Radio Frequency Measurement Method for Detecting Bearing Currents in Induction Motors

Induction motors are widely used in industry, and they are generally considered very reliable. They often have a critical role in industrial processes, and their failure can lead to significant losses as a result of shutdown times. Typical failures of induction motors can be classified into stator, rotor, and bearing failures. One of the reasons for a bearing damage and eventually a bearing failure is bearing currents. Bearing currents in induction motors can be divided into two main categories; classical bearing currents and inverter-induced bearing currents. A bearing damage caused by bearing currents results, for instance, from electrical discharges that take place through the lubricant film between the raceways of the inner and the outer ring and the rolling elements of a bearing. This phenomenon can be considered similar to the one of electrical discharge machining, where material is removed by a series of rapidly recurring electrical arcing discharges between an electrode and a workpiece. This thesis concentrates on bearing currents with a special reference to bearing current detection in induction motors. A bearing current detection method based on radio frequency impulse reception and detection is studied. The thesis describes how a motor can work as a “spark gap” transmitter and discusses a discharge in a bearing as a source of radio frequency impulse. It is shown that a discharge, occurring due to bearing currents, can be detected at a distance of several meters from the motor. The issues of interference, detection, and location techniques are discussed. The applicability of the method is shown with a series of measurements with a specially constructed test motor and an unmodified frequency-converter-driven motor. The radio frequency method studied provides a nonintrusive method to detect harmful bearing currents in the drive system. If bearing current mitigation techniques are applied, their effectiveness can be immediately verified with the proposed method. The method also gives a tool to estimate the harmfulness of the bearing currents by making it possible to detect and locate individual discharges inside the bearings of electric motors.

Sudenmorsian : radio-ooppera 1940 [!]

Äänitetty: 1968, Yleisradio.

Dispersion of Hybrid Electromagnetic-Spin Waves in the Slotline

The presented thesis is devoted to investigation of wave processes in hybrid ferrite / ferroelectric structures. Spin wave devices based on ferrite films have such disadvantages, as huge size of the magnetic systems, low tuning velocity, considerable power inputs for parameters control that limits possible device applications. The considered layered structures allow to overcome the disadvantages mentioned and to promote the development of novel class of tunable microwave devices. The proposed theoretical analysis is intended to construct a model of hybrid electromagnetic-spin waves. Based on the theoretical analysis the experimental investigations were carried out. The experimental resonance characteristics of ferrite / ferroelectric resonator were obtained and their tunability by means of magnetic and electric field was demonstrated.

Vatikaanin radio 80 vuotta

Vatikaanin radion 80-vuotisnäyttely Vatikaanin museossa.

Spin-Dynamics in Cold Gases of 87Rb and Atomic Hydrogen. The spins they are a-changin’

In this thesis the dynamics of cold gaseous atoms is studied. Two different atomic species and two different experimental techniques have been used. In the first part of the thesis experiments with Bose-Einstein condensates of Rb-87 are presented. In these experiments the methods of laser cooling and magnetic trapping of atoms were utilized. An atom chip was used as the experimental technique for implementation of magnetic trapping. The atom chip is a small integrated instrument allowing accurate and detailed manipulation of the atoms. The experiments with Rb-87 probed the behaviour of a falling beam of atoms outcoupled from the Bose-Einstein condensate by electromagnetic field induced spin flips. In the experiments a correspondence between the phases of the outcoupling radio frequency field and the falling beam of atoms was found. In the second part of the thesis experiments of spin dynamics in cold atomic hydrogen gas are discussed. The experiments with atomic hydrogen are conducted in a cryostat using a dilution refrigerator as the cooling method. These experiments concentrated on explaining and quantifying modulations in the electron spin resonance spectra of doubly polarized atomic hydrogen. The modifications to the previous experimental setup are described and the observation of electron spin waves is presented. The observed spin wave modes were caused by the identical spin rotation effect. These modes have a strong dependence on the spatial profile of the polarizing magnetic field. We also demonstrated confinement of these modes in regions of strong magnetic field and manipulated their spatial distribution by changing the position of the field maximum.

