Showing papers in "Russian Electrical Engineering in 2018"
TL;DR: Analysis of statistical data revealed that the most likely cause of incorrect triggering of relay automation is atmospheric phenomena—lightnings and ensuing overvoltage and it is most appropriate to carry out fault diagostics using the half-interval method taking into account the possibility of no-failure operation.
Abstract: The main reasons for false (incorrect) triggering of microprocessor relay-protection systems are analyzed. Methods of increasing the reliability indicators of relay-automated systems are considered. Analysis of statistical data revealed that the probability of no-failure operation of microprocessor relay-protection systems is no lower than 0.998. Increasing the reliability indicators of microprocessor-protection systems does not require a revision of the Electrical Installation Rules, but requires using high-quality cable products with normalized technical characteristics and transition to a digital data-transfer format with a limited number of variables transmitted by one serial channel. The approximate upper and lower bounds of dependence of the cost of improving the reliability of microprocessor system are stated. For example, halving the amount of failures requires increasing the capital costs for electromagnetic protection by three to four times. Maintenance of the level of reliability of microprocessor system during operation is possible only during implementation of routine measures of evaluating the electromagnetic environment. Statistical data showed that the most likely cause of incorrect triggering of relay automation is atmospheric phenomena—lightnings and ensuing overvoltage. Therefore, at the stage of determination of the electromagnetic state, it is necessary to note the state of the earthing system it is most appropriate to carry out fault diagostics using the half-interval method taking into account the possibility of no-failure operation.
40 citations
TL;DR: In this article, an analysis of independent control actions in different control structures is performed to compare different methods for improving the specific mass and dimensions of electric drives for objects that carry out point-to-point motion or tracking motion.
Abstract: An analysis of independent control actions in different control structures is performed to compare different methods for improving the specific mass and dimensions of electric drives for objects that carry out point-to-point motion or tracking motion. Algorithms for optimizing the form of phase (control) currents are formulated. The physical modeling method has shown that a rectangular oscillogram of the phase current in a series excitation circuit is most convenient for use in overload zones. It is shown that improved mass and dimensions in the low-power range can be achieved in synchronous reluctance electric drives having a complex rotor design (compound design with nonmagnetically conductive inserts). A multiphase circuit with individual sources in each phase is an appropriate circuit for use in high-power electric drives (more than 500 kW). Improved acceleration performance is achieved without complicating the design of the rotor due to the failure of sinusoidal control laws. In this case, the parameters of the electric drive under consideration are comparable with the parameters of a synchronous reluctance electric drive having a compound (complex) rotor. The form of the phase current is rectangular at the initial stage of adjustment, and the ratio between the excitation current and the armature current is determined depending on the saturation coefficient of the magnetic system.
33 citations
TL;DR: A determination of the possibilities of design procedures depending on the number of processors and the nature of the problem to be solved is presented and it is shown that, if an electric drive has small overloads and they are in the tolerance zone, then it is more appropriate to give a preference to simplified design models.
Abstract: The design procedure for electric drives operating in a zone of large overloads or having the motor with unconventional rotor design is presented. The calculation of the magnetic system is based on the finite-element method. In addition, the settings for the phase currents come from the control system. To reduce the time of calculation, an algorithm for parallelizing the calculations by the criterion of maximum acceleration was developed. A determination of the possibilities of design procedures depending on the number of processors and the nature of the problem to be solved is presented. It is shown that, if an electric drive has small overloads and they are in the tolerance zone, then it is more appropriate to give a preference to simplified design models and the parameters of an electric machine can be replaced by lumped ones. If an asynchronous electric drive operates with larger overloads (with an impact character of the torque of resistance or when frequent starting-brake operating modes with relatively large dynamic torque), it is appropriate to use refined design procedures. Electric drives with a complicated configuration of the magnetic system—for example, drives with a synchronous reluctance machine—require taking the distributed nature of the motor magnetic system into account. Moreover, there are electric-drive operating modes in the zone of large overloads by torque and with angles β < 30°, when higher demands are placed on the initial data of the design model.
33 citations
TL;DR: It is determined that, in addition to the known advantages of such a circuit, it is possible to increase additionally the coefficient of efficiency of a frequency converter due to a larger number of the degrees of freedom during the switch over to multiphase circuits.
