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Universal inverter for multi-phase low-voltage drives
Pitner, Tomáš ; Pazdera, Ivo (referee) ; Knobloch, Jan (advisor)
The diploma thesis deals with the design and construction of a six-phase low-voltage high-current inverter. Overall design and calculation of the power components of the inverter including its cooling is performed, along with the control circuitry including the inverter leg drivers, the driver and autonomous control of the brake chopper and the interface circuit between the external control circuit and the drivers. In relation to the power components design, research of current distribution between paralleled MOS-FETs and paralleled inverter legs is conducted, leading to the theory of symmetrizing current transformers, for which numerical simulations and verification measurements are done. The thesis also deals with design of a DC bus capacitor -- dependence of the ESR on frequency and temperature for an electrolytic capacitor is measured and the harmonic spectrum of the capacitor current for SVPWM is calculated by numerical simulation. Finally, the construction of the inverter and its testing and measurements are described.
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Influence of skin effect, proximity effect and air gap on winding losses of HF inductors and transformers
Pitner, Tomáš ; Cipín, Radoslav (referee) ; Martiš, Jan (advisor)
The bachelor's thesis deals with power losses in the windings of high-frequency inductors and transformers. A detailed mathematical and qualitative analysis of the skin effect, proximity effect and leakage flux of air gap is performed, supplemented with the results of computer simulations using the finite element method. The thesis introduces analytical and numerical methods for calculating power losses in the windings of inductors and transformers and describes suitable measurement methods, which are further used in the thesis. For selected geometries of inductors and transformers, AC resistances of their windings are calculated using FEM and the results are compared with measurements on constructed prototypes. The winding geometries are also compared between each other.
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Influence of skin effect, proximity effect and air gap on winding losses of HF inductors and transformers
Pitner, Tomáš ; Cipín, Radoslav (referee) ; Martiš, Jan (advisor)
The bachelor's thesis deals with power losses in the windings of high-frequency inductors and transformers. A detailed mathematical and qualitative analysis of the skin effect, proximity effect and leakage flux of air gap is performed, supplemented with the results of computer simulations using the finite element method. The thesis introduces analytical and numerical methods for calculating power losses in the windings of inductors and transformers and describes suitable measurement methods, which are further used in the thesis. For selected geometries of inductors and transformers, AC resistances of their windings are calculated using FEM and the results are compared with measurements on constructed prototypes. The winding geometries are also compared between each other.
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Agile methodologies in complex environment
Balada, Jakub ; Buchalcevová, Alena (advisor) ; Pitner, Tomáš (referee) ; Antlová, Klára (referee)
Only a small number of projects of information system development succeed. Agile methodologies have contributed to a higher level of success of specific projects developed by small teams. Nevertheless, most IT companies still refuse this approach with large-scale projects. This paper comments on the conditions that must be fulfilled for agile adoption, analyzes the limitation of such processes, and describes the approaches for the solutions of such problems with the focus on projects in a complex environment. By means of a case study, the next part of the paper shows the advantages of adopting an agile approach in a real project in a complex environment, which is in conflict with the so far presented limitations of this methodology. The project was evaluated as a success, primary, due to the implementation of the agile methodology during the development phase. This implementation helped meet all the project deadlines, accelerate bug-fixing, and especially deliver functionalities which brought an additional value to the customer. Based on the findings of the case study, the procedures and practices extending the chosen agile methodology are defined. Such procedures and practices can be used in other projects in complex environments in the future. Thus, the paper shows more options for the use of these methodologies, which may help its wider use in the future and hence increasing the success of projects focused on the development of information systems. Such situation would lead to an effective interconnectedness of ICT and business strategies, especially due to the flexible delivery of currently needed ICT services.
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Cloud computing services in Czech republic
Veber, Jaromír ; Doucek, Petr (advisor) ; Čapek, Jan (referee) ; Pitner, Tomáš (referee) ; Karpeta, Jiří (referee)
Modern approaches of providing services such as cloud computing are increasingly used worldwide, and it is a promising way to provide information technology services. Cloud computing promises to increase the efficiency of the management of information technology services, optimize costs and also allows rapid deployment of IT services. The aim of this work is to find where to utilize cloud computing services in the Czech Republic, and how. The objectives were realized through research. Subsequently based on the results of this research there is proposed a model for selecting cloud management solutions for businesses in the Czech Republic. Studies were conducted, among others, in form of a questionnaire survey aimed to analyze the current situation and to deliver data for subsequent analysis of the interaction between the factors that may affect the organization during selection of cloud solutions. Further research was focused on the analysis of the conditions of the Czech Republic in terms of cloud computing and to find differences that distinguish the Czech Republic from other countries around the world. The thesis brings realization of the proposed model that will help organizations to decide whether and how to use cloud services, an overview of the current situation and analysis of the specifics that affect cloud services in the Czech Republic.
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