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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

Effect of stress, antibiotics and phytochemicals on verotoxic isolates of acinetobacter haemolyticus and escherichia coli obtained from water and wastewater samples

Hamuel, James Doughari January 2012 (has links)
Thesis submitted in fulfillment for the requirements for the degree Doctor Technologiae: Environmental Health in the Faculty of Applied Sciences, Cape Peninsula University of Technology, 2012 / Water related issues such as water treatment and distribution have become extremely important all over the world due to population growth, growing urbanization, health and environmental pollutions. Contamination of water bodies especially in Africa with antibiotic resistant bacteria strains is a cause for concern. Escherichia coli O157 H:7, and various strains of non O157 E. coli and Acinetobacter spp. are known for antibiotic resistance. Both bacteria are environmental organisms found coexisting together with high potentials of exchange of resistance genes. Despite the stress conditions confronting these bacteria in water, food and the human body, in the form of disinfectants, antibiotics, salts and the innate immunity, they appear to develop adaptive mechanisms that enable them survive and cause infection. This therefore necessitates the need for investigation of effective virulence factor-targeted control measures. Culture of 62 water samples on Brilliance E. coli/coliform selective medium (BECSM, Oxoid), Eosin Methylene Blue (EMB) agar, or Baumann’s enrichment medium (BEM) and Leeds Acinetobacter Medium (LAM) for the isolation of E. coli and Acinetobacter spp. was carried out. Isolates were investigated for virulence factors, antibiotic resistance and transformation of resistance genes. The effect of oxidative stress exerted by 0.3% Crystal violet, 0.3% Bile salt, 4.0% NaCl, and 8% ethanol on some of the multi-drug resistant strains as well as the effect of stem back extracts of Curtisia dentata on verotoxin production by the verotoxic strains was also investigated. Out of the 69 isolates of E. coli (including O26:H11, O55, O111:NM, 72 O126, O44, O124, O96:H9, O103:H2, O145:NM and O145:H2.) and 41 isolates of Acinetobacter spp. with 26 (53.06%) of the E. coli and 6 (14.63%) of the A. haemolyticus isolates producing verotoxins, and no A. lwoffii isolate produced the toxins. Twenty five - 25(35.23%), 14(20.30%) and 28(40.58%) of the E. coli isolates were positive for VTx1&2, Vtx1 and Vtx2 respectively, 49(71.015%), were positive for extended-spectrum beta-lactamases (ESBLs), 7(77.78%) for serum resistance, 57(82.61%) for cell surface hydrophobicity, 48(69.57%) for gelatinase production and 37(53.62%) for haemolysin production. While transformation occurred among the E. coli and Acinetobacter isolates (transformation frequency: 13.3 x 10-7- 53.4-7), there was poor curing of the plasmid genes, a confirmation of presence of stable antibiotic resistant genes (DNA concentration between 42.7-123.8 μg) and intra-genetic transfer of multidrug resistant genes among isolates. Oxidative stress due to chemicals, salts, alcohol or freeze-thawing (blow temperature stress) exerted various degrees of lethality on E. coli isolates with some bacterial strains losing their potential to express virulence factors with time. There was however, generally insignificant (t test; P≤0.05) lethal effect against all the A. haemolyticus isolates, but crystal violet exerted the highest lethal effect on some individual isolates followed by ethanol, bile salt and NaCl. Isolates from wastewater demonstrated the highest rate of resistance compared to isolates from river water. The cell kill index (CKI) increased as temperature stress (-5; -18; and -28ºC) increased with time. But the rate of loss of expression of virulence factors or viability was slower in isolates from wastewater and abattoir compared to those from river water. Sixty percent of the E. coli isolates showed various levels of resistance to different antibiotics (ampicillin (10 μg), cefuroxime, cephalexin, ceftazidime and tetracycline (30 95 μg in each case)) (multidrug resistance index (MDRI) values 4.20-5.60%). Relative inhibition zone diameters (RIZD) of C. dentata extracts against E. coli serotypes ranged between 8-28% (MIC, 100-2500 μg/ml), while against A. lwoffii and A. haemolyiticus, the RIZD values ranged between 10-28% (MIC, 100-850 μg/ml) and 6-28% (MIC 150-2500 μg/ml) respectively. However, higher MICs (MIC, 70-2500 mg/ml) were recorded for isolates with high MDRI values. Extracts demonstrated inhibitory action against the expression of both Vtx1 and Vtx2 genes in E. coli, A. haemolyticus and A. lwoffii. Saponins, tannins, glycosides, anthraquinones, flavonoids, steroids, phenols quinones, anthocyanins, amines and carboxylic acids were present in C. dentata. Ethanol root bark extracts consistently showed the highest DPPH radical scavenging activity (62.43%), total phenol content (TPH) (57.62 26 mg GAE/g) and reducing power (RP) (41.32%), followed by those of the stem bark and leaf extracts with the respective values of 54.68%, 37.77 mg GAE/g and 21.83%. The extracts also induced the leakage of Na+ and K+ 107 ions from both test bacteria. Detection of virulence factors, antibiotic resistance genes and transformation among these isolates is a very significant outcome that will influence approaches to proactive preventive and control measures and future investigations. Resistant verotoxic A. haemolyticus could further complicate treatment in verotoxic food-borne or nosocomial infections. Induction of cationic leakage by extracts of C. dentata is an indication of one of its mechanism of action on bacterial cells. The plant can therefore be a good source of antibiotic substances for composition as antioxidants or antimicrobials with novel mechanism of action for the treatment of verotoxic bacterial infections.
22