Tunable lumped-element bandpass filters for Cognitive Radio application

In this thesis the design of bandpass filters tunable at 400 MHz – 800 MHz was under research. Microwave filters are vital components which provide frequency selectivity in wide variety of electronic systems operating at high frequencies. Due to the occurrence of multi-frequency bands communication and diverse applications of wireless devices, requirement of tunable filters exists. The one of potential implementation of frequency-agile filters is frontends and spectrum sensors in Cognitive Radio (CR). The principle of CR is to detect and operate at a particular available spectrum without interfering with the primary user’s signals. This new method allows improving the efficiency of utilizing allocated spectrum such as TV band (400 MHz – 800 MHz). The focus of this work is development of sufficiently compact, low cost tunable filters with quite narrow bandwidth using currently available lumped-element components and PCB board technology. Filter design, different topologies and methods of tuning of bandpass filters are considered in this work. As a result, three types of topologies of bandpass filter were simulated and realised. They use digitally tunable capacitors (DTCs) for adjusting central frequency at TV "white space" spectrum. Measurements revealed that schematics presented in this work have proper output response and filters are successfully tuned by DTCs.

KAVA:n radio- ja tv-arkisto : ohjelmavirtaa ja talletuksia tutkimuskäyttöön

Teemanumero 1/2012: Arkisto.

Kognitiivinen radio sotilaallisessa käyttöympäristössä

Tutkielmassa arvioidaan kognitiivisen radion sotilaalliseen ympäristöön tuomia mahdollisuuksia. Radion kognitiivisuutta käsitellään kongitiivisten ominaisuuksien, kuten adaptiivisuuden tai tilannetietoisuuden, kautta. Painopisteenä on kognitiivisten ominaisuuksien tuomien vaikutusten tarkastelu operatiivisessa viitekehyksessä. Operatiivisia vaikutuksia tutkitaan uhkalähtöisesti eli arvioimalla, miten tietty kognitiivinen ominaisuus vaikuttaa yleisimpiin tiedonsiirtoverkon uhkiin. Tutkimus on kirjallisuustutkimus, jota on täydennetty asiantuntijahaastatteluin sekä -arvioin. Operatiiviset vaikutukset on tiivistetty taulukoimalla eri kognitiivisten ominaisuuksien ja yleisimpien tiedonsiirtojärjestelmien uhkat. Kognitiiviselle radiolle on useita erilaisia määritelmiä. Tutkielman perusteella ITU-R:n määritelmää voidaan pitää kattavana. Kaikkia kriteerejä täyttävää kognitiivista radiota ei ole vielä olemassa, vaikka kognitiivisia ominaisuuksia radioissa on ollut pitkään. Kognitiivinen radio, tai jo pelkästään ohjelmistoradio kehittyneillä kognitiivisilla ominaisuuksilla, tuo huomattavia mahdollisuuksia parantaa langattoman tiedonsiirron toimintakykyä sotilaallisessa käyttöympäristössä. Kognitiiviset ominaisuudet vaikuttavat merkittävästi niin viestitaktiikkaan kuin uhkaankin. Tiedonsiirtojärjestelmien ylläpito ja rakentaminen vaativat aiempaa enemmän suunnittelua ja ammattitaitoa, mutta toisaalta loppukäyttäjän osaamistasovaatimuksia voidaan laskea sitä mukaan, kun lähestytään 0- konfiguraatiojärjestelmiä. Radioiden kognitiivisuuden myötä voidaan myös passiivisiin uhkiin, esimerkiksi elektroniseen tiedusteluun, varautua aiempaa tehokkaammin. Aktiivisiin uhkiin, kuten häirintään, kognitiiviset ominaisuudet vaikuttavat jopa toiminnan fundamentteja muuttavasti: perinteiset häirintätehtävät voivat vaihtua esimerkiksi tiedustelua tukeviksi tehtäviksi. Kognitiivisia ominaisuuksia voi olla myös häirintäjärjestelmissä, mikä toisaalta tasapainottaa mutta toisaalta vaikeuttaa häirinnän vaikutuksen ennakointia ja arviointia. Tiedonsiirtojärjestelmien ohjelmistopohjaisuus nostaa kyberuhkan merkitystä arvioitaessa eri uhkien kokonaismerkityksiä. Onnistunut kyberoperaatio voi tarkoittaa koko järjestelmän lamautumista tai vakavaa tietovuotoa. Merkittävimpänä esteenä kognitiivisen radion kehittymiselle on taajuusregulaation jäykkyys. Paine taajuushallinnan muutokselle nousee erityisesti siviilipuolen kehittyvien mobiililaitteiden datansiirtomäärien kasvaessa. Lainsäädäntö antaa viranomaisille suuret valtuudet säädellä spektrin käyttöä poikkeusoloissa. Tämä mahdollistaa sotilaallisten järjestelmien suunnittelun ja kehittämisen taajuusriippumattomasti ja toisaalta myös edellyttää sitä.