Abstract: This paper presents a method for improving energy indicators and increasing system reliability by adopting multilevel schemes of power circuits of semiconducting frequency converters of a voltage class of up to 1 kV. An optimum number of phases was selected at the first stage based on the criterion of the minimum cost to solve the problem. Then, this criterion was supplemented by the limitation of the electric losses and, at the final stage, the problem was solved based on the condition of securing the specified indicator of the failure- free operation. Modern semiconducting converters for the large specified capacities are of modular configuration and each of the frequency converter assemblies (rectifier, invertor) includes, as a rule, some parallel connected modules. In these conditions, an increase in the number of phases at which the phase winding of the engine is made multiphase and the previously parallel-connected power modules of self-commutated inverters are galvanically decoupled and connected separately to each of the engine phases, which allows increasing the reliability indicators of the system without any additional capital costs. It is theoretically shown and experimentally confirmed that, due to the development of the modern element base, the use of three-level frequency converters for a voltage up to 1 kV is economically justified. It is determined that, in addition to the known advantages of such a circuit (reduction in the switching losses and overvoltages on the phase winding of the engine), it is possible to increase additionally the coefficient of efficiency of a frequency converter due to a larger number of the degrees of freedom during the switch over to multiphase circuits.
33 citations
TL;DR: It has been demonstrated that the best effect is achieved at the second stage due to application of elongated motor, and it is possible to decrease inertia by about two times and the total transient time by about 25–30%.
Abstract: This article discusses selection of variables of electrical power equipment and variables of adjusting feedbacks of a control system of heavy-duty equipment using sequential partial optimization. The stages of the proposed procedure as well as its evaluation are exemplified by electric drive of cold rolling mill. It has been demonstrated that the best effect is achieved at the second stage due to application of elongated motor; herewith, it is possible to decrease inertia by about two times and the total transient time by about 25–30%. Practical design methods of electrical-power equipment of high precision drives can be supplemented by certain stages. This is very important for equipment operating in wide range of loads on the working shaft (more than four to five rated values) and/or that contains elements with mechanical compliance in control channel. By means of appropriate selection of the reduction ratio, it is possible to decrease significantly the influence of resonant maximums, which is necessary if the mechanical part is to meet requirements for quality of adjustment of a sequential correcting device of a conventional subordinate process-control circuit of a metallurgical electric device. The proposed procedure can be successfully applied also in systems with conventional variables for mechanisms operating with frequent starts/brakes. For instance, getting rid of ratios of rotor length to its diameter that are conventional for an asynchronous motor in some cases permits losses to be approximately halved.
32 citations
TL;DR: In this article, a detailed magnetic equivalent circuit of a linear-induction-motor longitudinal section with the introduction of the Bolton coefficient was proposed to correct for the transverse-edge effect in a solid secondary element.
Abstract: Electric drives based on traction linear-induction motors are used in industry and city transport. The main advantages of this electric drive are unrestricted acceleration and vehicle climbing angles, as well as ecological cleanliness. The development of high-speed design and analysis software tools for linear electric motors is thus becoming quite timely. The use of the finite-element method for solving field problems in a three-dimensional setting and dynamic vehicle-operation regimes is time-consuming. It is proposed to use a detailed magnetic equivalent circuit of a linear-induction-motor longitudinal section with the introduction of the Bolton coefficient to correct for the transverse-edge effect in a solid secondary element. Model features based on multilayer magnetic equivalent circuits are shown, and the effect of the number of layers on the designed motor-traction force is evaluated. When selecting an appropriate pole pitch-to motor gap ratio, a two-level equivalent circuit turns out to be suitable. The secondary element is represented in the model as a set of rectangular rods connected in parallel. The influence of the calculation method of the secondary rods’ motional EMF on the motor-traction-force accuracy is shown. The greatest error is observed in a low-slip region (when the motor passes into a generative braking regime) and the simplest spatial derivative of the magnetic flux. When the derivative calculation formula becomes more complicated, the indicated error sharply decreases. Another way to reduce the calculation error of the motional EMF in the secondary element circuit is to increase the number of these circuits by decreasing the width of the elementary rod. The prominence of the detailed magnetic equivalent-circuit method and convenience of online viewing should be noted.
20 citations
TL;DR: The algorithm for control-action optimization proposed in this work enables one to increase the energy efficiency of synchronous reluctance and inductor ac electric drives.
