Remediation strategies of shaft and common mode voltages in adjustable speed drive systems

AC motors are largely used in a wide range of modern systems, from household appliances to automated industry applications such as: ventilations systems, fans, pumps, conveyors and machine tool drives. Inverters are widely used in industrial and commercial applications due to the growing need for speed control in ASD systems. Fast switching transients and the common mode voltage, in interaction with parasitic capacitive couplings, may cause many unwanted problems in the ASD applications. These include shaft voltage and leakage currents. One of the inherent characteristics of Pulse Width Modulation (PWM) techniques is the generation of the common mode voltage, which is defined as the voltage between the electrical neutral of the inverter output and the ground. Shaft voltage can cause bearing currents when it exceeds the amount of breakdown voltage level of the thin lubricant film between the inner and outer rings of the bearing. This phenomenon is the main reason for early bearing failures. A rapid development in power switches technology has lead to a drastic decrement of switching rise and fall times. Because there is considerable capacitance between the stator windings and the frame, there can be a significant capacitive current (ground current escaping to earth through stray capacitors inside a motor) if the common mode voltage has high frequency components. This current leads to noises and Electromagnetic Interferences (EMI) issues in motor drive systems. These problems have been dealt with using a variety of methods which have been reported in the literature. However, cost and maintenance issues have prevented these methods from being widely accepted. Extra cost or rating of the inverter switches is usually the price to pay for such approaches. Thus, the determination of cost-effective techniques for shaft and common mode voltage reduction in ASD systems, with the focus on the first step of the design process, is the targeted scope of this thesis. An introduction to this research – including a description of the research problem, the literature review and an account of the research progress linking the research papers – is presented in Chapter 1. Electrical power generation from renewable energy sources, such as wind energy systems, has become a crucial issue because of environmental problems and a predicted future shortage of traditional energy sources. Thus, Chapter 2 focuses on the shaft voltage analysis of stator-fed induction generators (IG) and Doubly Fed Induction Generators DFIGs in wind turbine applications. This shaft voltage analysis includes: topologies, high frequency modelling, calculation and mitigation techniques. A back-to-back AC-DC-AC converter is investigated in terms of shaft voltage generation in a DFIG. Different topologies of LC filter placement are analysed in an effort to eliminate the shaft voltage. Different capacitive couplings exist in the motor/generator structure and any change in design parameters affects the capacitive couplings. Thus, an appropriate design for AC motors should lead to the smallest possible shaft voltage. Calculation of the shaft voltage based on different capacitive couplings, and an investigation of the effects of different design parameters are discussed in Chapter 3. This is achieved through 2-D and 3-D finite element simulation and experimental analysis. End-winding parameters of the motor are also effective factors in the calculation of the shaft voltage and have not been taken into account in previous reported studies. Calculation of the end-winding capacitances is rather complex because of the diversity of end winding shapes and the complexity of their geometry. A comprehensive analysis of these capacitances has been carried out with 3-D finite element simulations and experimental studies to determine their effective design parameters. These are documented in Chapter 4. Results of this analysis show that, by choosing appropriate design parameters, it is possible to decrease the shaft voltage and resultant bearing current in the primary stage of generator/motor design without using any additional active and passive filter-based techniques. The common mode voltage is defined by a switching pattern and, by using the appropriate pattern; the common mode voltage level can be controlled. Therefore, any PWM pattern which eliminates or minimizes the common mode voltage will be an effective shaft voltage reduction technique. Thus, common mode voltage reduction of a three-phase AC motor supplied with a single-phase diode rectifier is the focus of Chapter 5. The proposed strategy is mainly based on proper utilization of the zero vectors. Multilevel inverters are also used in ASD systems which have more voltage levels and switching states, and can provide more possibilities to reduce common mode voltage. A description of common mode voltage of multilevel inverters is investigated in Chapter 6. Chapter 7 investigates the elimination techniques of the shaft voltage in a DFIG based on the methods presented in the literature by the use of simulation results. However, it could be shown that every solution to reduce the shaft voltage in DFIG systems has its own characteristics, and these have to be taken into account in determining the most effective strategy. Calculation of the capacitive coupling and electric fields between the outer and inner races and the balls at different motor speeds in symmetrical and asymmetrical shaft and balls positions is discussed in Chapter 8. The analysis is carried out using finite element simulations to determine the conditions which will increase the probability of high rates of bearing failure due to current discharges through the balls and races.

