Icing on the wires of overhead power lines is a big problem to maintain their integrity. The process of icing wires leads to a significant increase in their mass and, accordingly, to large overloads on the wire and electric supports. Exceeding the loads above the permissible ones can cause great damage to power lines. Wires, cables can break, fittings can be damaged and even lead to collapse of electrical poles. At the same time, damage is caused from the undersupply of electricity. This damage may exceed the damage from damage to the elements of power lines. Ice on the wires usually appear in winter, especially when the warming is going to be replaced by a cold snap and the temperature fluctuates around zero. The problem can be exacerbated by strong wind loads. An increase in air humidity also accelerates the formation of an ice "coat" on wires and electrical poles. Under the most unfavorable conditions, the wall thickness of the “fur coat” of ice on the wire can reach more than 70 mm. Such an ice coat can lead to exceeding the maximum permissible loads and damage to the power line, as well as damage from a power outage. The mechanism of ice formation on overhead power lines, as well as negative damage to power lines and high-voltage pylons under the action of ice load, has been studied. An analysis of the known methods of dealing with ice on power lines has been carried out. An innovative device for combating icing formations is proposed. The advantage of the proposed device is the ability to operate in two modes: vibrating and shock-shaking, which expands its functionality. In preventive mode, the device operates continuously due to the interaction with alternating current flowing through the wires of power lines in the normal mode of their operation, without the need for shutdown for maintenance, which gives the electromechanical interactions of devices with the wire of the power line a vibrational character and ensures the continuity of the process of removing water drops from the wires at an early stage before ice formation. Thus, in the preventive mode of operation of the power line, the causes of icing of the wires are eliminated, and not its consequences, which eliminates the need to shut down for maintenance, and reduces the required costs of resources and energy.
The article is devoted to the technology of cold gas-dynamic spraying - a relatively new technology for creating functional coatings in which narrowed-expanding nozzles (De Laval nozzles) are used, in which solid powders are sprayed at or close to supersonic speed in the direction of the substrate, where they plastically deform and adhere. Cold gas dynamic spraying is an innovative process that has received widespread scientific interest and industrial applications in the automotive, aerospace and biotechnology industries in recent years. Spraying various powder materials in this way provides protection against corrosion and can increase the mechanical strength and wear resistance of details. With that method it is possible to create functional coatings with different thermal conductivities and electrical conductivities, which can be used as insulation materials, conducting and isolation surface layers of parts, coatings for controlling gaps, restoring and repairing details. The article discusses modern developments in the field of experimental analysis of technologies and processes of cold gas-dynamic spraying, the systems of cold gas-dynamic spraying and coating formation are determined and the parameters and principles of the process are described. The installation for spraying surfaces developed at VNAU is presented and researches and the analysis of possibility of use of a method of a cold gas-dynamic spraying for restoration of details of autotractor equipment of agricultural purpose are carried out.
The article analyzes various methods of creating polymer coatings. The following methods of application of polymer powder materials, namely in a pseudo-liquid state, electrostatic, thermojet, gas flame, have become the most widespread in production. Each of the listed methods has its own features and advantages and disadvantages, which determine the scope of their use based on the parameters of the objects to be coated, their structures and features, conditions of future operation, as well as the required thickness of the polymer coating layer. The only factor that unites all methods is the thermal effect in the process of creating a polymer coating, which is necessary for the formation of a strong adhesive bond between the coating and the substrate. The article shows the results of research into the possibility of using a device for gas-dynamic application of metal coatings to create polymer coatings, and its modernization in order to eliminate the identified shortcomings and achieve optimal conditions for the formation of polymer functional coatings. The possibility of a high-speed coating application regime and its influence on the formation of the coating were analyzed. The structure of the researched gas-dynamic device for applying coatings is shown, which contains an electronic heater for the flow of compressed air, and a nozzle assembly for accelerating the heated compressed air in which, due to the ejection effect, the molten polymer material is sucked in and accelerated, which can be in the form of a finely dispersed powder or in the form of a solid dart in the hottest zone with a temperature of about 350 ºС, which contributes to its rapid melting to a liquid state, at the same time, reducing the length of the nozzle to 40 mm allows maintaining the temperature of the polymer material at the level of 230 ºС, which allows the formation of a high-quality coating, while the air pressure is reduced from 0.5 MPa to 0.02 MPa. The conducted studies showed that the use of gas-dynamic sputtering makes it possible to significantly simplify the control and regulation of the heating temperature of polymer materials compared to gas-flame sputtering, due to the possibility of adjusting the temperature of the air flow by changing the current strength on the heating element. Compared to the technology of creating polymer coatings using powder paints, there are also significant advantages associated with the fact that there is no need for long-term heating of these coatings in thermal polymerization chambers. In addition, it is possible to apply polymer coatings on the surface of large-sized products that are not limited by the size of thermal chambers.