Abstract: An algorithm for optimizing the control action in the torque contours of synchronous reluctance and inductor ac drives is described in this paper. It allows one to search for an optimal principle for electric-drive operation that is suitable for any electromechanical converter with magnetic asymmetry of the rotor. The harmonic composition of phase currents serves as the optimization parameter. The optimization criteria are specific electric and magnetic losses. The functional relations presented by a set of equations describing the mathematical model of an object for optimization are given in analytical and numerical forms. The analytical case implies the optimization calculations at the following assumption: the drive is unsaturated, the magnetic conductivity of steel is infinite, and there are no scattering currents. The optimization data are to be refined via the numerical method, in which the electric drive is to be as a system with distributed parameters. An example of synthesis of the best configuration of phase currents through the torque contour of an electric drive with a synchronous independent-excitation reluctance machine is considered as well. The optimum current shape is established to be a trapezoid, while the time of the control signal variation is determined by the time after which the rotor-pole edge overcomes a distance equal to a phase area of the stator winding. The algorithm for control-action optimization proposed in this work enables one to increase the energy efficiency of synchronous reluctance and inductor ac electric drives.
17 citations
TL;DR: In this paper, the authors describe electromagnetic fields and noise for physical simulation of the effect of high-voltage power lines on the impact of electromagnetic interference in the electronic mains.
Abstract: High-voltage transmission lines are powerful industrial sources of electromagnetic noise in electronic mains Mathematical models describing electromagnetic fields and noise for physical simulation of the effect of high-voltage power lines are developed The mathematical models, a scheme of the experimental test bench, equipment, and calculated parameters of physical models are the basis of practical methods in physical simulation of electromagnetic interference in electronic mains upon the impact of high-voltage power lines Examples of implementation of physical simulation of electromagnetic interference confirm the practical suitability of this approach and rather high accuracy of studies (the deviations do not exceed 30%)
12 citations
TL;DR: In this paper, the authors studied the working intensity of the electrical field in the cast epoxy insulation of a 6- to 110-kV switchgear taking into account its dimensions, structure, and basic operational factors.
Abstract: The method of choice of the working intensity of the electrical field in the cast epoxy insulation of a 6- to 110-kV switchgear taking into account its dimensions, structure, and basic operational factors is studied The volt–time characteristics of the electrical strength of the cast epoxy insulation corresponding to a low probability of the breakdown at the different intensity of the partial discharges are analyzed It is shown that the distribution of the electrical strength of the cast insulation under the short-term and long-term action of the commercial-frequency voltage is well described by the Weibull law and the influence of the dimensions on the electrical strength is specified by the “active” volume of the dielectric—the area where the electricalfield intensity makes up no less than 85% of the maximum in the clearance The estimation of the permissible field intensities in the cast insulation of a 10- to 35-kV switchgear with various degrees of the field inhomogeneity and intensities of the partial discharges is given
10 citations
TL;DR: In this article, the main characteristics of electromechanical, inductive, capacitive, and electrochemical energy storages are considered from the point of view of effectiveness of their use as onboard energy storage in traction rolling stock.
Abstract: The important problem of increasing the energy effectiveness of traction rolling stock of railways and urban electric transport can be solved using onboard energy storages in traction electric drive systems. Onboard energy storages can perform a number of important functions promoting the efficient use of energy resources: storage of energy during cessation of electric braking, equalization of the schedule of power consumption from the prime heat engine, and storage of excess energy of regenerative braking. The main characteristics of electromechanical, inductive, capacitive, and electrochemical energy storages are considered from the point of view of effectiveness of their use as onboard energy storages in traction rolling stock.
10 citations
TL;DR: In this article, the authors considered the processes of energy exchange in traction drive systems with onboard capacitive energy storages during acceleration and electric braking of rolling stock, and the energy exchange processes were considered in relation to resistive charging and discharging circuits and circuits with reactors.
Abstract: Regenerative braking with return of energy to an aerial contact wire in principle makes it possible to reduce the energy consumption for traction needs, but in real conditions the effectiveness of this braking type as a means of reducing the consumption of energy resources is often limited. The electric braking of rolling stock is more effective and independent of the external conditions in which the generated energy is stored in onboard energy storages. The largest reduction of consumption of energy resources for traction needs when using onboard energy storages composed of traction the electric drives can be achieved for rolling stock operating with frequent starts and stops. These types of rolling stock include suburban electric trains, subway trains, and urban electric transport, to the specific operation of which capacitive energy storages based on supercapacitors correspond best. This work considers the processes of energy exchange in traction drive systems with onboard capacitive energy storages during acceleration and electric braking of rolling stock. The energy exchange processes are considered in relation to resistive charging–discharging circuits and circuits with reactors, and the main attention is devoted to the effectiveness of energy exchange processes. The energy consumer in an energy-storage discharging circuit and the source of energy in the charging circuit are represented by an EMF source, which in general can change with time. The dependences of energy effectiveness of charging and discharging processes of capacitive energy storage on its initial voltage and on the rate of change in the EMF of energy consumer are obtained.
