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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Precision Amplifier for Applications in Electrical Metrology / Precisionsförstärkare för tillämpning inom elektrisk metrologi

Johanssson, Stefan January 2009 (has links)
This master's thesis addresses two main problems. The first is how to suppress a common mode voltage that appears for current shunts, and the second how to let a voltage divider work under an unloaded condition to prevent loading errors and thereby a decreased measurement accuracy. Both these problems occurs during calibration of power meters, and verification of current shunts and voltage dividers. To the first problem three alternative solutions are presented; prototype a proposed instrumentation amplifier circuit, evaluate the commercial available instrumentation amplifier Analog Devices AD8130 or let the voltage measuring device suppress the common mode voltage. It is up to the researchers at SP to choose a solution. To address the second problem, a prototype buffer amplifier is built and verified. Measurements of the buffer amplifier show that it performs very well. At 100 kHz, the amplitude error is less than 20 μV/V, the phase error is less than 20 μrad, and the input Rp is over 10 MΩ. This is performance in line with the required to make accurate measurements possible at 100 kHz and over that.
22

Investigation of Antennas for C2C communication

Waqas, Abdul January 2010 (has links)
The road traffic density is continuously increasing. By the intensive use of automobiles, it comes to considerable difficulties and unpredictable events. The frequency of traffic obstructions, traffic jams and accidents will also increase in future. A solution for this problem would be that the driver would be supplied information when he is on the road. The information should be including about road and traffic conditions and also information about other vehicles, which in the near vicinity. This kind of information sharing between vehicles is called C2C communication.Especially in Europe there are many projects which are working for different C2C communcation applications, like. Objective of this thesis is based on former works, which optimized the antenna positions for C2C communication by ray tracing simulation. The investigation of antennas for the C2C communication, two different approches are taken in to account, a narrow band, and broad band. Investigation of transparent material for broad band is also the part of this thesis.
23

RCC-Jordfelsskydd, mätmodul för övertonsanalys / RCC-Earth Fault Protection, module for harmonic analysis

Hollander, Johan January 2009 (has links)
The majority of all power cuts that affects individuals and communities are caused by earth faults on the power transmission lines at 10kV and 20kV level [1]. If these power cuts could be eliminated, less disturbances and interrupts would lead to large amounts of money savings. Swedish Neutral has developed such a protection system. When an earth fault occurs power is injected into the neutral point of the transformer. The RCC (Residual Current Compensation) protection calculates a compensation current exactly 180 degrees out of phase to the fault current. Doing this, the voltage at the fault location becomes very close to zero, without affecting the power transmission. The protection system can only compensate automatically for the fundamental frequency (50Hz), and manually for the 3rd, 5th, 7th and 9th harmonics. In most cases, when the harmonics are very small it is not necessary to compensate for them. There are though cases when compensation for the harmonics is necessary. This thesis focuses on finding the best method to extract the content of a sampled signal regarding both simplicity and speed. Both amplitude and phase of each harmonic must be calculated. Is the proposed method suitable for the current computer system and how can it easily be implemented. Because the fundamental frequency is known and the harmonics are all multiples of the fundamental frequency it makes the task less complex. It is not necessary to use the FFT algorithm. The DFT can be calculated using correlation. Both phase and amplitude can be calculated very precisely with few samples and not so many computer operations.
24

PLC-Baserat Maskinlarm ombord Ms Calmare Nyckel

Andersson, Robert, Huss, Karl, Lagerberg, Henrik January 2009 (has links)
Denna examensrapport beskriver arbetet med att utveckla ett nytt övervaknings och maskinalarmsystem till utbildningsfartyget M/S Calmare Nyckel. Systemet som konstruerades är styrdatorbaserat med grafiskt presentation av driftsvärden. Projektet drevs av tre sjöingenjörsstudenter på Sjöfartshögskolan i Kalmar. / This graduate report describes the work relating to the development of a brand new monitoring and machinery alarm system onboard the training vessel M/S Calmare Nyckel. The system developed, is based on PLC automation technology, and allows graphical presentation of system data. The project was managed by three marine engineering students at the Kalmar Maritime Academy. / Klassning av alarmsystemet genomfördes 2009-05-18 av inspektör från transportstyrelsen. Systemet godkändes.
25

