Search

In this study, the effect of 0.75 weight percent filler silica (SiO 2 ) with PI or PA nanowires for dielectric properties of epoxy resin EPOXYLITE 3750 LV (ER) was studied. For this purpose, direct unidirectional conductivity measurements and broadband dielectric spectroscopy measurements were used to describe changes in the dielectric responses of ER/SiO 2 nanocomposites with nanowires in the frequency and temperature range. The presence of nanowires and nanoparticles in the epoxy resin affected the segmental dynamics of the polymer chain and altered the charge distribution in the system. These changes caused a change in permittivity values and a shift in local relaxation peaks in the imaginary permittivity and dissipation factor spectra of nanocomposites. Experiments have shown that temperature-dependent transitions of electrical properties in nanocomposites are associated with to relaxation processes.

The paper presents experimental diagnostics of the oil-paper insulating system of power transformers using progressive frequency method. The first part of the paper deals with the basic information about diagnostics of power oil transformers. The second part of the paper deals with the use of frequency domain spectroscopy (FDS) for power oil transformers. This method is used in the analysis of insulating condition of power transformer with the system of oil-paper. It was found that the results of these tests are highly influenced by the operating temperature during the experimental measurement. Moisture and conductivity between the insulating transformer paper and oil in an insulating system are highly dependent on the temperature. In the other part, the paper presents experimental results of the diagnostic measurement for a real traction oil transformer at different operating temperatures and states (with oil and without). Finally, the paper presents comparative measurement among several autotransformers with the same power. In experimental measurements, the correlation between the measured values and the operational aspects of the individual oil autotransformers are shown.

The first part of paper deals with the base information about diagnostics of power transformers. In this part are presented differently insulating methods, for example method of recovery voltage method, method of polarization and depolarization currents and chromatographic analysis.The second part of paper deals use of method of frequency domain spectroscopy for oil power transformers. This method is used in analysis insulating condition of power transformer with system of oil-paper. It was found, that the results of these tests are highly impacted by the operating temperature during the experimental measurement. Moisture and conductivity between insulating paper and oil in an insulating system are highly dependent from temperature.In the other part, the paper presents experimental results of the frequency diagnostic measurement for a real single-phase traction transformer 110/27 kV at different operating temperatures and states (with oil and without).Finally in the last part, the paper presents comparing frequency insulating measurements among several the same single-phase transformers 110/27 kV.

Nowadays detection of deterioration of electrical motors is an important topic of research. Vibration signals often carry diagnostic information of a motor. The authors proposed a setup for the analysis of vibration signals of three-phase induction motors. In this paper rotor fault diagnostic techniques of a three-phase induction motor (TPIM) were presented. The presented techniques used vibration signals and signal processing methods. The authors analyzed the recognition rate of vibration signal readings for 3 states of the TPIM: healthy TPIM, TPIM with 1 broken bar, and TPIM with 2 broken bars. In this paper the authors described a method of the feature extraction of vibration signals Method of Selection of Amplitudes of Frequencies – MSAF-12. Feature vectors were obtained using FFT, MSAF-12, and mean of vector sum. Three methods of classification were used: Nearest Neighbor (NN), Linear Discriminant Analysis (LDA), and Linear Support Vector Machine (LSVM). The obtained results of analyzed classifiers were in the range of 97.61 % – 100 %.

[EN] Electric motors use about 68% of total generated electricity. Fault diagnosis of electrical motors is an important task, because it allows saving a large amount of money and time. An analysis of acoustic signals is a promising tool to improve the accuracy of fault diagnosis. It is essential to analyze acoustic signals to assess the state of the motor. In this paper, three electric impact drills (EID) were analyzed using acoustic signals: healthy EID, EID with damaged rear bearing, EID with damaged front bearing. Three angle grinders (AG) were analyzed: healthy AG, AG with 1 blocked air inlet, AG with 2 blocked air inlets. The authors proposed a method for feature extraction: SMOFS-NFC (Shortened Method of Frequencies Selection Nearest Frequency Components). Acoustic features vectors were classified by the nearest neighbor classifier and Naive Bayes classifier. The classification accuracy were in the range of 89.33¿97.33% for three electric impact drills. The classification accuracy were in the range of 90.66¿100% for three angle grinders. The presented method is very useful for diagnosis of bearings, ventilation faults and other mechanical faults of power tools. It can be also useful for diagnosis of similar power tools., This work was supported in part by Generalitat Valenciana, Conselleria de Innovacion, Universidades, ' Ciencia y Sociedad Digital, (project AICO/019/224).