Evaluation of bambara groundnuts (Vigna subterrenea (L.) Verdc.) milk fermented with lactic acid bacteria as a probiotic beverage

Murevanhema, Yvonne, Yeukai January 2012 (has links)
Thesis presented in partial fulfilment of the requirements for the degree of Master of Technology (Food Technology) Department of Food Technology Faculty of Applied Sciences Cape Peninsula University of Technology, 2012 / The aim of this study was to evaluate bambara groundnut milk (BGNM) subjected to fermentation with lactic acid bacteria (LAB) as a probiotic beverage with a view to developing value-added product. Central Composite Rotatable Design (CCRD) was used to optimise the hydration time and temperature of BGN flour for optimum BGN milk (BGNM) production. The optimum time and temperature was 2 h at 25oC. The effect of variety was assessed on the quality and consumer acceptability of BGNM prepared from five varieties of BGN (black, red, brown, brown-eye, and black-eye) which were representatives of the BGN available in South Africa. BGNM from the five varieties differed significantly (p<0.05) in, lightness, chroma, redness, yellowness, hue and antioxidative activity, while the pH were not significantly different. The four BGNM samples were significantly different (p < 0.05) in appearance, colour, mouthfeel and overall acceptability but not in aroma and taste. A three factor design (4 x 3 x 3) consisting of probiotics (Lactobacillus acidophilus, L. bulgaricus, L. casei and L. plantarum), temperature and fermentation time, were used to estimate the optimal conditions for the production of BGN probiotic beverage (BGNPB). The optimal condition for the production of BGNPB was estimated to be 35oC for 24 h with a desirability of 0.854 for L. bulgaricus. The next promising probiotic was L. plantarum that could be fermented at 35oC for 24 h with 0.843 desirability. BGNM from the red variety were fermented with L. bulgaricus and L. plantarum and L bulgaricus (in combination), making plain and sweetened BGNPB which were evaluated for their quality and consumer acceptability. The four BGNPB samples were significantly different (p < 0.05) in aroma, taste, mouthfeel and overall acceptability but not in appearance and colour. The plain BGNPB were assessed for their proximate composition, antioxidant activity, in vitro probiotic tolerance to simulated gastric juices and bile and a 28 days shelf life study at 5, 15 and 25oC. The protein, total dietary fibre (TDF), ash and antioxidative activity of the BGNPB were significantly different while the fat and carbohydrates were not significantly different. Time and concentration of the gastric juice and bile had significant effects on the percentage bacterial survival of probiotics in the BGNPB. However, the probiotics did survive, in low numbers, in the simulated gastric juice and bile after 180 and 240 minutes of incubation. Titratable acidity, pH, microbial load and colour of the BGNPB were significantly affected by the storage time and temperature during the shelf life study. At the 5oC storage temperature the BGNPB had a right censored shelf life on day 28. At 15oC the shelf life was 18 and 10 days for L bulgaricus and L. plantarum and L. bulgaricus respectively. The outcome of this research showed that a novel BGNPB product can be made from fermenting BGNM with LAB.
23

