This master thesis investigates if there is an induction motor configuration that can be used with a flywheel energy storage system, that uses passve superconducting magnetic bearings (SMBs). The configurations should be able to be designed with induction motor building blocks that are commercially available. The method used to investigate this was simulations of different induction motor configurations in the finite element analysis software COMSOL. The simulations show that when larger air-gaps than that of a commercial IM unit are used it is possible to use SMBs in the IM. SMBs have the advantage of having zero resistance which makes it possible to store energy without resistance losses. However it was found that by using and IM with SMBs the generated power would be lower than that of a commercial unit.

This thesis describes a novel device, the Virtual Air Gap Variable Reactor (VAG-VR), which is capable of producing a continuously variable reactance by locally saturating a small section of the reactor core via an embedded dc control winding. Variable Reactors have many applications in the power industry such as control of line power flow, voltage regulation, reactive line compensation and limiting inrush currents. A variable reactor is most commonly implemented as a thyristor controlled reactor (TCR) by switching in and out a constant reactance to achieve an averaged variable reactance. By using a virtual air gap, a continuously variable reactance is possible. The VAG-VR offers a better dynamic response, without introducing the harmonics created by the thyristor switching of a TCR. The VAG-VR gives low triplen harmonics and therefore allows control of reactive power in single phase or unbalanced three phase systems as would be required in the distribution system. An experimental prototype VAG-VR was developed to investigate three main performance measures: steady state performance, dynamic response and harmonic performance. Over the operating range of the VAG-VR inductance was varied from 100% to 9% of its original value. The dynamic response of the VAG-VR is approximately one tenth of a cycle. This compares favorably to a TCR which responds in approximately half a cycle. Harmonics are also shown to be significantly reduced in the VAG-VR compared to the TCR. A dynamic model of the VAG-VR, suitable for incorporation into power system simulations, was developed and validated. Parameters were determined both experimentally and through finite element method (FEM) simulations. Both experimental and simulation results indicate that the VAG-VR offers a technically viable alternative to the TCR.

This thesis describes a novel device, the Virtual Air Gap Variable Reactor (VAG-VR), which is capable of producing a continuously variable reactance by locally saturating a small section of the reactor core via an embedded dc control winding. Variable Reactors have many applications in the power industry such as control of line power flow, voltage regulation, reactive line compensation and limiting inrush currents. A variable reactor is most commonly implemented as a thyristor controlled reactor (TCR) by switching in and out a constant reactance to achieve an averaged variable reactance. By using a virtual air gap, a continuously variable reactance is possible. The VAG-VR offers a better dynamic response, without introducing the harmonics created by the thyristor switching of a TCR. The VAG-VR gives low triplen harmonics and therefore allows control of reactive power in single phase or unbalanced three phase systems as would be required in the distribution system. An experimental prototype VAG-VR was developed to investigate three main performance measures: steady state performance, dynamic response and harmonic performance. Over the operating range of the VAG-VR inductance was varied from 100% to 9% of its original value. The dynamic response of the VAG-VR is approximately one tenth of a cycle. This compares favorably to a TCR which responds in approximately half a cycle. Harmonics are also shown to be significantly reduced in the VAG-VR compared to the TCR. A dynamic model of the VAG-VR, suitable for incorporation into power system simulations, was developed and validated. Parameters were determined both experimentally and through finite element method (FEM) simulations. Both experimental and simulation results indicate that the VAG-VR offers a technically viable alternative to the TCR.