TL;DR: In this article, a method of control of the metal-transfer mode during electron-beam surfacing with a filler-wire feed based on simultaneous recording of the potential of the wire and article connected with the apparatus frame through the resistors is presented.
Abstract: This paper presents a method of control of the metal-transfer mode during electron-beam surfacing with a filler-wire feed based on simultaneous recording of the potential of the wire and article connected with the apparatus frame through the resistors. The main metal-transfer modes are specified that are observed with a change of the energy-input rate. The importance of the solved problem for additive technologies is shown. A scheme of experimental investigations carried out at the ELA-15I apparatus is given, and the obtained oscillograms are presented. The relation of the characteristics of the registered signals with the operation modes of the equipment and transfer parameters is shown. It is noted that, with a change of only the filler-wire feed rate, a changeover from drop metal transfer to the scattering mode can be triggered. The possibility of detecting the mode of appearance of the shot metal, as well as emergency modes related with stopping the filler-wire feed or excessive increase of its feed rate, is substantiated. The influence of the plasma processes on the registered signals in the developed scheme is analyzed, and it is also shown that, to reduce the influence of these processes, it is necessary to decrease the resistance of the measuring circuit. Photographs of the process corresponding to the certain oscillogram intervals are given.
TL;DR: New technical solutions and calculation methods for unconventional energy-saving machines with improved mass and volume performances are presented.
Abstract: In modern power setups of autonomous objects, electromechanical converters with good mass and volume performances are used. However, the problem of lowering the specific energy parameters of electric machines remains important. This article presents new technical solutions and calculation methods for unconventional energy-saving machines with improved mass and volume performances. The electromagnetic core of machines includes a stator winding with active and front conductors of rectangular cross section. The cross section of the jumpers for connections of active and front conductors is reduced. The front conductors of the stator winding do not intersect. These measures make it possible to reduce the consumption of copper, achieving a decrease of the length of the electromagnetic core while maintaining high efficiency. It has been shown that manufacturing such multilayer wavelike windings is promising. The design of the an induction motor with a stator winding of this type has been considered. The technical features in designing electrical machines with a new stator winding are discussed. A detailed end-face scheme of the stator winding and a scheme of the sequence of conductor commutation of this winding are presented. Expressions for calculating the overhang parts of the winding are given. Results of comparison new and serial motors with a power of 75 kW are given.
TL;DR: The main ways in which modernization is carried out of drilling-vessel electric- energy systems are to ensure the operation of the vessel power plants on a common bus without reducing the reliability of the power supply of the positioning system and realizing the idea of the split power islands in the electric-energy system.
Abstract: This article considers the characteristic features of the electric-energy systems of the dynamicpositioning drilling vessels Stena Drillmax of Samsung Heavy Industry dockyard, Discoverer Clear Leader of DSME-DAEWOO shipbuilding and Marine Engineering dockyard, and Pacific Scirocco of Maersk Viking dockyard. The electric-energy systems of the drilling vessels include four to eight generator sets connected to the main electric switchboards located in isolated machine compartments separated from each other by watertight and fire-resistant bulkheads to increase the survivability. The propulsion system includes, as a rule, six azimuth thrusters with semiconductor frequency converters. The main ways in which modernization is carried out of drilling-vessel electric-energy systems are to ensure the operation of the vessel power plants on a common bus without reducing the reliability of the power supply of the positioning system and realizing the idea of the split power islands in the electric-energy system using a modernized monitoring and protection system for diesel generators (AGS, AGP blocks), a system of electrical distribution, and a more efficient algorithm of functioning of the PMS automation system, which in the case of the accident allows localizing the emergency area within one main switchboard without deenergization.
TL;DR: A new method of identifying unmeasured currents flowing into the interpersonal sections of a DEN, which takes into account the effect of specific disturbing factors and does not require information concerning these resistances.
Abstract: This paper considers the lower level of a power system—a distributing electrical network (DEN) with a voltage of 0.4 kV that produces suppliable electricity as a marketable product. The creation and introduction of modem automated systems of control and accounting of electricity (ASCAE) raises an important problem of monitoring of nonnormative losses of electricity in the DEN and identification its unmeasured (uncontrollable) electric parameters in the presence of distributing factors, such as unsanctioned selection of electricity and leakage currents in the network. The application for this purpose of existing methods and algorithms in real time presents certain difficulties because of the stochastic character of individual DEN parameters, for example, the active resistances of interpersonal sections that changes depending on external factors (temperature, humidity, etc.). The paper presents a new method of identifying unmeasured currents flowing into the interpersonal sections of a DEN, which takes into account the effect of specific disturbing factors and does not require information concerning these resistances. The method can be used to create special software subsystems of an ASCAE intended for identification of common and nonnormative electricity losses and also to localize the coordinates of unsanctioned selection of electricity and leakage currents in the network.