An investigation into the potential of developing an in vitro method for propagating strelitziaceae

North, Jade Joan January 2011 (has links)
Master of Technology: Horticulture in the Faculty of Applied Sciences at the Cape Peninsula University of Technology, 2011 / A study was conducted to investigate the effects of: i) various media compositions and wounding treatments on the in vitro germination, growth and regeneration of Strelitzia reginae plantlets derived from zygotic embryos, ii) antioxidants, plant growth regulator (PGR) concentrations and plant tissue wounding treatments on phenolic compound production. One experiment consisted of 8 medium types including different combinations of Murashige and Skoog (MS) medium strength, activated charcoal and vitamin supplements. Twelve replicates were used for each treatment. In another experiment, germinated plantlets were subjected to 2 wounding treatments; (unwounded explants (control) and explants longitudinally sectioned through the apical meristem). The explants were transferred to ten different regeneration media consiting of different concentrations and combinations of auxin and cytokinin supplements and antioxidants. Ten replicates were used for each treatment. Results indicated the positive role of activated charcoal (AC) in reducing oxidative browning of embryo explants. The highest germination rate of embryos was observed in media containing AC without vitamin supplementation. Germination significantly decreased with the addition of vitamins. With regard to effects of various media compositions and wounding treatments on in vitro growth and regeneration of Strelitzia, significant results were achieved with 1-naphthalene acetic acid (NAA) and 6-benzylaminopurine (BAP) concentrations on explant discoloration and callus formation. The antioxidant treatments, activated charcoal (AC) and ascorbic acid (AA) significantly affected explant discoloration, the induction of callus and the length of roots developed. Wounding treatments affected plant height, increased explant height and callus formation. Interactions between higher NAA and BAP concentrations together with wounding resulted in the most effective treatment in reducing explant discoloration at the media contact point. Furthermore, results showed the various NAA and BAP concentrations to significantly affect phenolic exudation. The media containing the highest PGR concentration resulted in the highest phenol content. AC significantly reduced the total phenol content of media by 53%, compared with AA. Phenolic exudation was significantly increased as a result of explant wounding. Various interactions between the NAA and BAP concentrations, antioxidants and wounding affected phenolic exudation and the total phenol content of media. This study provides insight into the contributing factors and methods of overcoming the major problem of phenolic oxidation and promoting the in vitro growth and regeneration of Strelitzia.
24

The effects of various drip fertigated water quantities on hydroponically cultivated Cucumis sativa L.