<p>The air gap method is a modification of the common way of building indoor walls and floors. The aim of the method is to make a construction, less fragile to water damage, with air gaps where moisture can be removed with a thermally driven air flow, caused by a heating cable. The thesis includes a number of experimental studies of this method.</p><p>Temperature and convective air flow in a vertical air gap was studied and it was noted how air flow increased with raised power of the heating cable. The air flow for one meter of wall varied between 50 m3/day (13 air changes per hour) and 140 m3/day (36 air changes per hour). The lower value was caused by a temperature difference in the range 0.2-0.3 oC. Without heating no air flow was found.</p><p>In studies of moisture and RH in wet “slab on ground” constructions, it was noted how the slab in the room with the air gap method dried to a much higher extent than the slab in the room built in an ordinary way. It was also noted that moisture was transported from the air gap in the floor and up through the air gap in the wall. In the room with the air gap construction, the RH values beneath the floor was at a lower level (and below 75 % RH) than the RH values beneath the floor of conventional construction. Mould does not grow below 75 % RH.</p><p>In the study of a flooded intermediate floor it was noted how the thermally driven convective air flow evidently speeded up drying of the construction. Mould growth was only noted in the case where the heating cables were turned off.</p> / <p>Spaltmetoden är en modifiering av det reguljära sättet av att bygga innerväggar och bjälklag. Syftet med metoden är att skapa en byggnadskonstruktion som är mindre skör med avseende på fuktskador. Detta görs med spalter där fukt kan avlägsnas genom ett termiskt drivet luftflöde som orsakas av en värmekabel. Denna avhandling innehåller ett antal experimentella studier på metoden. Spaltmetoden har studerats med avseende på 1. Samband mellan temperatur och luftflöde, 2. Uttorkning och RF nivåer i golvkonstruktioner samt 3. Översvämning av ett mellanbjälklag</p><p><strong>1. Samband mellan temperatur och luftflöde</strong></p><p>Temperatur och konvektivt luftflöde har studerats i en vertikal spalt och resultatet visar att luftflödet ökar med ökad effekt hos värmekabeln. Luftflödet i en vägg med en meters bredd varierade mellan 50 kubikmeter/dag (13 luftväxlingar per timme) och 140 kubikmeter/dag (36 luftväxlingar per timme). Det lägre flödet orsakades av en temperaturskillnad på 0,2-0,3 oC mellan luftspalt och rum. När värmekabeln var avstängd så registrerades inget luftflöde.</p><p><strong>2. Uttorkning och RF nivåer i golvkonstruktioner ovan betongplatta</strong></p><p>Detta experiment visade att fukt har transporterats från spalten i golvet genom spalten i väggen ut i rumsluften. I spaltkonstruktion var RF inuti golvkonstruktionen lägre (och understeg 75 % RF), jämfört med den konventionella konstruktionen, (mögel växer inte under 75 % RF). Det har också registrerats att betongplattan som hörde till spaltmetoden torkade ut snabbare än betongplattan som var inbyggd i ett gängse rum.</p><p><strong>3. Översvämning av ett mellanbjälklag</strong></p><p>I studien där ett mellanbjälklag blev översvämmat noterades att spaltmetoden förkortade torktiden från 21 dagar till 13 vid den fuktigaste mätpunkten. Mögelväxt noterades endast då värmekabeln hade varit frånslagen.</p><p> </p><p> </p>

Die Arbeit beschreibt die Entwicklung und Evaluierung einer Technologieplattform für die Herstellung von oberflächennahen Mikrostrukturen mit hohen Aspektverhältnissen. Grundlage dieser Technologieplattform stellt ein neuartiges Konzept zur mechanischen und elektrischen Kontaktierung beweglicher Elemente mittels spezieller Träger dar, deren typische Breite unterhalb eines Mikrometers liegt. Basierend hierauf werden drei unterschiedliche Prozessabläufe zur Herstellung der Mikrostrukturen, auch als Air gap Insulated Microstructures (AIM) bezeichnet, vorgestellt. Der Schwerpunkt dieser Arbeit liegt dabei auf der mehrschichtigen Trägervariante mit Isolationsebene und Leitungsebene. Verschiedene Schichtkombinationen, bestehend aus Siliziumnitrid, Siliziumdioxid und Aluminium, sind in ihrem mechanischen, thermischen und Langzeitverhalten charakterisiert und im Hinblick auf ihre Anwendbarkeit für die Träger bewertet. Für die Strukturierung der Siliziumelemente wird ein Verfahren basierend auf einem CF-Polymer als Passivierungsschicht beschrieben. Neben verschiedenen Ausfallmechanismen für die Passivierung werden gezielte Optimierungen der Abscheide- und Ätzprozesse erläutert sowie deren Resultate dargestellt. Für die vollständige Trennung von Substrat und seismischer Masse ist eine isotrope, vom Aspektverhältnis nahezu unabhängige Siliziumstrukturierung nötig. Entsprechende Betrachtungen und Untersuchungen hierzu, unter Verwendung der Reaktionsgase SF6 und O2, stellen den Abschluss der Untersuchungen zur Prozessentwicklung dar. Um die Leistungsfähigkeit der Technologieplattform zu demonstrieren, erfolgt die Herstellung verschiedener Sensoren und Aktoren. Die Charakterisierung dieser Elemente in ihrem mechanischen, thermischen und Langzeitverhalten stellt den Abschluss dieser Arbeit dar.