Using Fiber Bragg Grating (FBG) sensors to measure vertical displacements of bridges : a preliminary study

In many bridges, vertical displacements are the most relevant parameter for monitoring in the both short and long term. However, it is difficult to measure vertical displacements of bridges and yet they are among the most important indicators of structural behaviour. Therefore, it prompts a need to develop a simple, inexpensive and yet more practical method to measure vertical displacements of bridges. With the development of fiber-optics technologies, fiber Bragg grating (FBG) sensors have been widely used in structural health monitoring. The advantages of these sensors over the conventional sensors include multiplexing capabilities, high sample rate, small size and electro magnetic interference (EMI) immunity. In this paper, methods of vertical displacement measurements of bridges are first reviewed. Then, FBG technology is briefly introduced including principle, sensing system, characteristics and different types of FBG sensors. Finally, the methodology of vertical displacement measurements using FBG sensors is presented and a trial test is described. It is concluded that using FBG sensors is feasible to measure vertical displacements of bridges. This method can be used to understand global behaviour of bridge‘s span and can further develop for structural health monitoring techniques such as damage detection.

Minimising capacitive couplings and distributing copper losses in planar magnetic elements

Planar magnetic elements are becoming a replacement for their conventional rivals. Among the reasons supporting their application, is their smaller size. Taking less bulk in the electronic package is a critical advantage from the manufacturing point of view. The planar structure consists of the PCB copper tracks to generate the desired windings .The windings on each PCB layer could be connected in various ways to other winding layers to produce a series or parallel connection. These windings could be applied coreless or with a core depending on the application in Switched Mode Power Supplies (SMPS). Planar shapes of the tracks increase the effective conduction area in the windings, brings about more inductance compared to the conventional windings with the similar copper loss case. The problem arising from the planar structure of magnetic inductors is the leakage current between the layers generated by a pulse width modulated voltage across the inductor. This current value relies on the capacitive coupling between the layers, which in its turn depends on the physical parameters of the planar scheme. In order to reduce this electrical power dissipation due to the leakage current and Electromagnetic Interference (EMI), reconsideration in the planar structure might be effective. The aim of this research is to address problem of these capacitive coupling in planar layers and to find out a better structure for the planar inductance which offers less total capacitive coupling and thus less thermal dissipation from the leakage currents. Through Finite Element methods (FEM) several simulations have been carried out for various planar structures. The labs prototypes of these structures are built with the similar specification of the simulation cases. The capacitive couplings of the samples are determined with Spectrum Analyser whereby the test analysis verified the simulation results.

Fiber Bragg Grating sensors for railway systems

Fiber Bragg grating (FBG) sensor technology has been attracting substantial industrial interests for the last decade. FBG sensors have seen increasing acceptance and widespread use for structural sensing and health monitoring applications in composites, civil engineering, aerospace, marine, oil & gas, and smart structures. One transportation system that has been benefitted tremendously from this technology is railways, where it is of the utmost importance to understand the structural and operating conditions of rails as well as that of freight and passenger service cars to ensure safe and reliable operation. Fiberoptic sensors, mostly in the form of FBGs, offer various important characteristics, such as EMI/RFI immunity, multiplexing capability, and very long-range interrogation (up to 230 km between FBGs and measurement unit), over the conventional electrical sensors for the distinctive operational conditions in railways. FBG sensors are unique from other types of fiber-optic sensors as the measured information is wavelength-encoded, which provides self-referencing and renders their signals less susceptible to intensity fluctuations. In addition, FBGs are reflective sensors that can be interrogated from either end, providing redundancy to FBG sensing networks. These two unique features are particularly important for the railway industry where safe and reliable operations are the major concerns. Furthermore, FBGs are very versatile and transducers based on FBGs can be designed to measure a wide range of parameters such as acceleration and inclination. Consequently, a single interrogator can deal with a large number of FBG sensors to measure a multitude of parameters at different locations that spans over a large area.

A threshold analysis of dengue transmission in terms of weather variables and imported dengue cases in Australia