Experimental analysis and diagnostics of insulating system oil-paper for traction transformer by frequency method is presented in the paper. In the first part of the paper, the base theory about measurement and diagnostics insulating part (oil and paper) of transformers is described. In the other part of the paper, experimental results of the diagnostic measurement for the traction transformer at a constant temperature using to diagnostic method - frequency domain spectroscopy (FDS) are presented. This method is used for the analysis of insulating conditions of high-voltage equipment with insulating oil paper. Quality of paper moisture and oil conductivity of the transformer - before and after its drying was compared.

The utilization of magnetic nanoparticles in the area of medicine is able because of their biocompatibility, non-toxicity, and common use in several medical applications. Biocompatible magnetic fluids are used for diagnostics and therapy in medical applications, in pharmacy, and in biosensors. These fluids are used as a delivery system for anticancer agents in a locoregional tumor therapy-magnetic drug targeting and hyperthermia. The water-based magnetic fluid is constituted by coating the small magnetic nanoparticles with oleic acid and further dispersion in water. For the study of the influence of an external magnetic field on the aggregation processes of magnetic nanoparticles in biocompatible magnetic fluids, acoustic spectroscopy as a useful tool was used. The goal of the article is to bring new information about the creation of structures in the presence of different application processes of magnetic fields and the temperature of the investigated biocompatible fluid.

In the article is presented experimental analysis and diagnostics of insulating system oil-paper for power transformers, mainly by progressive frequency method – dielectric spectroscopy. In the 1-st part of the article is described base theory about measurement and diagnostics insulating part (oil and paper) of power transformers. In the 2-nd part of article is described measuring method of insulating frequency diagnostics - frequency domain spectroscopy (FDS). This method is used for analysis insulating condition of high-voltage equipment with insulating oil-paper. In the 3-st part of article is described measuring time method of insulating diagnostics - return voltage measurement (RVM). This method is used for analysis of condition of paper moisture of high-voltage equipment. The both measuring methods are unique in terms of analysis of insulating system of oil power transformers. In comparison with other methods, the RVM and FDS methods it is possible comparison and evaluate the moisture state of the dielectric paper of the power transformer with high reliability and accurate. Their reliability in determining moisture in paper was shown by determining the same result (3.5%) on the same measured distribution transformer.

The article examined an temperature effect on the analysis for AC relaxation time of a dumped a material cellulose with synthetic ester and nanoparticles from water with a content of humidity of 5% from weight. It was established that in the range of temperature 253 – 323K, the relaxation time of activation energy is ΔE≈(0.752±0.0268)eV.

The paper is focused on analyses of online diagnostics with analysis of induction motor, transformer and AC generator by means of thermovision measurement. In the 1-st part of article is performed theoretical analysis of thermovision measurement on the base infrared thermal radiation. In the 2-nd part of article is performed experimental diagnostics and analysis by thermovision camera on induction motor, high-voltage transformer and AC generator. In the end are performed conclusions according to measured values by the means of thermovision analysis.

This article describes evaluation principles electronic components in ignition system by using with voltage, current and thermovision analysis. The first of article is focused on theoretical principles of activity of ignition system based on voltage behavior in time for the primary part winding of transformer. In the second part of article is experimental measurement by means of measurement of voltage waveforms and no-contact measurement of thermal field by thermovision camera. In the end of article is performed comparison of both methods and detected the same fault in the part of components of the measured equipment. Both diagnostic methods have certain limitations, as the high-voltage coils and spark plugs are housed in encapsulated metal containers. The biggest problem can occur with thermal imaging diagnostics. If the ignition system is completely inaccessible, it is only necessary to use diagnostics by measuring high-voltage and current pulses by connecting clamp probes.

In the 1-st part of article is presented theory about diagnostic methods for transformer construction (winding, taps and feromagnetic core). In the 2-nd part of article is presented experimental analysis of fault in winding of transformer by means of method of impact test and frequency response analysis (SFRA). For transformer diagnostics and analysis of winding quality are very important these methods by measurement in time and frequency domain using by impact test and method SFRA. Differences between measured frequency curves are analyzed by value of relative factor Rxy

Currently, the control circuits check the condition of electronic components mainly by monitoring voltage levels, calculating and estimating value limits during the diagnostic mode of the element. In this article, we will focus specifically on the ignition system. Specialized measurements were made on the proposed measurement systems by simulating faults by applying oil and gasoline between the electrodes and failing to make the ignition contact of the driver on the spark plug.