The air gap method is a modification of the common way of building indoor walls and floors. The aim of the method is to make a construction, less fragile to water damage, with air gaps where moisture can be removed with a thermally driven air flow, caused by a heating cable. The thesis includes a number of experimental studies of this method. Temperature and convective air flow in a vertical air gap was studied and it was noted how air flow increased with raised power of the heating cable. The air flow for one meter of wall varied between 50 m3/day (13 air changes per hour) and 140 m3/day (36 air changes per hour). The lower value was caused by a temperature difference in the range 0.2-0.3 oC. Without heating no air flow was found. In studies of moisture and RH in wet “slab on ground” constructions, it was noted how the slab in the room with the air gap method dried to a much higher extent than the slab in the room built in an ordinary way. It was also noted that moisture was transported from the air gap in the floor and up through the air gap in the wall. In the room with the air gap construction, the RH values beneath the floor was at a lower level (and below 75 % RH) than the RH values beneath the floor of conventional construction. Mould does not grow below 75 % RH. In the study of a flooded intermediate floor it was noted how the thermally driven convective air flow evidently speeded up drying of the construction. Mould growth was only noted in the case where the heating cables were turned off. / Spaltmetoden är en modifiering av det reguljära sättet av att bygga innerväggar och bjälklag. Syftet med metoden är att skapa en byggnadskonstruktion som är mindre skör med avseende på fuktskador. Detta görs med spalter där fukt kan avlägsnas genom ett termiskt drivet luftflöde som orsakas av en värmekabel. Denna avhandling innehåller ett antal experimentella studier på metoden. Spaltmetoden har studerats med avseende på 1. Samband mellan temperatur och luftflöde, 2. Uttorkning och RF nivåer i golvkonstruktioner samt 3. Översvämning av ett mellanbjälklag 1. Samband mellan temperatur och luftflöde Temperatur och konvektivt luftflöde har studerats i en vertikal spalt och resultatet visar att luftflödet ökar med ökad effekt hos värmekabeln. Luftflödet i en vägg med en meters bredd varierade mellan 50 kubikmeter/dag (13 luftväxlingar per timme) och 140 kubikmeter/dag (36 luftväxlingar per timme). Det lägre flödet orsakades av en temperaturskillnad på 0,2-0,3 oC mellan luftspalt och rum. När värmekabeln var avstängd så registrerades inget luftflöde. 2. Uttorkning och RF nivåer i golvkonstruktioner ovan betongplatta Detta experiment visade att fukt har transporterats från spalten i golvet genom spalten i väggen ut i rumsluften. I spaltkonstruktion var RF inuti golvkonstruktionen lägre (och understeg 75 % RF), jämfört med den konventionella konstruktionen, (mögel växer inte under 75 % RF). Det har också registrerats att betongplattan som hörde till spaltmetoden torkade ut snabbare än betongplattan som var inbyggd i ett gängse rum. 3. Översvämning av ett mellanbjälklag I studien där ett mellanbjälklag blev översvämmat noterades att spaltmetoden förkortade torktiden från 21 dagar till 13 vid den fuktigaste mätpunkten. Mögelväxt noterades endast då värmekabeln hade varit frånslagen. / QC 20101101

Increasing the power density of the DC-DC converters requires the size and weight of the magnetic components, such as inductors and transformers, to be reduced. In this thesis, the losses in nanocrystalline inductor cores are characterised and analysed, including the traditional core loss and the gap loss caused by the air gap fringing flux. The loss calculations will form a basis for the design and optimisation of high power inductors for DC-DC converters for EV applications. This thesis first characterises experimentally the core losses in four nanocrystalline cores over a range of operating conditions that are representative of those encontered in typical high power converter applications, including non-sinusoidal waveforms and DC bias conditions. The core losses are assessed by the measured B-H loops and are characterised as a function of DC flux density, showing that for a fixed AC induction level, the losses can vary by almost an order of magnitude as the DC bias increases and the duty ratio moves away from 0.5. The results provide a more complete picture of the core loss variations with both DC and AC magnetisations than is available in manufactures’ data sheets. An electromagnetic finite element (FE) model is used to examine the gap loss that occurs in finely laminated nanocrystalline cores under high frequency operation. The loss is significant in the design example, contributing to almost half of the total inductor loss, and the gap loss is highly concentrated in the region of the air gap. The dependence of the gap loss on key inductor design parameters and operating condtions is also explored. An empirical equation is derived to provide a design-oriented basis for estimating gap losses. Thermal finite element analysis is used to estimate the temperature rise and identify the hot spot in a nanocrystalline inductor encapsulated in an alumimium case. The temperature distribution in the core largely corresponds to the non-uniform distribution of the gap loss. The thermal FEA can also be used to evaluate different thermal management methods to optimise the design for a more compact component. The FE modelling of gap loss and the thermal predictions are validated experimentally on a foil-wound Finemet inductor, showing good agreement between the predictions and measurements under various operating conditions.