Sonnenberg, Donovan Mark January 2012 (has links)
Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Horticulture in the Faculty of Applied Sciences at the Cape Peninsula University of Technology, 2012 / The effects of various water quantities were assessed on Cucumber (Cucumis sativa L.) grown hydroponically in the greenhouse. The objectives of the study were to evaluate influence of water quantities on: i) photosynthesis and chlorophyll content of Cucumis sativa L.; ii) the nutrient uptake in Cucumis sativa L. iii) flavonoid and anthocyanin metabolism in Cucumis sativa L. and iv) growth and yield in Cucumis sativa L. The treatments included 8 various water regimes (2l/h, 4l/h, 6l/h, 8l/h, 10l/h, 12l/h, 14l/h and 16l/h. The plants received water five times a day, making it 10, 20, 30, 40, 50, 60, 70, and 80 litres per day. Results showed that generally the Photosynthetic rate (A), intercellular CO2 concentration (Ci) and stomata conductance (gs) and the transpiration rate of the cucumber plants were significantly increased by increasing water quantities compared with lower water quantities. Additionally, there were significant improvements in leaf colour in weeks 2, 3, 4, 5, 6, 7 and 8. Overall, the foliage colour was improved as water supply was increased. The greener leaves were documented in treatments supplied with higher water doses. Additionally, the chlorophyll content of cucumber plants was increased significantly with varying water quantities. The highest chlorophyll contents were found in plants treated with 16l/h. The fresh and dry weights of roots, leaves and stems were significantly (P≤0.001) influenced by different water quantities supplied to Cucumis sativa L. The largest quantity of fresh roots was recorded in the control treatment (2l/h) in comparison with all other treatments. However, the best growth with regard to fresh and dry weights of leaves and stems were recorded by supplying the water quantities ranging from 10-16l/h. Altering water supply significantly (P≤0.001) affected the uptake of nitrogen, phosphorous, potassium, calcium, sodium, copper, zinc, aluminium and iron in roots of Cucumis sativa L. Irregular results were recorded in the uptake of these nutrients in the roots. However, leaf uptake of N, P, K, Ca, magnesium, sulphur, Cu, Zn, manganese, boron, and Al responded significantly (P≤0.001) to the different water quantities. The best result for each was observed at quantities involving 16l/h. In stems of cucumber water quantities significantly (P≤0.001) affected the uptake of N, P, K, Ca, Mg, Na, S, Cu, Zn, Mn and B. The highest uptake of N, P, Ca, Mg and S were found at the maximum supply of water (16l/h) compared with the control (2l/h). Sodium uptake showed irregular patterns, whereas K and Zinc uptake peaked at 14l/h. The data from this study showed that flavonoid metabolism was not significantly affected by the different water quantities supplied to cucumber plants. However, the anthocyanin content in roots, leaves, and stem was significantly influenced by water levels. The lowest water quantity (2-6l/h) significantly increased the levels of anthocyanins in all tissues tested. Increasing water quantities significantly decreased the anthocynanin metabolism in all tissues. Plant height displayed significant differences with water quantities from weeks 1-8. In week 1, the plant height was superior at supplying 4l/h in comparison with other treatments. In week 2 and 5 irregular trends were detected. At weeks 3 and 4, plants supplied with 8-12l/h displayed superior plant height performance. At weeks 7-8, significant and optimal results were observed at water quantities ranging from 4-16l/h compared with the control treatment. Water quantities significantly (P≤0.001) affected the number of leaves per plant from weeks 2-8. Irregular results were displayed in weeks 2 and 3. At weeks 4 and 5, the highest numbers of leaves were in water quantities of 12l/h and 10l/h, respectively. Generally, leaf numbers increased with increasing water levels from weeks 6-8. Plant vigour was significantly affected by the alteration of water quantities at weeks 1, 2, 4, 5, 6, 7 and 8. At weeks 1 and 4, more vigorous plants were found in the treatments that received from 10-16 l/h. At weeks 2 and 5, optimal results were found at treatments that received from 6-14l/h. At weeks 6, 7 and 8, the most vigorous plants were found at the highest water quantity of 16l/h. With fruit length, fruit width, rind colour, fruit quality (marketable fruit) and weight, results from the harvest done in the first, second and third week showed that water quantities significantly influenced these parameters. Optimal results were reported when the plants were supplied with water ranging between 14-16l/h. During harvesting at week 4, the fruit length, width, rind colour, were of marketable quality at 16l/h. Generally, the plants that received highest amount of water (16l/h) had the highest cucumber yields compared with all other treatments. Higher water quantities in this study resulted in increased physiological responses such as photosynthesis and nutrient uptake which resulted in the higher fruit yields. In water-limited environments, results from this study could assist growers with reasonable cucumber yields while saving water for other farm uses.
25