Nyinstallation av Larmsystem Till NOHAB-Diesel : Denna rapport innefattar förfarande från att konstruera och installera ett helt nytt larmsystem

Olsen, Erik, Larsson, Jens, Stjernström, Dennis January 2009 (has links)
Skolfartyget M/S Calmare Nyckel, som ägs och opereras av Sjöfartshögskolan i Kalmar används i utbildningssyfte av både blivande nautiker och maskinbefäl.   Driften av NOHAB-dieseln, som används som generator, har varit problemfylld med ständiga och oförklarliga stopp. Det larmsystem som installerades av Oskarshamnsvarvet var högst bristfälligt. Larmsystemet var personfarligt då det var byggd på 230volt, dessutom var larmpunkterna byggda i serie med endast en stoppindikering. Avsaknaden av elritningar över systemet gjorde att bristerna i larmsystemet inte kunde felsökas. Dessutom fanns ingen indikering i kontrollrummet utan endast lokalt vid NOHAB-dieseln.   Vi har gjort en nyinstallation av larmsystemet på mer personsäkra 24VDC, med samtliga larmpunkter parallella och med tillhörande indikering på panel, både lokalt vid NOHAB-dieseln samt i pulpeten för god översyn av systemet. Vidare har vi gjort kompletta ritningar över systemet för en god överblick och möjlighet att felsöka. I rapporten beskriver vi tillvägagångssättet för problemlösningar som uppstått under arbetet med att skapa ett fungerande larmsystem. / School ship M/S Calmare Nyckel, owned and operated by the Maritime University of Kalmar is used for training by both prospective merchant marine officer as well as engineers. The operation of NOHAB-diesel, used as a generator, has been problematic with frequent and unexplained stop. The alarm system installed by the Oskarshamn Shipyard was highly dysfunctional. The alarm system was dangerous to personnel when it was built on 230volt, furthermore were the alarm points constructed in series with only a stop indication. The lack of electrical drawings of the system made it impossible to trouble shot the deficiencies in the alarm system. Moreover, there was no alarm indication in the control room but only locally at the NOHAB-diesel.   We have made a new installation of the alarm system with the higher personal safety 24VDC, with all the alarms parallel with the corresponding indication on the panel, both locally at the NOHAB-diesel and on the control table for good review of the system. Furthermore, we have made complete drawings of the system enabling a good overview and the ability to troubleshoot.In this report we describe the approach to the problem solutions that have emerged in the process of creating a functioning alarm system.
26

GPS/Optical Encoder Based Navigation Methods for dsPIC Microcontroled Mobile Vehicle

Dincay, Berkan January 2010 (has links)
Optical encoders are being widely suggested for precise mobile navigation. Combining such sensor information with Global Positioning System (GPS) is a practical solution for reducing the accumulated errors from encoders and moving the navigational base into global coordinates with high accuracy. This thesis presents integration methods of GPS and optical encoders for a mobile vehicle that is controlled by microcontroller. The system analyzed includes a commercial GPS receiver, dsPIC microcontroller and mobile vehicle with optical encoders. Extended kalman filtering (EKF), real time curve matching, GPS filtering methods are compared and contrasted which are used for integrating sensors data. Moreover, computer interface, encoder interface and motor control module of dsPIC microprocessor have been used and explained. Navigation quality on low speeds highly depends greatly upon the processing of GPS data. Integration of sensor data is simulated for both EKF and real time curve matching technique and different behaviors are observed. Both methods have significantly improved the accuracy of the navigation. However, EKF has more advantages on solving the localization problem where it is also dealing with the uncertainties of the systems.
27

Use SNA instead of VNA to characterize indoor channel : implementing and rms theory