Dengue virus (DENV) transmission in Australia is driven by weather factors and imported dengue fever (DF) cases. However, uncertainty remains regarding the threshold effects of high-order interactions among weather factors and imported DF cases and the impact of these factors on autochthonous DF. A time-series regression tree model was used to assess the threshold effects of natural temporal variations of weekly weather factors and weekly imported DF cases in relation to incidence of weekly autochthonous DF from 1 January 2000 to 31 December 2009 in Townsville and Cairns, Australia. In Cairns, mean weekly autochthonous DF incidence increased 16.3-fold when the 3-week lagged moving average maximum temperature was <32 °C, the 4-week lagged moving average minimum temperature was ≥24 °C and the sum of imported DF cases in the previous 2 weeks was >0. When the 3-week lagged moving average maximum temperature was ≥32 °C and the other two conditions mentioned above remained the same, mean weekly autochthonous DF incidence only increased 4.6-fold. In Townsville, the mean weekly incidence of autochthonous DF increased 10-fold when 3-week lagged moving average rainfall was ≥27 mm, but it only increased 1.8-fold when rainfall was <27 mm during January to June. Thus, we found different responses of autochthonous DF incidence to weather factors and imported DF cases in Townsville and Cairns. Imported DF cases may also trigger and enhance local outbreaks under favorable climate conditions.

Twelve : the best Of IMP's 100 Songs Project 2011

12 Original recordings curated by leading national industry figures. It’s a 12 track album full of remixed, rerecorded and rejigged tracks from the project that were shortlisted by our friends at MGM Distribution, Music Sales, and EMI Music Australia. The TWELVE album is already receiving critical acclaim from Australia's music industry.

Indie 100 2013

The Independent Music Project is centred around the development and creation of new music, and includes research into copyright, business models of the future, new technologies, and new audiences. The music industry is undergoing the most radical changes it has faced in almost a century. New digital technologies have made the production, distribution, and promotion of recorded music accessible to anyone with a personal computer. People can now make high-quality digital copies of music and distribute them globally within minutes. Even bastions of the established industries, such as EMI and Columbia, are struggling to make sense of the new industry terrain. The whole employment picture has changed just as radically for people who wish to make a living from music. In Australia, many of the avenues that provided employment for musicians have either disappeared or dramatically shrunk. The advertising industry no longer provides the level of employment it used to prior to the Federal deregulation of the industry in 1992. In many places, new legislative pressures on inner-city and suburban venues have diminished the number of performance spaces that musicians can work in. Just as quickly, new sectors have opened to professional musicians: computer games, ringtones, sound-enabled toys and web advertising all present new opportunities to the enterprising musician. The opportunity to distribute music internationally without being signed to a major label is very attractive to many aspiring and established professionals. No doubt the music industry will face many more challenges as technologies continue to change, as global communication gets easier and faster, and as the challenges to copyright proliferate and change. These challenges cannot be successfully met on a single front. They require research and expertise from all sectors being affected, and this is why the independent music project (IMP) exists.

Indie 100 2014

The Independent Music Project is centred around the development and creation of new music, and includes research into copyright, business models of the future, new technologies, and new audiences. The music industry is undergoing the most radical changes it has faced in almost a century. New digital technologies have made the production, distribution, and promotion of recorded music accessible to anyone with a personal computer. People can now make high-quality digital copies of music and distribute them globally within minutes. Even bastions of the established industries, such as EMI and Columbia, are struggling to make sense of the new industry terrain. The whole employment picture has changed just as radically for people who wish to make a living from music. In Australia, many of the avenues that provided employment for musicians have either disappeared or dramatically shrunk. The advertising industry no longer provides the level of employment it used to prior to the Federal deregulation of the industry in 1992. In many places, new legislative pressures on inner-city and suburban venues have diminished the number of performance spaces that musicians can work in. Just as quickly, new sectors have opened to professional musicians: computer games, ringtones, sound-enabled toys and web advertising all present new opportunities to the enterprising musician. The opportunity to distribute music internationally without being signed to a major label is very attractive to many aspiring and established professionals. No doubt the music industry will face many more challenges as technologies continue to change, as global communication gets easier and faster, and as the challenges to copyright proliferate and change. These challenges cannot be successfully met on a single front. They require research and expertise from all sectors being affected, and this is why the independent music project (IMP) exists.

100 Songs Project 2012

The Independent Music Project is centred around the development and creation of new music, and includes research into copyright, business models of the future, new technologies, and new audiences. The music industry is undergoing the most radical changes it has faced in almost a century. New digital technologies have made the production, distribution, and promotion of recorded music accessible to anyone with a personal computer. People can now make high-quality digital copies of music and distribute them globally within minutes. Even bastions of the established industries, such as EMI and Columbia, are struggling to make sense of the new industry terrain. The whole employment picture has changed just as radically for people who wish to make a living from music. In Australia, many of the avenues that provided employment for musicians have either disappeared or dramatically shrunk. The advertising industry no longer provides the level of employment it used to prior to the Federal deregulation of the industry in 1992. In many places, new legislative pressures on inner-city and suburban venues have diminished the number of performance spaces that musicians can work in. Just as quickly, new sectors have opened to professional musicians: computer games, ringtones, sound-enabled toys and web advertising all present new opportunities to the enterprising musician. The opportunity to distribute music internationally without being signed to a major label is very attractive to many aspiring and established professionals. No doubt the music industry will face many more challenges as technologies continue to change, as global communication gets easier and faster, and as the challenges to copyright proliferate and change. These challenges cannot be successfully met on a single front. They require research and expertise from all sectors being affected, and this is why the independent music project (IMP) exists.