An analysis of the impact of variation orders on project performance

Ndihokubwayo, Ruben January 2008 (has links)
A DISSERTATION PRESENTED TO THE HIGHER DEGREES COMMITTEE OF THE CAPE PENINSULA UNIVERSITY OF TECHNOLOGY IN FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTERS OF TECHNOLOGY: CONSTRUCTION MANAGEMENT CAPE PENINSULA UNIVERSITY OF TECHNOLOGY, 2008 / This study investigated the impact of variation orders on project performance in order to take proactive measure to reduce them. The study had the following objectives, namely (1) to investigate the prevalence of variation orders on construction projects; (2) to determine the cost impact of variation orders; (3) to examine to what extent variation orders added value to construction projects; (4) to determine whether the activities associated with variation orders may be regarded as waste; (5) to identify the predominant origin agent as well as the causes of variation orders; and (6) to establish the nature and extent of the impact of variation orders on overall project performance. Literature relative to the research area was extensively reviewed. The data gathering approaches included an exploratory study on costs of variation orders on two construction projects, interviews with three top management personnel in construction contracting companies, the audit of site instructions with regard to waste and their value-addedness and self-administered questionnaires. A purposive sampling method was followed to identify participants into the study. The audit of site instructions revealed that most variation orders were beneficial. However, 14% of site instructions had waste associated with them. It was possible to quantify apparent waste associated with variation orders by means of an ‘origin-cause matrix’ designed for that purpose. Problematic situations arising from the occurrence of variation orders included discrepancies between the claimed and certified amounts. Variation orders impacted project performance with regard to cost and time overruns and disputes between parties to the contract. Most variation orders involved additional works. The complexity of works was the most predominant factor influencing the occurrence of variation orders. The reduction of the occurrence of variation orders was traced back to the pre-contract stage given that the most predominant origin agent of variation orders was the client and then due to an unclear brief of works to be executed. Suggestions regarding the reduction of variation orders include (1) adequate planning in advance is required by all involved parties before works start on site, (2) consultants should do a thorough concluding design and working drawings and contract documents should be complete at tender stage, (3) clients should provide clear brief, (4) enhance communication and all parties should be proactive at all times, (5) works should be supervised with an experienced and dedicated supervisor and (6) consultant should ensure that the design/specifications fall within the approved budget and the budget team should be appointed and participate during the design phase. The study suggests further investigation regarding the development of a more equitable basis of valuation of cost recovery which was beyond the scope of this research.
26

Augmentation of a nano-satellite electronic power system using a field-programmable-gate-array.

Cupido, Stephen William John January 2013 (has links)
Thesis is submitted in fulfilment of the requirements for the degree Master of Technology: Electrical Engineering in the Faculty of Engineering at the Cape Peninsula University of Technology 2013 / The CubeSat standard has various engineering challenges due to its small size and surface area. The challenge is to incorporate a large amount of technology into a form factor no bigger than 10cm3. This research project investigates the space environment, solar cells, secondary sources of power, and Field-Programmable-Gate-Array (FPGA) technology in order to address the size, weight and power challenges presented by the CubeSat standard. As FPGAs have not yet been utilised in this particular sub-system as the main controller, this research investigates whether or not the implementation of an FPGA-based electronic power supply sub-system will optimise its functionality by overcoming these size weight and power challenges. The SmartFusion FPGA was chosen due to its analogue front end which can reduce the number of peripheral components required by such complex systems. Various maximum power point tracking algorithms were studied and it was determined that the perturb-and-observe maximum power point tracking algorithm best suits the design constraints, as it only requires the measurement of either solar cell voltage or solar cell current, thus further decreasing the component count. The SmartFusion FPGA analogue compute engine allows for increased performance of the perturb-and-observe algorithm implemented on the microcontroller sub-system as it allows for the offloading of many repetitive calculations. A VHDL implementation of the pulse-width-modulator was developed in order to produce the various changes in duty cycle produced by the perturb-and-observe algorithm. The aim of this research project was achieved through the development and testing of a nano-satellite power system prototype using the SmartFusion FPGA from Microsemi with a decreased number of peripheral circuits. Maximum power point was achieved in 347ms at worst case with a 55% decrease in power consumption from the estimated 330mW as indicated in the power budget. The SmartFusion FPGA consumes only a worst case of 148.93mW. It was found that the unique features of the SmartFusion FPGA do in fact address the size weight and power constraints of the CubeSat standard within this sub-system.
27