Polarization and relaxation processes in a magnetic fluid can be characterized by the complex permittivity and dissipation factor. The change of these parameters and rearrangement of magnetic nanoparticles in an electric field and magnetic flux density were studied by dielectric spectroscopy. The frequency dependences of dielectric parameters were measured in a wide frequency range from 1 mHz to 10 kHz at a wide range of temperatures from −35 °C to 35 °C at the application of the magnetic flux density and the electric field by a capacitance method. The object of our study was the magnetic fluid based on transformer oil TO 40 A MOL with FeO·Fe 2 O 3 magnetic nanoparticles. The development of the dissipation factor of studied magnetic fluid show one low-frequency relaxation maximum at the eigenfrequency, which was associated with the electric double-layer. The Cole-Cole relaxation model was used for analyzing measured data, and the activation energy from the Arrhenius plot was calculated.

This article describes principles of evaluation of individual parts of the ignition system, using conventional diagnostic systems, based on evaluation of current and voltage waveforms. By means of the practical test, diagnostics, measurements and subsequent analysis it was proved that thermovision plays an important role in diagnostics in on-line check automotive equipment. By comparing the non-standard warming behaviour of a part of the electrical system with combination with time high-voltage method, it is possible to diagnose a fault and also check the operating mode of the system. An example of a thermogram of the temperature distribution of the ignition coils and analysis of high-voltage ignition curves with faulty spark plugs is given in part of paper of nondestructive diagnostics with a difference in temperature. Analysing fault condition of ignition systems, using method conventional diagnosis of high-voltage pulse waveforms and also method of thermovision diagnostics, we can adequately evaluated the functionality of the electronic system and its individual components. In some cases, with one coil ignition systems, we cannot use the conventional method and therefore it is preferable to proceed to the analysis of temperature fields.

Currently, the control circuits check the condition of electronic components mainly by monitoring voltage levels, calculating and estimating value limits during the diagnostic mode of the element. In this article, we will focus specifically on the ignition system. Specialized measurements were made on the proposed measurement systems by simulating faults by applying oil and gasoline between the electrodes and failing to make the ignition contact of the driver on the spark plug.

Paper presents experimental diagnostics of insulating system oil-paper for power transformers, mainly by progressive frequency method – dielectric spectroscopy. The introduction of the article is described the base analysing for measurement insulating elements (oil and paper) of power transformers. The next part of article is described application of dielectric frequency domain spectroscopy (FDS) method for high-voltage power transformers. Diagnostic methods are used for measurement of insulating state of high-voltage devices with insulating parts as oil-paper. It was present that the values of these measuring results are highly impacted by the temperature of operating during the experimental diagnostics. Conductivity and moisture between dielectric transformer paper and insulating oil in an dielectric system are highly dependent from internal and ambient temperature. In the final section the article are presented experimental values of the diagnostic analysis for an operating oil traction transformer at different internal temperatures and conditions (with oil filling and without).

This article describes evaluation principles of various parts of the system of ignition through respectable measuring systems based on the evaluation of voltage and current waveforms. Practical tests, measurements, diagnostics and following analyze have shown that thermal imaging plays an important role in the diagnosis of online car controls. If will be compared the non-standard heating of a part of the electric system with the combination with the high-voltage time measuring method, that is possible to analyze the failure and also monitoring the system operating mode. An example of an ignition coil temperature distribution thermogram and analysis of high voltage ignition curves with error spark plugs is given in the section on non-destructive diagnosis with temperature differences. By analyzing the failure state of ignition systems, using the method of diagnostics of high-voltage pulse behaviors and also the method of thermal imaging diagnosis, it is possible accordingly to review the functional of the electric system and its various components. In some cases, it not possible use the classical method with ignition single-coil system, and it is recommended continues the analysis of temperature fields.

Nowadays, there is a need to reduce emissions in the world and use electricity to drive vehicles. There is an increasing interest in small passenger vehicles suitable for crowded cities. In this paper we try to design a universal control structure for a single-wheeled vehicle with a tilt sensor. This structure can also be applied to a vehicle with parallel wheel arrangement. The paper describes a current and position loop suitable for a single wheeled vehicle. In the paper is designed a simple complementary filter for data processing from the accelerometer and gyroscope and a block diagram of the program for use in any microprocessor.