100 Songs Project 2011

The Independent Music Project is centred around the development and creation of new music, and includes research into copyright, business models of the future, new technologies, and new audiences. The music industry is undergoing the most radical changes it has faced in almost a century. New digital technologies have made the production, distribution, and promotion of recorded music accessible to anyone with a personal computer. People can now make high-quality digital copies of music and distribute them globally within minutes. Even bastions of the established industries, such as EMI and Columbia, are struggling to make sense of the new industry terrain. The whole employment picture has changed just as radically for people who wish to make a living from music. In Australia, many of the avenues that provided employment for musicians have either disappeared or dramatically shrunk. The advertising industry no longer provides the level of employment it used to prior to the Federal deregulation of the industry in 1992. In many places, new legislative pressures on inner-city and suburban venues have diminished the number of performance spaces that musicians can work in. Just as quickly, new sectors have opened to professional musicians: computer games, ringtones, sound-enabled toys and web advertising all present new opportunities to the enterprising musician. The opportunity to distribute music internationally without being signed to a major label is very attractive to many aspiring and established professionals. No doubt the music industry will face many more challenges as technologies continue to change, as global communication gets easier and faster, and as the challenges to copyright proliferate and change. These challenges cannot be successfully met on a single front. They require research and expertise from all sectors being affected, and this is why the independent music project (IMP) exists.

Suomi kasvitieteen kieleksi : Elias Lönnrot termistön kehittäjänä

The development of botanical Finnish: Elias Lönnrot as the creator of new terminology In the 19th century the Finnish language was intentionally developed to meet the demands of civilised society and Finnish-language science. The development of the language involved several people from different fields of science. This study examines this enormous project in the field of botany. By which methods were scientific terms formed, and for which reasons were those terms used? Why has a certain word been chosen to represent a particular concept? The material of this study is the terminology of plant morphology in Finnish that Elias Lönnrot developed in the middle of the 19th century. The terms of plant morphology denote and describe the parts of the plant and the relationships between those parts. For instance, the terms emi pistill , hede stamen , terälehti petal and verholehti sepal , which are nowadays familiar in the general language, were used for the first time in Lönnrot s texts. The study integrates the methods of lexicology and terminology. In lexicology, the word and its various meanings serve as the focus, whereas the theory of terminology focuses on the concept and concept systems. A new, consciously developed terminology can be understood through the old, familiar vocabulary and structures as well as through the new, logical term system. Lönnrot s botanical terminology can be divided into three groups depending on their origin: 1) 19% of all terms have been accepted from the existing vocabulary and used in their original meanings, 2) 11% of all terms have been chosen from the existing vocabulary and used in the new, specific botanical meanings, and 3) 70% of all terms have been created on the basis of the existing vocabulary and used in the new, specific botanical meanings. Therefore, the study reveals that domestic materials primarily morphosemantic neologisms form the Finnish terminology of plant morphology. Characteristic of Lönnrot s botanical terms is the utilisation of the vocabulary of various Finnish dialects and particular repeating elements. Repeating elements include, for example, the prefixes that come from botanical Latin or Swedish as well as the particular Finnish derivation types. Such structures form term systems that reflect scientific concept systems. Two thirds of the created new words are formed loosely or precisely according to either Latin or Swedish terms; one third is formed completely differently from its equivalents in the foreign languages. Approximately half of the chosen terms are formed differently from the Latin and Swedish terms. It is worth noting that many loan translations use rare vocabulary from Finnish dialects as equivalents to foreign parts of terms. Lönnrot aimed to inspire scientific terminology with Finland s own language, thus making scientific text accessible to the Finnish agricultural population.