Electrical status epilepticus during sleep. Continuous spikes and waves during sleep

ABSTRACT Maria Peltola Electrical status epilepticus during sleep – Continuous spikes and waves during sleep Department of Clinical Neurophysiology, University of Turku Department of Clinical Neurophysiology and Department of Pediatric Neurology, Children’s Hospital, Helsinki University Central Hospital Annales Universitatis Turkuensis, Medica-Odontologica, Turku, Finland, 2014 Background: Electrical status epilepticus during sleep (ESES) is an EEG phenomenon of frequent spikes and waves occurring in slow sleep. ESES relates to cognitive deterioration in heterogeneous childhood epilepsies. Validated methods to quantitate ESES are missing. The clinical syndrome, called epileptic encephalopathy with continuous spikes and waves during sleep (CSWS) is pharmacoresistant in half of the patients. Limited data exists on surgical treatment of CSWS. Aims and methods: The effects of surgical treatment were studied by investigating electroclinical outcomes in 13 operated patients (nine callosotomies, four resections) with pharmacoresistant CSWS and cognitive decline. Secondly, an objective paradigm was searched for assessing ESES by the semiautomatic quantification of spike index (SI) and measuring spike strength from EEG. Results: Postoperatively, cognitive deterioration was stopped in 12 (92%) patients. Three out of four patients became seizure-free after resective surgery. Callosotomy resulted in greater than 90% reduction of atypical absences in six out of eight patients. The preoperative propagation of ESES from one hemisphere to the other was associated with a good response. Semiautomatic quantification of SI was a robust method when the maximal interspike interval of three seconds was used to determine the “continuous” discharge in ten EEGs. SI of the first hour of sleep appeared representative of the whole night SI. Furthermore, the spikes’ root mean square was found to be a stable measure of spike strength when spatially integrated over multiple electrodes during steady NREM sleep. Conclusions: Patients with pharmacoresistant CSWS, based on structural etiology, may benefit from resective surgery or corpus callosotomy regarding both seizure outcome and cognitive prognosis. The semiautomated SI quantification, with proper userdefined settings and the new spatially integrated measure of spike strength, are robust and promising tools for quantifying ESES. Keywords: Electrical status epilepticus during sleep, ESES, continuous spikes and waves during sleep, CSWS, epilepsy surgery, spike index, spike strength, RMS TIIVISTELMÄ Maria Peltola Unenaikainen sähköinen status epilepticus Kliininen neurofysiologia, Turun yliopisto Kliininen neurofysiologia ja lastenneurologia, Lasten ja nuorten sairaala, Helsingin yliopistollinen keskussairaala Annales Universitatis Turkuensis, Medica-Odontologica, Turku, Suomi, 2014 Tausta: Sähköinen status epilepticus unessa (ESES) on aivosähkökäyrä (EEG)-ilmiö, jossa hidasaaltounen aikana esiintyy tiheä piikkihidasaaltopurkaus. ESES:n kvantifioimiseen ei ole olemassa validoituja menetelmiä. ESES on liitetty kognitiivisen tason laskuun ja tällöin puhutaan CSWS (continuous spikes and waves during sleep) - oireyhtymästä. CSWS ei vastaa lääkehoitoon puolella potilaista ja sen epilepsiakirurgisesta hoidosta on olemassa vain vähän tietoa. Tavoitteet ja menetelmät: Selvitimme retrospektiivisesti epilepsiakirurgian vaikusta elektrokliinisiin löydöksiin 13:lla lääkeresistenttiä CSWS-oireyhtymää sairastavalla lapsella, joilla oli rakenteellinen aivojen poikkeavuus. Toinen tavoite oli löytää objektiivinen puoliautomaattinen tapa mitata purkauksen määrää ja piikkien voimakkuutta EEG:stä. Tulokset: Kognitiivisen tason jatkuva heikentyminen loppui 12 (92 %) potilaalla leikkauksen jälkeen. Kolme neljästä resektiopotilaasta tuli kohtauksettomaksi. Kallosotomian jälkeen kuudella kahdeksasta potilaasta päivittäiset kohtaukset vähenivät yli 90 %:lla. Purkauksen leviäminen leikkausta edeltävästi vain yhdestä hemisfääristä toiseen liittyi hyvään leikkaushoitovasteeseen. Piikki-indeksi, jossa käytetään jatkuvan purkauksen määritelmänä maksimissaan kolmea sekuntia piikkien välillä, osoittautui luotettavaksi menetelmäksi ESES:n kvantifioimiseen. Useammasta elektrodista integroitu piikkien neliöllinen keskiarvo oli piikin voimakkuuden vakaa mitta häiriintymättömässä NREM-unessa. Päätelmät: Lääkehoidolle vastaamatonta CSWS:ää sairastavat potilaat, joilla on rakenteellinen aivopoikkeavuus ja yhdensuuntainen purkauksen leviämismalli, näyttävät kohtausten vähenemisen lisäksi hyötyvän epilepsiakirurgiasta kognitiivisesti. Puoliautomaattinen piikki-indeksin kvantifiointi sopivilla käyttäjäasetuksilla ja uusi spatiaalisesti integroitu piikin voimakkuuden mittari ovat stabiileja ja lupaavia ESES:n kvantitatiivisia mittareita. Avainsanat: Unenaikainen sähköinen status epilepticus, ESES, CSWS, epilepsiakirurgia, piikki-indeksi, piikin voimakkuus, neliöllinen keskiarvo