Design and development of a battery cell voltage monitoring system

Prinsloo, Nick January 2011 (has links)
A Thesis for The Department of Electrical Engineering in fulfilment of the requirements for the Magister Technologiae degree in electrical engineering, at the Cape Peninsula University of Technology, 2011 / The purpose of this thesis was to design and develop a measurement system that would allow accurate measurement of individual cell voltages in a series cell stack. The system was initially proposed to be used in conjunction with an active cell balancer. This would allow for the efficient equalising of cells as well as provide detailed information on the cell stack and how the stack operates over time. Having a system that measures voltages accurately, with which the active cell balancer can be controlled would allow for peak cell lifetime and performance. Current battery management systems are large, complex and inefficient and a new way of battery management had to be investigated. To accurately measure individual cells in a series stack, the high common mode voltage must be negated. Different techniques that are currently used to create galvanic isolation were reviewed; circuits were designed and were simulated to find the most suitable design. The traditional methods used to create galvanic isolation did not provide adequate results. The methods were too inefficient and not accurate enough to be used. The methods that had the required accuracy were too complicated to connect in a useable system. This led to the investigation of integrated circuits created to measure voltages in large cell stacks. An integrated circuit from Linear Technology was chosen and a system was built. A system was thus designed that fulfilled the most desirable design specifications while delivering excellent results. The system allowed accurate, individual voltages to be measured in the presence of high common mode voltages. Accuracies and measurement time were well below the required system specification. Power consumption was high, but different component choice will lower power consumption to within specification. Excellent results were obtained overall with most, although not all results well below the design specifications. By including current measurements, as well as other technologies such as wireless communication, USB connectivity and a better data processor, this system will be at the forefront of current battery management technology.
28

CubeSat mission design for characterising the dual auroral radar network (SuperDAN) field-of-view

Minko, F Sagouo January 2013 (has links)
Thesis submitted in fulfilment of the requirements for the degree Master of Technology: Electrical Engineering In the Faculty of Engineering at the Cape Peninsula University of Technology, 2013 / The French South African Institute of Technology (F’SATI) at the Cape Peninsula University of Technology (CPUT) began a program in Satellite Systems Engineering in 2009 and is developing its first satellites. The satellites are based on the CubeSat standard, which defines one unit (1U) as a cube with a maximum weight of 1 kg and volume of 1dm3, and can be scaled up to three units (3U) for increased functionality. ZACUBE-1, a 1U CubeSat that is being developed, will be launched into a sun synchronous orbit in 2013. The main payload of the 1U CubeSat under development is a space weather experiment (beacon transmitter). The beacon transmitter is a scientific payload, which is being developed in collaboration with SANSA Space Science (SANSA SS) in Hermanus, South Africa. The beacon signal will be used to characterise the space weather radar antenna array at the South African National Antarctic Expedition (SANAE IV) base in Antarctica. The SANAE IV radar forms part of the SuperDARN (Dual Auroral Radar Network) project. This phased array antenna network comprises 16 radiating elements, with a 3o beam width that can be steered in 16 different directions to span the azimuth sector. These antennas are spread over both the northern and southern hemispheres. They operate in the HF band between 8 to 20 MHz and are used to primarily monitor the convection of the Earth’s magnetic field by monitoring coherent scatter from it. Orbital analyses were conducted to determine how the choice of the orbit affects the coverage of the array’s field-of-view. Propagation analyses were conducted to investigate how space weather variations affect HF signal propagation. The beacon signal will be used as an active target source and will enable the determination of the phase response of the array, thereby determining the direction-of-arrival of the signal. This will allow the experimental verification of the antenna’s beam pattern. The beacon signal prototype board was developed by using an RFID transceiver that operates in the HF band, capable of delivering up to 200 mW. Position determination of the satellite will be done by using two line elements (TLE) data. Experimental data will be available once ZACUBE-1 is in orbit; therefore, the work presented here documents a feasibility study and design of the experiment that will be conducted once the satellite is in orbit.
29