The article presents the results of research on the processes of creating conductive coatings based on copper and aluminum in order to determine the interaction of components on each other during cold gas-dynamic spraying (CGDS) and substantiate the method of introducing an additional component to obtain the desired composite coating. In particular, under conditions when the copper sputtering coefficient is almost zero (at a working air temperature of 300 °C), it is the search for the experimental dependence of the sputtering coefficient on the percentage of copper and aluminum powders in the sprayed mixture, determining their residual content in the coating and then calculating based on these data, the sputtering coefficients of copper and aluminum. The CGDS method obtained samples with composite coatings from mixtures of aluminum and copper powders at different initial mass concentrations of aluminum (from 0 to 100%, in increments of 10%) Other things being equal (air pressure 0,6 MPa, air heating temperature 300 ° C) . The spraying ratio of the mixture and the residual content of the components in the obtained composite coatings were measured. Data on the residual content of the components in the coating allows you to select the composition of the source powder required to obtain a given content of components in the coating. The dependences of the sputtering coefficients of copper and aluminum on the mass content of aluminum in the sprayed mixture are found. At an initial concentration of aluminum less than 66%. the coefficient of copper sputtering is higher than the coefficient of sputtering of aluminum. Both increase monotonically with increasing aluminum concentration until it reaches 61%. At high concentrations of aluminum (more than 66%) the spray coefficients of copper, aluminum and their mixtures coincide. The obtained data on the residual content of the components in the coating allows you to select the composition of the source powder required to obtain a given content of components in the coating. For example, the maximum residual copper content (~ 95%) can be obtained by adding to the source powder 30-40% aluminum. The obtained results confirm the interaction of the components on each other and justify the method of introducing an additional component to obtain a composite coating containing a component that is difficult to spray.
The work shows that among the existing sufficiently described and studied approaches that are suitable for analyzing the temporal realization of a vibosignal, which can be obtained during the operation of a real electric machine, one can single out Fourier transforms and discrete wavelet transformations. An analysis of the descriptions of vibro-acoustic signals given in the literature, caused by the asymmetry of the power supply, shows that this defect leads to the appearance of oscillations that contain a harmonic component localized at the frequency of the supply voltage of the electrical network. This fact justifies the expediency of analyzing the frequency range, which includes the frequency of the supply voltage, and the selection of the mother wavelet, based on the features inherent in a single harmonic oscillation. A method for detecting a defect in the asymmetry of power supply to rotating electric machines of alternating current using a discrete wavelet transformation of a vibro-acoustic signal is proposed. The frequency band has been established, which is advisable to analyze in order to identify the indicated defect. It was found that the detection of a power asymmetry defect with the use of the wavelet transform of the temporal realization of the vibroacoustic signal is advisable to carry out using the Haar maternal wavelet function, which provides a combination of a high degree of affinity of the maternal wavelet with the form of vibration change due to the introduced asymmetry and relative the simplicity of such a transformation. It is shown that when detecting power asymmetry, it is advisable to analyze the behavior of the wavelet coefficients of the frequency band, which includes the frequency of the supply voltage of the electric machine. Since the influence of the indicated defect on other frequency bands will be minimal, the analysis of the behavior of their wavelet transform coefficients in order to identify the indicated defect is ineffective. A numerical criterion for assessing the influence of power asymmetry on the wavelet transform coefficients is proposed in the form of the mean square value of the wavelet coefficients of the informative frequency band in the study of the time interval, which significantly exceeds the period of the supply voltage of the electric machine. It is shown that this criterion has a reduced sensitivity to the impact of non-informative single disturbances that may arise during the operation of an electric machine. Keywords: electric machine, rotor unbalance, defect, burst, wavelet transform.
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