With the widespread use of doubly-fed induction generators (DFIG) in wind energy conversion systems, condition monitoring is being given importance. Non-intrusive techniques like motor current signature analysis (MCSA), which involves looking for specific frequency components in the current spectrum, are preferred over analysis of magnetic field, temperature, vibrations or acoustic noise which require additional sensors. The major difficulty in MCSA is isolation of the fault, as multiple faults produce similar signatures. Moreover, closed-loop control makes diagnostics more complicated due to inherent compensation by the controller. This thesis presents a method to diagnose static and dynamic air gap eccentricities in doubly-fed induction generators operated for closed-loop stator power control by using a modified control technique to enable detection and isolation of this fault from electrical unbalances in the stator and rotor and load torque oscillations that produce similar effects. The effectiveness of the proposed control is verified using simulations and preliminary experiments performed on a healthy machine.

Low-loss off-chip interconnects are required for energy-efficient communication in dense microprocessors. To meet these needs, air cavity parallel plate and microstrip lines with copper conductors were fabricated on an FR-4 epoxy-fiberglass substrate using conventional microelectronics manufacturing techniques. Copper transmission lines were separated by a composite dielectric of air and Avatrel 2000P and by a dielectric layer of air only. The composite dielectric lines were characterized to 10 GHz while the all air dielectric lines were characterized to 40 GHz. The transmission line structures showed loss as low 1.5 dB/cm at 40 GHz with an effective dielectric constant below 1.4. These novel structures show low loss in the dielectric due to the reduced relative permittivity and loss tangent introduced by the air cavity. Transmission line structures with a composite dielectric were built by coating the sacrificial polymer poly(propylene carbonate) (PPC) over a copper signal line, encapsulating with an overcoat polymer, electroplating a ground line, and decomposing PPC to form an air cavity. The signal and ground wires were separated by a layer of 15 µm of air and 20 µm of Avatrel 2000P. Air cavity formation reduced dielectric constant more than 30 percent and loss of less than 0.5 dB/cm was measured at 10 GHz. Residue from PPC decomposition was observed in the cavity of composite dielectric structures and the decomposition characteristics of PPC were evaluated to characterize the residue and understand its formation. Analysis of PPC decomposition based on molecular weight, molecular backbone structure, photoacid concentration and vapor pressure, casting solvent, and decomposition environment was performed using thermogravimetric analysis and extracting kinetic parameters. Novel interaction of copper and PPC was observed and characterized for the self-patterning of PPC on copper. Copper is dissolved from the surface during PPC spincoating and interacts with the polymer chains to improve stability. The improved thermal stability allows selective patterning of PPC on copper. Decomposition characteristics, residual metals analysis, and diffusion profile were analyzed. The unique interaction could simplify air-gap processing for transmission lines. Inorganic-organic hybrid polymers were characterized for use as overcoat materials. Curing characteristics of the monomers and mechanical properties of the polymer films were analyzed and compared with commercially available overcoat materials. The modulus and hardness of these polymers was too low for use as an air-gap overcoat, but may be valuable as a barrier layer for some applications. The knowledge gained from building transmission line structures with a composite dielectric, analyzing PPC decomposition, interaction with copper, and comparison of hybrid polymers with commercial overcoats was used to build air-gap structures with improved electrical design. The ground metal was separated from the signal only by air. The signal wire was supported from above using 60 µm of Avatrel 8000P as an overcoat. Structures showed loss of less than 1.5 dB/cm at 40 GHz, the lowest reported value for a fully encapsulated transmission line structure.

