Ethylene propylene rubber (EPR) cable has been extensively used for distribution of power. The insulation of cable should withstand electrical, thermal, mechanical, and chemical stresses during its operation. It is imperative to measure the data providing dielectric strength of EPR cable for these stresses. Significant improvements on the quality of insulation have been progressing for better performance of cable under these stresses. This study deals with ac voltage stress imposed on the cable. The electrical breakdown strength of 5kV EPR cable under ac voltage has been measured by constructing a suitable test set in Mississippi State University High Voltage Lab.

The thesis deals of microprocesor controlled instrument for measuring. In general it is about of controlling instruments and their usage in standard industry. laboratories and measuring systems. The first part contens theoretical knowledge of controlling instrument, his funtions and describes circuitry of sources of AC voltages. This part describes blocks of instrument and basis connecting in system of instrument. Each block is described with examples in praxis. Examples contents typical connecting and their problems out of view in parameters of instrumenr. In this part is whole theory of analysis and practical using separately parts of instrument. Next part is aimed at searching of interrelationship between the teoretical model of source that described by different circuits and practical connections with electronic parts. These part analyse concrete design with exactly sized parameters and connections. In last part contents describing of measuring at prototype. The appendix contains schematics and boards with electronic parts and test reports of measuring output voltage and frequency with required accuracies.

No description available.

It is common practice to perform accelerated aging with 60 Hz ac to determine the lifetime characteristics of insulation used in the machine. Comparable breakdown measurements are performed at different voltage levels and temperatures for the polyimide insulated machine winding under normal operating conditions of 60 Hz ac. The result shows that the time to failure can be represented by the inverse power law and the Arrhenius equation with respect to test voltage and temperature respectively. However, the use of power electronic devices causes harmonics, and spikes that electrically degrade the machine winding insulation. Applied high frequency pulse voltages can be used to study the impact of electrical degradation of the machine winding insulation that exists in electrical machines. Evaluation of change in dielectric strength, partial discharge and breakdown voltage is monitored versus aging caused by high frequency pulse voltage at 90% of operating temperature.

The thesis deals with a problems of measuring small alternating voltage. The aim of the thesis is to explain in general problems of influences on measurement of small alternating voltage and to carry out a concrete measurement according to instructions of CMI. In the next part the thesis deals with the problems of uncertainties for measurement of small AC voltage and a concrete calculation of uncertainties has been made for measurement made in the first part of this thesis.

nÃo hà / Neste trabalho à apresentado um estudo sobre as caracterÃsticas de magnetizaÃÃo estÃtica de um MRRV â Motor Rotativo de RelutÃncia VariÃvel â de 1 cv, com base na simulaÃÃo do projeto da mÃquina utilizando AnÃlise por Elementos Finitos (AEF) 3D com malhas tetraÃdricas e hexaÃdricas, com vistas a investigar a que mais adequava-se a esse estudo. TrÃs mÃtodos experimentais foram utilizados para a validaÃÃo do projeto via Elementos Finitos: mÃtodo de determinaÃÃo da impedÃncia com tensÃo CA, mÃtodo do tempo de subida de corrente DC de fase e mÃtodo do tempo de descida de corrente DC de fase. Um estudo comparativo foi realizado como forma de efetivar a validaÃÃo. Todas as tarefas de simulaÃÃo e de mediÃÃo foram realizadas utilizando um microcomputador. Para a realizaÃÃo da simulaÃÃo do projeto foi utilizado um software de simulaÃÃo numÃrica com anÃlise dos Elementos Finitos (CST STUDIO SUITE TM 2010Â) em trÃs dimensÃes, utilizando para tanto, malhas tetraÃdricas e hexaÃdricas. Para as tarefas de mediÃÃo, foi utilizada tambÃm uma placa de aquisiÃÃo de dados (DAQ) integrada a duas interfaces: do LabView e Signal Express ambos desenvolvidos pelo o mesmo fabricante da placa de aquisiÃÃo (National Instruments) com o objetivo de determinar a indutÃncia por fase do MRRV. A partir dos valores obtidos de indutÃncias por fase, foi calculado o fluxo concatenado por fase. GrÃficos de fluxo concatenado por corrente e perfis de indutÃncias para sete posiÃÃes sÃo apresentados e entÃo comparados com a simulaÃÃo por AEF. Tabelas evidenciando as diferenÃas de alguns valores entre os mÃtodos em termo de porcentagem sÃo apresentadas e discutidas. Uma avaliaÃÃo sobre todos os mÃtodos foi feita, evidenciando aspectos positivos, negativos, limitaÃÃes e sugestÃes de melhoria dos mesmos. A mÃquina estudada foi um Motor Rotativo de relutÃncia VariÃvel 6/4 (6 pÃlos no estator e 4 pÃlos no rotor), trifÃsico, de 1 cv de potÃncia, corrente nominal de 10A e velocidade de 2.000 rpm, projetado pelo Grupo de Pesquisa em AutomaÃÃo e RobÃtica do Departamento de Engenharia ElÃtrica da Universidade Federal do CearÃ. / This paper presents a study on the characteristics of a static magnetization VRRM - Variable Reluctance Rotating Motor â 1 hp, based on the simulation of machine design using Finite Element Analysis (FEA) with 3D tetrahedral and hexahedral meshes intending to investigate which meshes is the most suited to this study. Three experimental methods to validate the design via Finite Elements were used: method for determining the impedance with AC voltage, the rising time method of DC current phase and falling time of DC current phase method. All tasks of simulation and measurement were performed using a personal computer. To perform the design simulation a numeric simulation software was used with finite element analysis (CST STUDIO SUITE TM 2010Â) in three dimensions, using both, tetrahedral and hexahedral meshes. For measurement tasks also a data acquisition board (DAQ) integrated with two interfaces was used: the LabView and Signal Express both developed by the same manufacturer of the acquisition board (National Instruments) aiming to determine the inductance per phase of the VRRM. From the values obtained of inductance per phase the flux linkage per phase was calculated. Graphs of flux linkage with current and inductance profiles for seven positions are shown and compared with the simulation FEA. Tables showing the values of some differences between the methods in terms of percentage are presented and discussed. An evaluation of all methods was done, showing positives and negatives aspects, limitations and suggestions to improve them. The machine was a studied Variable Reluctance Rotating Motor 6/4 (6 stator poles and 4 poles on the rotor), three-phase, 1 hp, rated current of 10A and speed of 2.000 rpm, designed by the Research Group on Automation and Robotics, Department of Electrical Engineering, Federal University of CearÃ.

