The advantages of using frequency converters are well known. First of all, this is a significant energy savings due to the regulation of the rotational speed of the electric motor. In addition, ensuring a smooth frequency start using frequency converters significantly reduces thermal and mechanical loads when starting synchronous motors with a rotor excitation winding and with permanent magnets. In this paper, the start-up of a synchronous motor with a two-link frequency converter for various types of load was investigated. The following issues were considered: - creation of a three-phase two-link frequency converter model for a synchronous drive; - calculation of the torque on the shaft at rated power, as well as coefficients reflecting the nature of the load; - simulation of the start-up and operation of a synchronous motor and a two-link frequency converter with fan, conveyor and constant shaft loads. In conclusion, the model of a two-link frequency converter with a synchronous motor, which was researched in this paper, can be used in systems where the considered types of loads are used. This circuit has high energy characteristics, reliability and stability, and is also able to reduce the amplitude values of currents and time of transient processes at start-up
Keywords: two-link frequency converter, permanent magnet synchronous motor, mathematical model, reliability, PSIM
This paper describes the methods used to take into account the nonlinearity of magnetic processes in the steel of an electric asynchronous machine. This is required for some cases when these physical processes play an important role in the accuracy of data. Justifications are presented that prove the need to approximate the magnetization curve of asynchronous machines to improve the quality of regulation of the electric drive, as well as improve control by energy criteria. Work at full load or near it leads to a decrease in the magnetization EMF due to a voltage drop in the stator, this must be taken into account. The article also shows the approach of applying the methods of accounting for saturation in synchronous machines for asynchronous using transformed equations.
Keywords: induction motor, electricial drive, vector control, saturation curve fitting
Using the concept of the model-based design, this article considers the stages of generating the C-code of the engine control algorithm using the Embedded Coder and STM32 Embedded Target tools for Matlab/Simulink. For the example of the chosen stm32 microcontroller, its peripherals will be initialized and connected to the graphical model of the algorithm. In addition, a description of all the blocks and their functions of the resulting model is provided. At the last stage, the C code is generated, ready for loading it into the microcontroller and further controlling the motor as part of the electric drive.
Keywords: Model-based design, Matlab/Simulink, STM32, the control algorithm, STM32 Embedded Target, Embedded Coder
In this paper, we consider the simulation of a 5.1 kW synchronous electric motor with a two-link frequency converter with a control system that monitors the speed on the shaft in the PSIM simulation environment. IGBT M2TKI-50-12 manufactured by Elektrovypryamitel Saransk were selected for the load current. In this case, the load on the shaft abruptly changed from 1.25 to 2 of the nominal value. Presented are graphs of current, output power, motor speed and torque on the shaft.
Keywords: permanent magnet synchronous motor, PSIM, two-link frequency inverter, spasmodic load variation
This article describes the stages of modeling the state control algorithm for a synchronous motor with permanent magnets using the model-based design method. The algorithm is based on the principle of field oriented I-Hz control, the constructions of which is formed as a state machine for the correct planning of tasks. The model input and output signals for the STM32 microcontroller are further classified. The control model itself is created in the Matlab/Simulink package, the subsystems of which are also described. The last step is to model and visualize the input/output signals of the system at different initial values of the inverter speed and current. By observing acceptable values of the inverter speed and current in the steady state mode, the correct operation of the control logic is ensured, which can be generated as a C code and integrated into the microcontroller.
Keywords: Model-based design, Matlab/Simulink, STM32, synchronous motor with permanent magnets, field-oriented control
This article concentrates on the issues of radio wave propagation in forest conditions. The issue of representing the forest mass as a heterogeneous structure with a low dielectric constant is considered. Calculation and comparison of radio signal attenuation using several empirical models were carried out. It is shown that empirical models take into account the heterogeneous structure of the forest when moving from free space to the forest.
Keywords: radiowave propagation, wooded area, empirical model, radiowave attenuation, path loss, ground mobile communication, electrodynamic characteristics of a heterogeneous structure
The parameters of the porous structure and the active surface of cobalt catalysts for Fischer-Tropsch synthesis (SFT) prepared by the impregnation method have been studied. Characteristics of composition and porous structure were studied using elemental analysis and the Brunauer-Emmett-Taylor method (BET). The effect of the addition of oxide promoters on the specific surface area, pore volume and pore size of the Co / SiO2 catalyst has been studied.
Keywords: Fischer-Tropsch synthesis, heterogeneous catalyst, promoter, carrier, specific surface area, porous structure, selectivity, activity, dipping method
The parameters of the porous structure and the outer surface of cobalt catalysts for the synthesis of Fischer-Tropsch, promoted by magnesium, prepared by the impregnation method according to moisture capacity, were studied. The effect of polymorphic modification (γ, θ, α) of the carrier on the physicochemical properties of the catalyst Co-Mg / Al2O3 was studied.
