The subject matter of this paper refers to vibroacoustic measurements of high power transformers. The evaluation method of the transformer technical condition, based on the measurements of mechanical vibrations of its...
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ISBN:
(纸本)9781627480000
The subject matter of this paper refers to vibroacoustic measurements of high power transformers. The evaluation method of the transformer technical condition, based on the measurements of mechanical vibrations of its tub, is characterized. The elements of the measuring set-up, which were used during the registration of the signals coming from the core and winding vibrations of a given transformer unit, transferred by the tub, are presented. Based on the criterion values of the vibroacoustic parameters measured: root-mean-square value of the vibration acceleration and the vibration spectrum amplitude in the frequency range from 0 to 3000 Hz, the evaluation of the technical condition of the power appliance under study was carried out.
The paper presents the measurement results of the noise level of a power transformer. The noise sources occurring in the transformer are presented, and the method applied and the measuring tools used are characterized...
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ISBN:
(纸本)9781627480000
The paper presents the measurement results of the noise level of a power transformer. The noise sources occurring in the transformer are presented, and the method applied and the measuring tools used are characterized. The measurements were taken in 29 points located around the transformer. The evaluation of noise was carried out based on the revised coefficient of the acoustic pressure level. The research work results presented enable the evaluation of the influence of the noise of the unit under study on its environment and make it easier to diagnose the degrees of wear of the fans installed in transformer coolers.
The paper will present the wavelet analysis results using continuous and discrete wavelet transforms of vibrations of a power transformer tub installed on the block of a conventional, thermal condensation power statio...
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ISBN:
(纸本)9781627480000
The paper will present the wavelet analysis results using continuous and discrete wavelet transforms of vibrations of a power transformer tub installed on the block of a conventional, thermal condensation power station. The research tests were carried out during a regular transformer operation in industrial conditions. The measurements were taken from the point of view of the evaluation of the influence of the vibrations registered on the analysis results of the acoustic emission signals generated by partial discharges that can occur in paper-oil insulation systems of power transformers. Moreover, the analyses carried out were supplemented with the research results obtained in laboratory conditions during the measurements taken in the high-voltage testing station of high-voltage power appliances. The influence of the loosened screws fastening the lid of the transformer tub on the time-frequency analysis results obtained of the vibrations registered was investigated. Moreover, the range of the research work carried out referred to the evaluation of the influence of the changes of the pressure force of the metal plates forming the transformer core on the vibration measurement results were obtained. In summary, the evaluation of usefulness was presented and the range of the time-frequency analysis application possibilities, and especially wavelet transforms, in diagnostics of power transformers using the acoustic methods was characterized.
The paper presents research results of electrokinetic zeta potential that exists in the electrical double layer on the border of the solid and liquid phases. For zeta potential examination, samples in the colloid form...
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The paper presents research results of electrokinetic zeta potential that exists in the electrical double layer on the border of the solid and liquid phases. For zeta potential examination, samples in the colloid form were used, the continuous (dispersing) phase of which was constituted by dielectric liquid mixtures formed on the base of simple hydrocarbons (hexane, cyclohexane, toluene), and the solid (dispersed) phase was constituted by materials in a disintegrated form (aluminum, copper, steatite, Al-70). The measurements were taken with Zetasizer 2000 - by Malvern Instruments (UK). Volume density of charge qw on the border of the solid and liquid phases, responsible for generation of electrostatic charges, was determined based on the measured zeta potential and physicochemical properties of the liquids under study.
In this paper, a design of the 3-phase, 6-stator-pole and 4-rotor-pole, 15 kW switched reluctance motor for the propulsion system of the electric vehicle is presented. Its performance such as the torque per volume and...
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ISBN:
(纸本)8986510081
In this paper, a design of the 3-phase, 6-stator-pole and 4-rotor-pole, 15 kW switched reluctance motor for the propulsion system of the electric vehicle is presented. Its performance such as the torque per volume and its efficiency are compared to the machine which is designed based on the conventional design guideline.
In this paper a method to estimate the initial rotor position of the switched reluctance motor (SRM) at the stand still condition is proposed. The proposed method can be implemented by the simple microcontroller based...
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ISBN:
(纸本)8986510081
In this paper a method to estimate the initial rotor position of the switched reluctance motor (SRM) at the stand still condition is proposed. The proposed method can be implemented by the simple microcontroller based system, and it is not necessary to know the magnetization curves. The impulse gate drive signal is applied and the winding current is detected and its approximate value is used for calculating the rotor position. The compensation method to reduce the estimation error thorough one cycle is also mentioned. The proposed method is implemented with the 6-stator-pole and 4-rotor-pole, 1.5 kW 3-phase switched reluctance motor.
Schema mappings play a central role in both data integration and data exchange, and are understood as high-level specifications describing the relationships between data schemas. Based on these specifications, data st...
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Schema mappings play a central role in both data integration and data exchange, and are understood as high-level specifications describing the relationships between data schemas. Based on these specifications, data structured under a source schema can be transformed into data structured under a target schema. During the transformation some structural constraints, both context-free (the structure) and contextual (e.g. keys and value dependencies) should be taken into account. In this work, we present a new formalism for the schema mapping specification. We propose a new class of tree-pattern formulas in order to extend semantics of XML schema mappings by specification of key constraints and value dependencies. We discuss foundations of the method and propose a key-preserving transformation algorithm.
The influence of bother measures the extent to which a user would be bothered or annoyed by any interaction with the agent, especially when the user interacts over the Internet. This paper discusses the model of bothe...
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In our paper we are proposing a complex model of the student (learner) in a virtual educational environment, supported by a multi-agent system. The whole system is centered on the student and it mainly takes into acco...
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In our paper we are proposing a complex model of the student (learner) in a virtual educational environment, supported by a multi-agent system. The whole system is centered on the student and it mainly takes into account Vygotsky's socio-cultural theory that states that social interaction plays a fundamental role in the development of cognition. The model is part of a larger project - DANTE - Socio-Cultural Models implemented through multi-agent architecture for e-learning - that has as main objective the development of a student centred framework for the virtual educational universe that facilitates collaborative learning. The virtual educational world is inhabited by agents: human agents and artificial agents that interact. Agents can be mediating agents, semiotic agents or social agents;they can be intelligent software entities or simple ones, like interface agents.
This paper presents an analysis how the pulses in the long three-conductor coupled lines with common screen interact mutually. The interaction of pulses appears in those places of the line, where there is a change in ...
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This paper presents an analysis how the pulses in the long three-conductor coupled lines with common screen interact mutually. The interaction of pulses appears in those places of the line, where there is a change in characteristic impedance causing a change in reflection coefficient for pulses moving along the line. An exemplary analysis is conducted for a homogenous lossless line both at its starting and terminal point. The results of the analysis are analytical expressions describing quantitative interactions of pulses. The expressions are verified numerically and experimentally involving measurements of the real-life line. The mutual interaction of pulses can be useful in location of faults in electric power lines by means of the pulses method.
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