Lai, Jingou, Liu, Che January 2010 (has links)
In this report we focus on the use of an economical way on how Scalar Network Analyzer (SNA) works instead of Vector Network Analyzer (VNA) to estimate the phase angle of signals in indoor channel. This is detailed in RMS delay theory and simulation section, experimental is designed in the according Experiment Design section, where we also state the required measurements known from the math part. In our work, data are recorded both from two different channel characteristics. Method of achieving amplitude is by using deconvolution theory. The condition of applying Hilbert transform are highlighted as impulse response h(t) in time domain should be causal.  The recorded data amplitude is computed by Hilbert Transform, and therefore validate the condition using Inverse Discrete Fourier Transform (IDFT) back to time domain to achieve h(t). Power delay profile P(t) is therefore presented afterwards. In paper calculations of rms delay τrms  of the channel which is the most important variable are also performed, the results calculated from different windowing truncation and the LOS and NLOS characteristics are compared in discussion and conclusion section, it also includes Opinions of window functions chosen for the phase estimation.
28

Network Coverage Optimization Strategy in Wireless Sensor Networks Based on Particle Swarm Optimization

Fan, Zihao, Zhao, Wei January 2011 (has links)
Wireless sensor network is an intelligent network system which has the self-monitoring functionality. It consists of many low-cost, low-power and small-sized sensor nodes that can communicate with each other to perform sensing and data processing. Acting as an important role in the system, network coverage usually has a huge effect on the system’s lifetime.In this thesis, particle swarm algorithm was used as a method to optimize the coverage in the coverage of wireless sensor network. A network coverage optimization strategy based on particle swarm optimization was proposed and MATLAB was used as a tool to apply the algorithm. The model used in this thesis is the probability sensing model and the coverage type is area coverage. Effectiveness of the algorithm is proved by simulation. The simulation of the algorithm suggests the optimal deployment can be determined if a certain parameter which in this thesis is the sensing range is given.
29

Investigation of alternative current measurements in high-voltage applications

Holmgren, Jens January 2007 (has links)
ABB:s MACH2 system uses a number of currents to ignite thyristors for AC/DC-trassfformation and they are measured for control and protection. The measurement methods used today has major drawbacks. Two alternative techniques are investigated, one based on the Hall-Effect (HED) and the other based on Anisotropic Magnetoreistanse (AMR), both techniques sensing the magnetic field produced by currents in a conductor. The HED hawe low sensitivity so some kind of flux concentrators is needed. This adds volume, costs and complexity to the device. The AMR technique is much more sensitive than the HED. Unfortunately AMR are also much more sensitive for high over currents that may damage the devise, and they are not as common on te market. By testing linearity, step response and frequency dependency for some components, my conclusion is that HED components with toroidal flux concentrators utilizing magnetic feedback (Closed Loop, CL) may be used in this particular application. A drawback with CL are that they, when measuring sharp edged step signals, suffer from overshoots at the output that might activate the over current protection.
30

RCC-Jordfelsskydd, mätmodul för övertonsanalys / RCC-Earth Fault Protection, module for harmonic analysis

Hollander, Johan January 2009 (has links)
<p>The majority of all power cuts that affects individuals and communities are caused by earth faults on the power transmission lines at 10kV and 20kV level [1]. If these power cuts could be eliminated, less disturbances and interrupts would lead to large amounts of money savings.</p><p>Swedish Neutral has developed such a protection system. When an earth fault occurs power is injected into the neutral point of the transformer. The RCC (Residual Current Compensation) protection calculates a compensation current exactly 180 degrees out of phase to the fault current. Doing this, the voltage at the fault location becomes very close to zero, without affecting the power transmission.</p><p>The protection system can only compensate automatically for the fundamental frequency (50Hz), and manually for the 3<sup>rd</sup>, 5<sup>th</sup>, 7<sup>th</sup> and 9<sup>th</sup> harmonics. In most cases, when the harmonics are very small it is not necessary to compensate for them. There are though cases when compensation for the harmonics is necessary.</p><p>This thesis focuses on finding the best method to extract the content of a sampled signal regarding both simplicity and speed. Both amplitude and phase of each harmonic must be calculated. Is the proposed method suitable for the current computer system and how can it easily be implemented.</p><p>Because the fundamental frequency is known and the harmonics are all multiples of the fundamental frequency it makes the task less complex. It is not necessary to use the FFT algorithm. The DFT can be calculated using correlation. Both phase and amplitude can be calculated very precisely with few samples and not so many computer operations.</p>

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