Digital control of a class-D audio amplifier

Quibell, Jason January 2011 (has links)
Thesis (MTech (Electrical Engineering)--Cape Peninsula University of Technology, 2011 / Modern technologies have led to extensive digital music reproduction and distribution. It is fitting then that digital audio be amplified directly from its source rather than being converted to an analogue waveform before amplification. The benefits of using a digital controller for audio processing include being able to easily reconfigure the system and to add additional functions at a later stage. Digital audio is primarily stored as Pulse Code Modulation (PCM) while Pulse Width Modulation (PWM) is the most popular scheme used to drive a class-D amplifier. The class-D amplifier is selected in many applications due to its very high energy efficiency. Conventional PCM to PWM conversion is inherently nonlinear. Various interpolation schemes are presented in this research project which help to address the nonlinearity. Digitally generated PWM has a limited resolution which is constrained by the system clock. This thesis presents noise shaping techniques which increase the effective resolution of the PWM process without having to use an excessively high system clock. Noise shaping allows a low resolution modulator to be used to reproduce high resolution audio.
30

Wireless transformer condition monitoring system

Zandberg, Hermanus Andries Jakobus January 2013 (has links)
The Department of Electrical Engineering in fulfilment of the requirements for the Magister Technologiae in Electrical Engineering at the Cape Peninsula University of Technology November 2013 / Pole mounted transformers (PMT) in rural areas present an opportunity for local utilities to do current monitoring on these systems. These transformers are exposed to abnormal amounts of stress due to the vast power demand in these areas. The aim of this study is to develop a more cost-effective condition monitoring system. Transformer current monitoring can be a dangerous practice if not done by suitably trained utility electricians. Hence this study is partly aimed at the elimination of hazardous working environments associated with manual electrical measurements. An investigation to determine a safe and cost-effective way to obtain the electrical measurements required from PMTs is undertaken. Although current measurements can be done with a current clamp-on meter, these measurements still take place at the phases of the transformer and are unsafe. The possibility of implementing wireless data gathering on current clamp-on meters is therefore investigated. This is made possible by a wireless sensor node (WSN) which gathers information and transmits it wirelessly to a WSN base station. This wireless solution is battery powered, necessitating battery replacements, therefore leading to the investigation of magnetic fields, magnetic materials and magnetic induction. A current clamp able to generate a high voltage (HV) output with minimal magnetic field strength is developed. The magnetic fields produced by the transformer’s phase cables are used to generate an alternating voltage. With the help of a microcontroller and an energy harvesting circuit, this voltage is converted and used to charge supercapacitors. The magnetic fields are also used to determine the current flow in the transformer phase cables when the device is not in energy harvesting mode. The device will then undergo comprehensive laboratory testing to determine its accuracy and durability, and is then used to do ‘real life’ current measurements, the results of which are compared against an off-the-shelf current monitoring device.

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