TL;DR: In this article, an induction-type linear-pulse electromechanical converter with an external magnetic, electromagnetic, or combined magnetic-electromagnetic shield has been considered, and it has been shown that the efficiency of a converter with a combined shield is two to three times higher than that when using a magnetic or electromagnetic shield of the same dimensions.
Abstract: An induction-type linear-pulse electromechanical converter with an external magnetic, electromagnetic, or combined magnetic–electromagnetic shield has been considered. A mathematical model of a converter, which takes into account rapid interconnected electromagnetic, thermal, and mechanical processes, has been developed using the finite-element method. The effect of the geometrical parameters of a shield on the converter performance has been considered. A criterion of efficiency that takes into account the relative values of the efficiency, mass, and stray field of a converter has been introduced. It has been shown that the efficiency of a converter with a combined shield is two to three times higher than that when using a magnetic or electromagnetic shield of the same dimensions.
TL;DR: A review has been carried out of methods for increasing the energy efficiency of automatic control over the movement of subway trains: choosing an energy optimal sequence of train control modes, distributing the travel time along the line for travel times over the sections between stations, and using the regenerative braking mode.
Abstract: A review has been carried out of methods for increasing the energy efficiency of automatic control over the movement of subway trains: choosing an energy optimal sequence of train control modes, distributing the travel time along the line for travel times over the sections between stations, and using the regenerative braking mode. The results of a study related to the influence of the automatic control system on the energy consumption for traction by train are presented. An analysis of the effect of the increase in the time of impact braking in conditions of different types of sections between stations on additional energy consumption at a given train travel time over the section between stations both in the absence and in the presence of a regenerative brake was carried out. The requirements for the path correction sensors, which should provide the necessary accuracy of the train positioning during intense braking, are formulated. A comparison of corrective sensors based on infrared signals and RFID sensors is made. The effect of changing the travel time on the section between stations in order to compensate for the discrepancy between the planned and executed traffic graphs for additional energy consumption was analyzed. In conditions of intense traffic, the requirements for the permissible error in the execution of a given train travel time over the range are ±2.5 s.
TL;DR: Two blocks were commissioned of an RZhFA-6500 reactor as part of the two-link smoothing device at the Letnaya traction substation of the Sverdlovsk Railroad and analysis confirmed the efficiency of the new type of reactor in the structure of a two- link filter device.
Abstract: Two blocks were commissioned of an RZhFA-6500 reactor as part of the two-link smoothing device at the Letnaya traction substation of the Sverdlovsk Railroad. To test the efficiency of the reactor, a forced short circuit experiment was performed without stopping the movement of the electric vehicle over the section, the level of psophometric voltage on the dc buses of the traction substation was measured and an experiment was carried out of a forced short circuit with cessation of movement over the section. During the experiments, oscillograms of transient processes were taken, analysis of which confirmed the efficiency of the new type of reactor in the structure of a two-link filter device.
TL;DR: In this article, the authors measured the resistance of rail threads within the rail circuits and found the elements, the resistances of which go beyond the limits of the norm, due to an asymmetric increase in the transient electrical resistances in the joints of rail links and in the choke bridges.
Abstract: Up to half of failures in the operation of rail circuits and automatic locomotive signaling at the sections of railways with ac electric traction occurs due to the disturbances caused by the traction current asymmetry in the rail lines. Since the primary source of this asymmetry is the asymmetry of resistances of rail threads within the rail circuits, the measurements of the resistance of elements of each rail thread make it possible to not only define the traction current asymmetry, but also to find the elements, the resistances of which go beyond the limits of the norm. The traction current asymmetry can also be measured directly; however, the measurement results depend as well on the conditions of their being carried out—on the temperature of rails and the magnitude of alternating traction current in them. This is explained by the fact that the asymmetry of resistances of rail threads of rail line is formed owing to an asymmetric increase in them in the transient electrical resistances in the joints of rail links and in the choke bridges. These transient resistances depend on ambient temperature and traction currents in rail threads slightly. As a result, when decreasing the temperature of the rails of P65 type from +40 to –40°C, the asymmetry of resistances of rail threads taking into account their mutual inductance increases by 2.2—2.4 times, while increasing the traction current in rails, for example, by three times causes almost the same asymmetry increase. The influence of mutual inductance of rail threads with the contact wire leads to a decrease in the traction current asymmetry in the rail line. The mutual inductance of rail threads with high-voltage lines of longitudinal power supply that are placed on the contact line supports can increase or decrease this asymmetry, depending on which of the rail threads has less resistance. All these factors should be taken into account both when measuring the asymmetry of resistances of rail threads or the asymmetry of alternating traction current in them and when extrapolating these data to other operating conditions of the rail traction network by the rail temperature or by the magnitude of currents in rail threads, contact wires, and high-voltage lines.