Grid interfacing of a photovoltaic system using a chain cell converter

With the rapid development of photovoltaic system installations and increased number of grid connected power systems, it has become imperative to develop an efficient grid interfacing instrumentation suitable for photovoltaic systems ensuring maximum power transfer. The losses in the power converter play an important role in the overall efficiency of a PV system. Chain cell converter is considered to be efficient as compared to PWM converters due to lower switching losses, modularized circuit layout, reduced voltage rating of the converter switches, reduced EMI. The structure of separate dc sources in chain cell converter is well suited for photovoltaic systems as there will b several separate PV modules in the PV array which can act as an individual dc source. In this work, a single phase multilevel chain cell converter is used to interface the photovoltaic array to a single phase grid at a frequency of 50Hz. Control algorithms are developed for efficient interfacing of the PV system with grid and isolating the PV system from grid under faulty conditions. Digital signal processor TMS320F 2812 is used to implement the control algorithms developed and for the generation of other control signals.

Health Monitoring Of Composite Structures Based On Acoustic Wave Sensing Using Fiber Optic Sensors

Structural Health Monitoring has gained wide acceptance in the recent past as a means to monitor a structure and provide an early warning of an unsafe condition using real-time data. Utilization of structurally integrated, distributed sensors to monitor the health of a structure through accurate interpretation of sensor signals and real-time data processing can greatly reduce the inspection burden. The rapid improvement of the Fiber Optic Sensor technology for strain, vibration, ultrasonic and acoustic emission measurements in recent times makes it feasible alternative to the traditional strain gauges, PVDF and conventional Piezoelectric sensors used for Non Destructive Evaluation (NDE) and Structural Health Monitoring (SHM). Optical fiber-based sensors offer advantages over conventional strain gauges, and PZT devices in terms of size, ease of embedment, immunity from electromagnetic interference (EMI) and potential for multiplexing a number of sensors. The objective of this paper is to demonstrate the acoustic wave sensing using Extrinsic Fabry-Perot Interferometric (EFPI) sensor on a GFRP composite laminates. For this purpose experiments have been carried out initially for strain measurement with Fiber Optic Sensors on GFRP laminates with intentionally introduced holes of different sizes as defects. The results obtained from these experiments are presented in this paper. Numerical modeling has been carried out to obtain the relationship between the defect size and strain.

Structural Health Monitoring (SHM) Using Strain Gauges, PVDF Film and Fiber Bragg Grating (FBG) Sensors: A Comparative Study

The term Structural Health Monitoring has gained wide acceptance in the recent pastas a means to monitor a structure and provide an early warning of an unsafe conditionusing real-time data. Utilization of structurally integrated, distributed sensors tomonitor the health of a structure through accurate interpretation of sensor signals andreal-time data processing can greatly reduce the inspection burden. The rapidimprovement of the Fiber Bragg Grating sensor technology for strain, vibration andacoustic emission measurements in recent times make them a feasible alternatives tothe traditional strain gauges transducers and conventional Piezoelectric sensors usedfor Non Destructive Evaluation (NDE) and Structural Health Monitoring (SHM).Optical fiber-based sensors offers advantages over conventional strain gauges, PVDFfilm and PZT devices in terms of size, ease of embedment, immunity fromelectromagnetic interference(EMI) and potential for multiplexing a number ofsensors. The objective of this paper is to demonstrate the feasibility of Fiber BraggGrating sensor and compare its utility with the conventional strain gauges and PVDFfilm sensors. For this purpose experiments are being carried out in the laboratory on acomposite wing of a mini air vehicle (MAV). In this paper, the results obtained fromthese preliminary experiments are discussed.

Application of composition gradient solid electrolytes in sensors and thermodynamic measurements

New compos~tiong radient solid electrolytes are developed which have application in high temperature solid state galvanic sensors and provide a new tool for thermodynamic measurements. The electrolyte consists oi a solid solution between two ionic conductors with a common mobile ion and spatial variation in composition of otber coxup nents. Incorporation of the composite electrolyte in sensors permits the use oi dissimilar gas electrodes. It is demonsuated, both experimentall y and theoretically, that the composition gradient of the relativeiy immobile species does not give rise to a diffusion potential.The emi of a cell is determined by the activity of the mobile species at the two eiectrodes. The thermodynamic properties of solid solutions can be measured using the gradient solid electrolyte. The experimental stuay is based on model systems A?(COj)x(S04)l-x (A=Na,K),where S \.aria across the electrolyte. The functionally gradient solid electrolytes used for activity measurements consist of pure carbonate at one ena and the solid solution under stuav at the other. The identical vaiues of activity, obtained h m t hree different modes of operation of the ceil. indicate unit transport number for the ddi metal ion in the graciient electrolyte. Tlle activities in the solid solutions exhibit moderate positive deviations from Raoult 's law.