The radio frequency identification technology in the supply chain management: a case of a big logistics company

Nowadays global business trends force the adoption of innovative ICTs into the supply chain management (SCM). Particularly, the RFID technology is on high demand among SCM professionals due to its business advantages such as improving of accuracy and veloc-ity of SCM processes which lead to decrease of operational costs. Nevertheless, a question of the RFID technology impact on the efficiency of warehouse processes in the SCM re-mains open. The goal of the present study is to experiment the possibility of improvement order picking velocity in a warehouse of a big logistics company with the use of the RFID technology. In order to achieve this goal the following objectives have been developed: 1) Defining the scope of the RFID technology applications in the SCM; 2) Justification of the RFID technology impact on the SCM processes; 3) Defining a place of the warehouse order picking process in the SCM; 4) Identification and systematization of existing meth-ods of order picking velocity improvement; 5) Choosing of the study object and gathering of the empirical data about number of orders, number of hours spent per each order line daily during 5 months; 6) Processing and analysis of the empirical data; 7) Conclusion about the impact of the RFID technology on the speed of order picking process. As a result of the research it has been found that the speed of the order picking processes has not been changed as time has gone after the RFID adoption. It has been concluded that in order to achieve a positive effect in the speed of order picking process with the use of the RFID technology it is necessary to simultaneously implement changes in logistics and organizational management in 3PL logistics companies. Practical recommendations have been forwarded to the management of the company for further investigation and procedure.

Radio-frequency-based measurement methods for bearing current analysis in induction motors

The most common reason for a low-voltage induction motor breakdown is a bearing failure. Along with the increasing popularity of modern frequency converters, bearing failures have become the most important motor fault type. Conditions in which bearing currents are likely to occur are generated as a side effect of fast du/dt switching transients. Once present, different types of bearing currents can accelerate the mechanical wear of bearings by causing deformation of metal parts in the bearing and degradation of the lubricating oil properties.The bearing current phenomena are well known, and several bearing current measurement and mitigation methods have been proposed. Nevertheless, in order to develop more feasible methods to measure and mitigate bearing currents, better knowledge of the phenomena is required. When mechanical wear is caused by bearing currents, the resulting aging impact has to be monitored and dealt with. Moreover, because of the stepwise aging mechanism, periodically executed condition monitoring measurements have been found ineffective. Thus, there is a need for feasible bearing current measurement methods that can be applied in parallel with the normal operation of series production drive systems. In order to reach the objectives of feasibility and applicability, nonintrusive measurement methods are preferred. In this doctoral dissertation, the characteristics and conditions of bearings that are related to the occurrence of different kinds of bearing currents are studied. Further, the study introduces some nonintrusive radio-frequency-signal-based approaches to detect and measure parameters that are associated with the accelerated bearing wear caused by bearing currents.

Spin-electromagnetic waves spectra in multiferroic heterostructures

This work devotes to the theoretical investigations of spin-electromagnetic waves (SEW) propagating in a thin-film multiferroic structures that were composed of a slot-line and structures with several ferrite films. In contrast to earlier works, the spin-electromagnetic waves in the investigated structures are originated from two different electrodynamics coupling. The first one is coupling of the electromagnetic wave localized mainly in the slot-line with the spin wave excited mostly in the ferrite film. The second one is coupling of two spin waves in the different ferrite films separated by a thin ferroelectric film. For theoretical analysis of SEWs propagation in such kind of structures theories of their eigen-wave spectra were developed. Spectra of SEW in the investigated structures were calculated and analyzed. The range of electric and magnetic tunability of dispersion characteristic were investigated. Spectra of SEW in the investigated multiferroic structures are used for investigation of transfer function of periodic structures.

De radio aeternitatis seu honestate e suo fonte scilicet jure naturae, emanante

Variantti B.

De radio aeternitatis seu honestate e suo fonte scilicet jure naturae, emanante

Variantti A.