti koko 2000 – luvun ja tutkimuksen tekovaiheessa Suomessa toimii 22 eri eettistä rahastoa ja näiden yhteenlaskettu rahastopääoma on noin 5,8 Mrd. euroa, joka on noin 8 % koko rahastopääomasta (66 Mrd. euroa, (2007)) Suomessa eettinen sijoittaminen on vielä suhteellisen uusi ilmiö ja kansainvälisesti vertailtuna eettinen sijoittaminen on toistaiseksi pientä.

Process intensification: From optimised flow patterns to microprocess technology

This thesis is focused on process intensification. Several significant problems and applications of this theme are covered. Process intensification is nowadays one of the most popular trends in chemical engineering and attempts have been made to develop a general, systematic methodology for intensification. This seems, however, to be very difficult, because intensified processes are often based on creativity and novel ideas. Monolith reactors and microreactors are successful examples of process intensification. They are usually multichannel devices in which a proper feed technique is important for creating even fluid distribution into the channels. Two different feed techniques were tested for monoliths. In the first technique a shower method was implemented by means of perforated plates. The second technique was a dispersion method using static mixers. Both techniques offered stable operation and uniform fluid distribution. The dispersion method enabled a wider operational range in terms of liquid superficial velocity. Using dispersion method, a volumetric gas-liquid mass transfer coefficient of 2 s-1 was reached. Flow patterns play a significant role in terms of the mixing performance of micromixers. Although the geometry of a T-mixer is simple, channel configurations and dimensions had a clear effect on mixing efficiency. The flow in the microchannel was laminar, but the formation of vortices promoted mixing in micro T-mixers. The generation of vortices was dependent on the channel dimensions, configurations and flow rate. Microreactors offer a high ratio of surface area to volume. Surface forces and interactions between fluids and surfaces are, therefore, often dominant factors. In certain cases, the interactions can be effectively utilised. Different wetting properties of solid materials (PTFE and stainless steel) were applied in the separation of immiscible liquid phases. A micro-scale plate coalescer with hydrophilic and hydrophobic surfaces was used for the continuous separation of organic and aqueous phases. Complete phase separation occurred in less than 20 seconds, whereas the separation time by settling exceeded 30 min. Fluid flows can be also intensified in suitable conditions. By adding certain additives into turbulent fluid flow, it was possible to reduce friction (drag) by 40 %. Drag reduction decreases frictional pressure drop in pipelines which leads to remarkable energy savings and decreases the size or number of pumping facilities required, e.g., in oil transport pipes. Process intensification enables operation often under more optimal conditions. The consequent cost savings from reduced use of raw materials and reduced waste lead to greater economic benefits in processing.

Russia, China, India Foresight for Small and Medium size Enterprises in Uusimaa : Changes forecast in the Russian, Chinese and Indian operating environments from the viewpoint of small and middle-sized enterprises in Uusimaa

The report describes those factors of the future that are related to the growth and needs of Russia, China, and India and that may provide significant internationalisation potential for Uusimaa companies. The report examines the emerging trends and market-entry challenges for each country separately. Additionally, it evaluates the training needs of Uusimaa companies in terms of the current offerings available for education on topics related to Russia, China, and India. The report was created via the Delphi method: experts were interviewed, and both Trendwiki material and the latest literature were used to create a summary of experts’ views, statements, and reasons behind recent developments. This summary of views was sent back to the experts with the objective of reaching consensus synthesising the differing views or, at least, of providing argumentation for the various alternative lines of development. In addition to a number of outside experts and business leaders, all heads of Finpro’s Finland Trade Centers participated in the initial interviews. The summary was commented upon by all Finpro consultants and analysts for Russia, China, and India, with each focusing on his or her own area of expertise. The literature used consisted of reports, listed for each country, and an extensive selection of the most recent newspaper articles. The report was created in January-April 2010. On 22 April 2010 its results were reviewed at the final report presentation in cooperation with the Uusimaa ELY Centre.