This thesis proposes a new bidirectional three-phase AC-DC power converter using matrix converter and Z-source inverter topologies. Advantages of the AC-DC matrix converter are the inherently controllable power factor, the tight DC voltage regulation, the wide bandwidth with quick response to load variation, the single-stage buck-voltage AC-to-DC power conversion; advantages of the z-source inverter are the increased reliability by allowing the shoot-through between upper and lower power switches of one inverter leg, insensitivity to DC bus voltage due to the extra freedom of controlling DC-link voltage. The proposed Matrix-Z-source converter (MZC) marries up both advantages of AC-DC matrix converter and Z-source inverter. It can achieve voltage-boost DC-AC inversion capable of variable voltage variable frequency (VVVF) AC output; it can achieve voltage-buck AC-DC rectification capable of inherent control over AC current phase angle and DC output regulation with a (VVVF) AC source supply. Both foresaid performance in DC-AC inversion and AC-DC rectification can be implemented in a simple open-loop control manner. Three constraints of VSI, in the bidirectional AC-DC power conversion, are the peak AC voltages are always less than DC-link voltage, closed-loop control has to be employed when DC regulation and/or AC current phase angle control are required, and AC voltage is sensitive to the variation of the DC-link voltage in DC-AC inversion. The voltage-boost inversion and/or voltage-buck rectification of MZC overcomes the first constraint; thus MZC enables the AC machine voltage increased higher than DC-link voltage hence advantages of running AC machine at relatively high voltages are enabled. The direct DC voltage regulation and inherent AC-current-phase-angle control of MZC overcomes the second constraint in an open-loop manner; hence a simplified system design is obtained with sufficient room for the further improvement by closed-loop control schemes. The extra freedom in controlling DC-link voltage of MZC overcomes the third constraint hence a DC source voltage adaptable inverter is obtained. This thesis focuses on the study of the feasibility of the proposed MZC through theoretical analysis and experimental verification. At first, the proposed MZC is conceptually constructed by examining the quadrant operation of AC-DC matrix converter and Z-source inverter. After the examination of the operating principles of both AC-DC matrix converter and Z-source inverter, the configuration of MZC is then proposed. The MZC has two operating modes: DC-AC inversion and AC-DC rectification. Circuit analysis for both operating modes shows that the new topology does not impose critical conflict in circuit design or extra restriction in parameterization. On the contrary, one version of the proposed MZC can make full advantage of Z-source network components in both operating modes, i.e. a pair of Z-source inductor and capacitor can be used as low-pass filter in AC-DC rectification. The modulation strategy, average modeling of system, and features of critical variables for circuit design of the proposed MZC were examined for each operating mode. Simulations of the proposed MZC and its experimental verification have been presented. Analytical models of conduction and switching losses of the power-switch network in different operating mode have shown that the losses in the MZC compare favorably with conventional VSI for a range of power factor and modulation indices.

In the fast growing field of Telecommunications, the back up DC power supply plays a vital role in powering the telecom equipment. This DC power supply is a combination of AC-DC Rectifier coupled with a battery bank to support the load when AC input is not available. Figures 0.1 and 0.2 show the line diagram of the DC power supply. The power supply is the most critical element in a telecom installation and it should be highly reliable in order to have un-interrupted service. (Fig) Besides reliability, power density and cost are the driving forces behind the success of a power supply in the market. Off late, the reach of telecom in the society is very wide covering remote villages and major metros. Given this environment, the power supply is exposed to extreme input conditions. It is desirable to design the power supply capable of withstanding wide AC input conditions. Another advantage is that the rectifier unit will keep the battery charged so that the battery will have long life. This thesis is aimed at designing a 1400W (56V/25A) telecom power supply, keeping in view of the issues expressed above. The aim is to design a Switched Mode Rectifier (SMR) that tolerate wide input voltage variations (90Vac to 300Vac). In addition, the design covers unity input power factor, high efficiency (> 90%), high power density ( ), parallel operation and low cost ( ). Chapter 1 of this thesis covers the context and motivation of the work. Chapter 2 presents the design issues pertaining to power supplies. The normalized description of the power converters is presented. Such a description enables one to compare several circuit topologies in order to make effective design decisions. In a similar way the effectiveness of the switches and mgnetics are presented to enable design decisions in the output stage of the rectifier. Chapter 3 presents the design of the 1400W telecom power supply, keeping in view of the stated specifications. The performance results of the converter are presented in Chapter 4. All the design goals have been met. The design exercise has also given insights into possible further improvements. Contributions from this work and course of future development work are indicated in the concluding chapter.