High-Speed Solid-Rotor Induction Machine – Electromagnetic Calculation and Design

Within the latest decade high-speed motor technology has been increasingly commonly applied within the range of medium and large power. More particularly, applications like such involved with gas movement and compression seem to be the most important area in which high-speed machines are used. In manufacturing the induction motor rotor core of one single piece of steel it is possible to achieve an extremely rigid rotor construction for the high-speed motor. In a mechanical sense, the solid rotor may be the best possible rotor construction. Unfortunately, the electromagnetic properties of a solid rotor are poorer than the properties of the traditional laminated rotor of an induction motor. This thesis analyses methods for improving the electromagnetic properties of a solid-rotor induction machine. The slip of the solid rotor is reduced notably if the solid rotor is axially slitted. The slitting patterns of the solid rotor are examined. It is shown how the slitting parameters affect the produced torque. Methods for decreasing the harmonic eddy currents on the surface of the rotor are also examined. The motivation for this is to improve the efficiency of the motor to reach the efficiency standard of a laminated rotor induction motor. To carry out these research tasks the finite element analysis is used. An analytical calculation of solid rotors based on the multi-layer transfer-matrix method is developed especially for the calculation of axially slitted solid rotors equipped with wellconducting end rings. The calculation results are verified by using the finite element analysis and laboratory measurements. The prototype motors of 250 – 300 kW and 140 Hz were tested to verify the results. Utilization factor data are given for several other prototypes the largest of which delivers 1000 kW at 12000 min-1.

Trigger and data link system for CMS Resistive Plate Chambers at the LHC accelerator

The purpose of the work was to realize a high-speed digital data transfer system for RPC muon chambers in the CMS experiment on CERN’s new LHC accelerator. This large scale system took many years and many stages of prototyping to develop, and required the participation of tens of people. The system interfaces to Frontend Boards (FEB) at the 200,000-channel detector and to the trigger and readout electronics in the control room of the experiment. The distance between these two is about 80 metres and the speed required for the optic links was pushing the limits of available technology when the project was started. Here, as in many other aspects of the design, it was assumed that the features of readily available commercial components would develop in the course of the design work, just as they did. By choosing a high speed it was possible to multiplex the data from some the chambers into the same fibres to reduce the number of links needed. Further reduction was achieved by employing zero suppression and data compression, and a total of only 660 optical links were needed. Another requirement, which conflicted somewhat with choosing the components a late as possible was that the design needed to be radiation tolerant to an ionizing dose of 100 Gy and to a have a moderate tolerance to Single Event Effects (SEEs). This required some radiation test campaigns, and eventually led to ASICs being chosen for some of the critical parts. The system was made to be as reconfigurable as possible. The reconfiguration needs to be done from a distance as the electronics is not accessible except for some short and rare service breaks once the accelerator starts running. Therefore reconfigurable logic is extensively used, and the firmware development for the FPGAs constituted a sizable part of the work. Some special techniques needed to be used there too, to achieve the required radiation tolerance. The system has been demonstrated to work in several laboratory and beam tests, and now we are waiting to see it in action when the LHC will start running in the autumn 2008.

Pienen kiinteistösijoitusyhtiön kasvustrategia

Tämän pro gradu-tutkielman tarkoituksena oli tutkia minkälaisia kasvupyrkimyksiä Suomessa toimivilla pienillä kiinteistösijoittajilla tai kiinteistösijoitusyhtiöillä on. Tutkimuksen pohjaksi esiteltiin yrityksen strategiateoriaa ja kasvun malleja pienyritysnäkökulmasta. Tutkimuksen tulokset voivat antaa yrittäjille mietteitä kasvamisen suunnitelmallisuudesta ja sen hyödyistä. Tutkimusosuus suoritettiin laadullisena tutkimuksena. Aineisto kerättiin haastattelemalla 16 pientä kiinteistösijoittajaa nettipohjaisen kyselyn avulla. Painopiste oli vapaissa vastauksissa ja tällä pyrittiin saamaan laajoja mielipiteitä. Kohdeyritykset valittiin sattumalta tutkijan lähipiiriin kuuluvien yrittäjien avulla. Maantieteellinen jakauma oli laaja, koko maan kattava. Kohdeyrityksistä haastateltiin yhtä henkilöä, joka oli tyypillisesti yrityksen omistaja. Haastatteluista saatua materiaalia analysoitiin strategisten näkemysten ja yrityksen kasvuteorioiden valossa. Tutkimuksessa todettiin, että pienyrittäjät suhtautuvat kiinteistösijoittamiseen lähinnä säästämismuotona eikä niinkään systemaattisena yrittämisenä. Useat vastaajat tekivät kiinteistösijoittamista osa-aikaisesti. Kasvua tavoittelee kyllä valtaosa yrityksistä, mutta sen eteen ei tehdä juuri mitään. Odotellaan vain sopivia kohteita ostettavaksi. Kasvamisen määrä riippuu hyvin pitkälti yrittäjän persoonasta. Jos yrittäjä on kunnianhimoinen toiminnan kasvattaja, niin se heijastuu myös hänen harjoittamaan kiinteistösijoittamiseen.