TL;DR: A calculating algorithm for the power factor is proposed in this work, which takes into account the influence of distortion power.
Abstract: The high harmonics of voltage and current that are generated by traction transformers mounted on ac electric rolling stock have a negative influence on systems of electrical power distribution and their components. The exact interrelation between harmonics and losses is too complicated to generalize, and, therefore, the influence of the form of current and voltage is determined as a rule using the power factor. The fundamental disadvantage of ac electric locomotives is a low power factor. To improving energy indices, methods were developed that make it possible to increase the power factor. The effectiveness of the proposed methods as a rule is estimated by means of determining the power factor. A calculating algorithm for the power factor is proposed in this work, which takes into account the influence of distortion power.
TL;DR: In this paper, the results of the theoretical and experimental studies of force interactions between permanent magnets and volumetric high-temperature superconductors (HTCs) are presented.
Abstract: The paper presents the results of the theoretical and experimental studies of force interactions between permanent magnets and volumetric high-temperature superconductors (HTCs). The obtained data are of interest for the design of various devices with HTC elements: magnetic bearings, transport systems with magnetic levitation, electric machines, etc. Numerical analysis of the electromagnetic field was performed by the method of spatial integral equations for the field sources. The properties of the HTC materials and YBaCuO ceramics are represented by a traditional model for transport currents and a combined model that considers the types of field sources inside the superconductor—the transport current density and the related currents (magnetization). For the transport current density, a modification of the critical state model is applied. In this model, the specific electric resistance of the superconductor is presented by a hyperbolic function of the following three parameters: absolute temperature, magnetic field strength, and current density. The model for magnetization is based on the definition of the related currents in the form of the density of the magnetic moments’ combination of the small superconducting cylinders throughout the sample of a high-temperature superconductor. Experimental studies were performed on a specially designed installations with the HТС cryostatting system in a liquid-nitrogen atmosphere and equipment for precision force sensing. Comparison of the experimental results and calculation data confirms the reliability of the developed modeling methods.
TL;DR: In this article, the conductivity of air gaps between the ferromagnetic elements of a magnetic system can be described by a modified method of probable paths of magnetic flux, and the resistance of the elements (magnetic potential drop) is taken into account by means of a mathematically expressed magnetization curve (for steel of 10895 grade).
Abstract: Circuit breakers are one of the most widespread electrical devices in control and distribution systems that use electric energy fluxes, providing protection from short circuits and current overloads. First and foremost, circuit breakers should provide a high operation speed at shutdown, which can be achieved with low weight and significant electromagnetic forces. For approximate determination of magnetic system dimensions, network analysis methods are used. In addition, the model of magnetic field structure can be substantially simplified. The conductivity of air gaps between the ferromagnetic elements of a magnetic system can be described by a modified method of probable paths of magnetic flux, and the resistance of ferromagnetic elements (magnetic potential drop) is taken into account by means of a mathematically expressed magnetization curve (for steel of 10895 grade).
TL;DR: The proposed hybrid algorithm of arranging reactive power compensation units makes it possible to reduce the losses of electric power in the mains, reduce the voltage deviation, and increase the line power factor.
Abstract: Distribution networks are the direct end-consumer connection part of an electric power system. With the development of technology, advent of new current-using equipment, and increasing population density, these networks are becoming increasingly more and more complex, elements more loaded, and power and voltage losses on the line more significant, which leads to violations of standard requirements. These problems are considered using the example of a section of the Moscow oblast network. The study presented in this article is part of the research project aimed to improve the quality of electric power in the distribution network by analyzing the current state and elaborating corrective steps. The measurements were taken using electric power quality analyzers at maximal and minimal loads. To overcome a high negative voltage deviation, the reactive power compensation unit is proposed. The procedure proposed in this article to solve the given problem consists of two phases. In phase one, loss sensitivity factors (LSFs) are defined and candidate nodes selected for installing the compensation units. This makes it possible to considerably reduce the area of searching for the optimization algorithm and, therefore, cut down the calculation time and improve the algorithm’s convergence. In phase two, the hybrid particle swarm technique is applied to optimally arrange the compensation units among the selected nodes, and choose their capacity. The hybrid optimization technique includes the particle swarm technique (PST) and the quasi-Newtonian algorithm applied after meeting the PST stopping criterion. The quasi-Newtonian algorithm is applied to cut down the time for executing iterations and making the PST more convergent. Numerical modelling is performed in the MATLAB software environment. The measurements in the distribution network of the Moscow oblast served to construct a design model with 111 nodes. According to the measurement results, the voltage level in the consumer coupling nodes considerably overrides the limits defined by GOST (State Standard) 32144–2013. Serious problems with electric power in the mains are connected with inadmissible values of established voltage deviation. The proposed hybrid algorithm of arranging reactive power compensation units makes it possible to reduce the losses of electric power in the mains, reduce the voltage deviation, and increase the line power factor.