Keywords: Fischer-Tropsch synthesis, polymorphic modifications of Al2O3, synthetic motor fuel, catalyst, carrier, elemental analysis, BET method, specific surface, porous structure
Three batches of Co-MxOy / SiO2 catalysts were prepared with different methods of introducing an oxide additive. Physicochemical studies of catalysts by elemental analysis and Brunauer-Emmett-Taylor (BET) methods have been carried out. The effect of additives of oxide promoters and the method of their introduction on the specific surface, volume and pore sizes for Fischer-Tropsch synthesis catalysts were studied.
Keywords: Fischer-Tropsch synthesis, carbon-containing resources, catalyst, active component, silicate carrier, Al2O3 and ZrO2 promoters, elemental analysis, BET method, surface area, volume and pore size
The article analyzes the natural conditions of the Northern latitudes of Russia, where the main reserves of fossil hydrocarbons and metals are concentrated. It is shown that mining requires the development of the road network and artificial structures on the roads. It is noted that the most difficult stage in the construction of bridge structures is the construction of foundations. The types used in the Northern latitudes of foundations are considered, and their positive and negative qualities, such as weight, method of construction and volume of earthworks, are noted. The paper emphasizes the relevance of the problem of maintaining the stability of permafrost soils in seasonal thawing and loss of their bearing capacity. Methods of maintaining the soil in a solid state can be natural and artificial. The methods of thermal stabilization of soils, as well as machinery and equipment used in these conditions.
Keywords: permafrost, road network, bridge, polystyrene, superstructure, pile support, Foundation, thermal insulation screen, heat stabilizer
The dispersion parameters of the active component of cobalt catalysts promoted by nickel for Fischer-Tropsch synthesis by the temperature-programmed hydrogen desorption method (TPD H2) were studied. The influence of the polymorph (γ, θ, α) of the support on the physicochemical properties of the Co-Ni / Al2O3 catalyst was studied.
Keywords: Fischer-Tropsch synthesis, biomass, catalyst, support, Ni promoter, polymorphic Al2O3 modifications, TPD H2 method, active surface, dispersity, cobalt crystallites
This article is dedicated to one of the symbols of Volgograd city, which is the Astrakhanskiy Bridge. We described the history of creation and the technical specifications of the bridge over the Tsaritsa river. After conducting an investigation, some defects in the bridge construction were uncovered. The framework arcs have longitudinal cracks, the protective layer of concrete is destroyed; the longitudinal main reinforcement is exposed and corroded. The protective layer of concrete was removed and the longitudinal main reinforcement was corroded on the longitudinal beams. During operation of the bridge, the defects that decrease load capacity and durability appeared: destruction of the protective layer of concrete on a plate of about 2 square meters. This led to the beginning of corrosion of the lower reinforcement net. Steel brackets, holding the walkway slabs, are heavily corroded; the protective paint coating on them is destroyed over significant lengths. The analysis of detected damage allowed to evaluate their impact on the durability and load capacity of the construction and determine those, who are responsible for its occurrence. It is noted that postponing of repair operations has a negative impact on the state of the bridge.
Keywords: bridge, city symbol, superstructure, roadway plate, defects, arch, bridge system, bearing structures, durability, load capacity
The article presents calculation of the cost of overlappings from LSTK and wooden ones. The floors of the two-storey house with a span and overlap with a span of 12 m were calculated. Calculation of the cost of materials is presented for each option. In conclusion, conclusions were drawn on the rational use of material types for each of the calculated spans.
Keywords: light steel thin-walled structures, LSTK ceiling, wooden flooring, reduced characteristics, effective cross-section, construction
The lack of standards for the calculation of lightweight thin-walled steel structures allowed low-quality producers to save on production, which endangered the people who exploited such buildings. The appearance of normative documents for the calculation of thin-walled structures entails responsibility for the affirmers of these normative documents. In Russia, such norms appeared relatively recently and the purpose of this study was to compare domestic normative methods of calculation with non-significant ones. During the presentation of the study, the concept of a reduced (effective) section of a beam when working on bending was considered. Also, the same stages of the calculation methods were noted, indicating the places where the methods differ in their opinions. The result of this study is a comparison table for the basic geometric characteristic for obtaining the bearing capacity of an effective torque element of resistance. An analysis was carried out and a conclusion was drawn on these values.
Keywords: steel structures, light steel thin-walled structures, thin-walled beams, reduced cross-section, bending work, C-shaped profile, effective cross-section, effective area, effective resistance moment
In this paper, it is proposed to update the values of the bearing capacity of the hinge attachment of the beams to the columns on 2 bolts. A comparative analysis of the bearing capacity of the assembly presented in the 2.440-2 release 1 series and calculated according to modern building codes is carried out. Five calculation formulas were obtained for the five possible limiting states of the node. A table with the values of the limiting forces perceived by the connection is presented. A possible variant of improving the assembly is presented, by including a support table in the work.
Keywords: bearing capacity, metal structures, hinged unit, structural solution, connection of elements, limit state