Ο εξοπλισμός και οι αγωγοί που μεταφέρουν την υψηλή τάση ακολουθούν συγκεκριμένες τιμές ασφάλειας και ελέγχου. Με τον όρο υπερτάσεις εννοούμε τις τάσεις που εμφανίζονται στα ηλεκτρικά δίκτυα και που συνήθως έχουν εύρος μεγαλύτερο από εκείνο της κανονικής τάσης λειτουργίας. Οι υπερτάσεις έχουν κατά κανόνα ανώμαλη μορφή και είναι ικανές να προκαλέσουν διηλεκτρικές καταπονήσεις μεγάλου μεγέθους στις μονώσεις ενός συστήματος. Κατά τον σχεδιασμό της μόνωσης ενός συστήματος υπάρχουν δύο εξαιρετικά σημαντικές παράμετροι που πρέπει να ληφθούν υπ’όψην από τους κατασκευαστές: 1) Ο καθορισμός της μορφής των τάσεων που καταπονούν την μόνωση 2) Ο καθορισμός της αντοχής της μόνωσης όταν υφίσταται καταπόνηση από συγκεκριμένες μορφές τάσεων. Σκοπός της παρούσας εργασίας είναι η ανάλυση της καταπόνησης που υφίσταται διάκενο ακίδα-πλάκα συνολικού μήκους 6cm στο οποίο παρεμβλήθηκε μετακινούμενο διάφραγμα. Τα συμπεράσματα που εξήχθησαν αφορούν την μελέτη της τάσης διάσπασης και τον τρόπο με τον οποίο αυτή μεταβάλλεται σε σχέση με την γεωμετρία του διακένου αλλά και τις ατμοσφαιρικές συνθηκες. Τα συμπεράσματα που προκύπτουν από την ανάλυση της καταπόνησης που υφίσταται διάκενο ακίδας-πλάκας είναι ότι καθώς απομακρύνεται το διάφραγμα από την ακίδα η τάση διάσπασης μειώνεται. Αξίζει επίσης να σημειωθεί ότι όσο πλησιάζει το διάφραγμα την ακίδα μειώνεται η τυχαιότητα του φαινομένου της διάσπασης πράγμα το οποιό σημαίνει πως ο σχεδιασμός ενός συστήματος μόνωσης δύναται να γίνει πιο ακριβής. Τέλος παρατηρείται ότι ανάμεσα σε σετ μετρήσεων με ίδια απόσταση διαφράγματος από την ακίδα υπάρχει μια απόκλιση στις τιμές της U50%. Αυτή η απόκλιση οφείλεται σε διάφορους παράγοντες. Ένας εξ’αυτών είναι η μικρή μεταβολή των ατμοσφαιρικών συνθηκών κατά την χρονική απόσταση που παρεμβλήθηκε ανάμεσα στα σετ μετρήσεων. Έναν δεύτερο παράγοντα αποτελούν οι πιθανές υπερπηδήσεις που συνέβησαν κατά την διάρκεια των επιβολών τάσης στο διάκενο. / The equipment and conductors that "carry" high voltage are taking specific values of security and control. Using the term, hyper-voltage, the researchers mean those voltages that appear in electricity networks and they usually have a width value greater than the normal operating voltage. Most of the times, hyper-voltages are typically have irregular form and they are capable of causing large dielectric stresses in the insulation of a system. When designing an insulation system there are two very important parameters that have to be taken under consideration by the manufacturers: 1) The determination of a voltage form that stresses the insulation equipment 2) The determination of the insulation resistance when there is strain from specific voltage forms. The purpose of this paper is to analyze the voltage stress that is happening in a 6cm gap of pin-plate which was inserted by removable diaphragm. The conclusions drawn are concerning the study of breakdown voltage and how it changes with respect to the geometry of the gap and the atmospheric conditions. One conclusion that arises from the stress analysis of the pin-plate gap is that when the diaphragm is moving away from the pin the breakdown voltage is decreasing. It is also worth noting that as the diaphragm is moving towards the pin, the breakdown phenomenon is becoming less random. This means that the design of an insulation system can be made more accurate. Another conclusion is related to the discrepancy in the values of U50% between different sets of measurements. The distance between the diaphragm and the spike is influencing the above observation. This discrepancy is due to several factors. The first factor is related to the small change of weather conditions during the different sets of measurements. The second factor is related to the possible jumps that occurred during the voltage imposition in the gap.