TL;DR: In this paper, the results of an investigation of an asynchronous motor in the modes of direct starting and load changing were obtained with mathematical modeling using a block of nonlinear systems of Lookup Table type and functional block Fcn of the MATLAB/Simulink software package.
Abstract: The results of an investigation of an asynchronous motor in the modes of direct starting and load changing obtained with mathematical modeling using a block of nonlinear systems of Lookup Table type and functional block Fcn of the MATLAB/Simulink software package. Introducing the above-mentioned elements into the model makes it possible to simply take into account changes in the parameters of an electrical machine caused by saturation of the magnetic circuit and the effect of current displacement in the rotor bars in transient modes. The saturation of the magnetic system when passing the main magnetic flux and leakage fluxes is taken into account using functional dependences, which are specified in the blocks by tabular methods, which provides model simplicity and clarity of the modeling process. Unlike a model created based on a standard block of an electric motor of Asynchronous Machine type, the proposed variant makes it possible to observe the changes of any variables of asynchronous machine during the transition process and creates good preconditions for various investigations of electric drives. Using the developed model. the comparative analysis was done of dynamic characteristics, which revealed that the transient processes in the asynchronous motor under direct starting, taking into account the saturation of the magnetic circuit and the effect of current displacement in the rotor flow that is 1.5 times faster than in the ideal machine. In addition, the first maximum of torque is 1.6 times greater than in a simplified motor model. Under a load surge, the differences in the curves of changes of torques and angular velocities are insignificant. If to neglect the effect of current displacement in the rotor bars, the transient processes do not coincide only when starting. The most essential differences are observed between the transient characteristics of the developed model and the model composed of the standard MATLAB Simulink blocks. The obtained results make it possible to draw a conclusion as to the effectiveness of applying the developed motor model when investigation of dynamical modes, selecting a starting and protective equipment of asynchronous electric drives.
TL;DR: In this article, the energy relations in a traction ac power supply system including a power multifunctional booster transformer with a nonsinusoidal current and voltage at the current collector of electric rolling stock are considered.
Abstract: The energy relations in a traction ac power supply system including a power multifunctional booster transformer with a nonsinusoidal current and voltage at the current collector of electric rolling stock are considered. The expediency of the selection and regulation of the compensating unit connected to the compensating winding of the transformer based on the minimum exchange energy determined by the presence of the capacity and inductive energy storages is shown. Generating the reactive energy, the booster transformer reduces the voltage losses in the power supply system due to decreasing the primary current. In addition, due to the effects of the bootstrap and series capacity, it exceeds the voltage in the traction network and, therefore, increases the voltage at the current collector of the electric rolling stock. The proposed coefficient of efficiency of the compensating unit allows selecting its capacity with a sufficient accuracy to ensure the optimal operation mode of the traction power supply system, which is on average 15–20% less than the capacity determined using the existing method.
TL;DR: In this article, the authors present a full-scale analysis of analog processes in the electric traction network, discrete signals of automatic controls and telemechanics, and states and switches of cross-connect equipment, which must facilitate increased automation of the traction substation and make it completely unattended.
Abstract: Traction dc power supply systems with a traditional feed voltage of 825 V are part of the basic transport infrastructure of metropolitan cities. The development of electrified railroads has resulted in the mainstream use of these systems. There are many works about their strengths and weaknesses; however, modern circumstances make it necessary to operate and upgrade these systems, maintain their usability, and improve their efficiency. New rolling stock with asynchronous engines is being launched for subway service with increased loads and travel speeds. In these conditions, one of the main features of maintaining the course of transportation is to guarantee uninterrupted power supply of electric rolling stock. This can be made possible through appropriate and timely responses by maintenance personnel, power dispatchers, automation and emergency control systems. The microprocessor systems used at the modern level of technological development have been embodied in intelligent terminals of feeder lines of electric traction networks used in subway service. Their algorithmic part must be improved and upgraded for compliance with the current realities of subway service by integrating emergency control equipment algorithms, full-scale analysis of analog processes in the electric traction network, discrete signals of automatic controls and telemechanics, and states and switches of cross-connect equipment, which must facilitate increased automation of the traction substation and make it completely unattended.
TL;DR: A method of automation of adjustment of the selective characteristic of a locomotive traction generator that makes it possible to use most completely and efficiently the free capacity of the engine.
Abstract: This paper studies a method of automation of adjustment of the selective characteristic of a locomotive traction generator that makes it possible to use most completely and efficiently the free capacity of the engine. The problem of minimization of the functions of several variables is solved using the Hooke–Jeeves method, the algorithm being a combination of the exploratory search with the alternative change of the variables and accelerating pattern matching search in the direction determined in the process of the exploratory search. A computer program is developed allowing automating the process of adjustment of the selective characteristic of the locomotive traction generator. Based on the proposed method, a series of the training programs is developed for studying the electrical circuits of the locomotives. The main difference of these programs from programs of similar purpose is the presence of a detailed mathematical model of the studied circuit node, in which the total functionally of the program is based. This model allows calculating and reflecting the state of the electrical circuit at any state of the control elements and in any operation mode of the power plant using virtual measuring devices for troubleshooting and adjusting the circuit.
TL;DR: This article presents a design of the starter generator with an external rotor for integration with a high-pressure aircraft-engine shaft that has minimal weight–size parameters and high energy performance and works with minimal losses.
Abstract: The notion of a more electric airplane figures strongly in the design of new aircraft. The task that has to be done is to integrate an electric machine directly with a high- and/or low-pressure aircraft-engine shaft. As a result, it is possible to reduce the engine’s weight–size parameters, attain better reliability and fuel saving, and cut down aircraft maintenance costs. To realize this, it is necessary to design a highly efficient high-temperature starter generator able to work in harmful environmental temperatures with minimal technological possibilities for cooling. This article presents a design of the starter generator with an external rotor for integration with a high-pressure aircraft-engine shaft. To attain better parameters and characteristics of the proposed design, optimization by multiple criteria in the Ansys Maxwell software package is conducted. The optimal dimensions of the SG with an external rotor are determined by genetic algorithms. The optimized starter generator has minimal weight–size parameters and high energy performance and works with minimal losses. The operability of the starter generator is assessed by computer modeling on the basis of which a test mockup is designed. The tests are conducted in no-load and loaded modes. The test results show the appropriateness of the selected design, the operability of the starter generator, and its efficiency for integration with the HP shaft.
TL;DR: In this paper, the influence of test voltage frequency on the dynamic parameters (dielectric losses and characteristics of partial discharges) of micaceous insulation of stator winding for high-voltage (HV) electric machines was studied.
Abstract: This article provides the results of studying the influence of test voltage frequency on the dynamic parameters (dielectric losses and characteristics of partial discharges) of micaceous insulation of stator winding for high-voltage (HV) electric machines The tests have been conducted using mockup samples of stator insulation with an artificial defect in the front area It has been established that the low-frequency (01 Hz) test voltage increases the dielectric loss tangent and, at the same time, reduces the peak apparent charge of external partial discharges compared to the tests at power frequencies The established ratios must be taken into account when choosing expert diagnostic evaluations during high-voltage electric-machine tests
TL;DR: In this paper, a simple means of protection of a powerful single-phase transformer with integral magnetic transformers has been suggested, which is based on the measurements of unsymmetry of the leakage magnetic fluxes of transformer windings.
Abstract: A simple means of protection of a powerful single-phase transformer with integral magnetic transformers has been suggested. The protection has a high sensitivity to the interwinding failure and is based on the measurements of unsymmetry of the leakage magnetic fluxes of transformer windings. This magnetic unsymmetry is determined by the difference of electromotive forces of windings of two magnetic transformers placed symmetrically with respect to the symmetry plane of the protected transformer. It has been suggested to produce the magnetic transformers in the form of a single-layer winding with an alternating pitch, which is wound around a textolite round or rectangular body. The length of a magnetic transformer is taken to be equal to the length of a magnetic core, which allows one to provide independence of protection sensitivity on the location of closed turns on the transformer rod. To measure the difference of the emf of magnetic transformers, the circuit of comparison with a responsive element in the form of a TT-40/0.2 or RT1-P/0.15 current relay has been used. Methods to determine a trigger threshold and sensitivity of the protection to interwinding failure as well as to ironwork failure have been suggested.