Coupling Independent Operation in Wireless Power Transfer System without Ferrite Usage

The power transfer efficiency and output power of a wireless power transfer (WPT) system are mainly affected by magnetic coupling between the primary and secondary coils. This paper presents a constant-current series-series compensated WPT system. Based on the bifurcation criteria, kcri and Lcri, the splitting zero phase angle (ZPA) frequencies is adopted as the operating frequency. The proposed system remains fully compensated even under coupling variations, and without ferrite. The current and voltage gains at the operating frequency can be estimated through the primary current and voltage. A phase-locked loop circuit is used to track the corresponding ZPA frequency due to the coil positioning variations. Experimental results have shown that the 1-kW of output power with the satisfied efficiency of 96%.

Removal of Excess Alkali from Sodium Naphthenate Solution by Electrodialysis Using Bilayer Membranes for Subsequent Conversion to Naphthenic Acids

The processing of solutions containing sodium salts of naphthenic acids (sodium naphthenate) is in high demand due to the high value of the latter. Such solutions usually include an excessive amount of alkali and a pH of around 13. Bipolar electrodialysis can convert sodium naphthenates into naphthenic acids; however, until pH 6.5, the naphthenic acids are not released from the solution. The primary process leading to a decrease in pH is the removal of excess alkali that implies that some part of electricity is wasted. In this work, we propose a technique for the surface modification of anion-exchange membranes with sulfonated polyetheretherketone, with the formation of bilayer membranes that are resistant to poisoning by the naphthenate anions. We investigated the electrochemical properties of the obtained membranes and their efficiency in a laboratory electrodialyzer. Modified membranes have better electrical conductivity, a high current efficiency for hydroxyl ions, and a low tendency to poisoning than the commercial membrane MA-41. We propose that the primary current carrier is the hydroxyl ion in both electromembrane systems with the MA-41 and MA-41M membranes. At the same time, for the modified MA-41M membrane, the concentration of hydroxyl ions in the anion-exchanger phase is higher than in the MA-41 membrane, which leads to almost five-fold higher values of the specific permeability coefficient. The MA-41M membranes are resistant to poisoning by naphthenic acids anions during at least six cycles of processing of the sodium naphthenate solution.

Investigation of effect of electrode polarity on electrochemistry and magnetohydrodynamics using tertiary current distribution in electroslag remelting process

Transport phenomena including the electromagnetic, concentration of ions, flow, and thermal fields in the electroslag remelting (ESR) process made of slag, electrode, air, mold, and melt pool are computed considering tertiary current distribution. Nernst–Planck equations are solved in the bulk of slag, and faradaic reactions are regarded at the metal–slag interface. Aiming at exploring electrochemical effects on the behavior of the ESR process, the calculated field structures are compared with those obtained using the classical ohmic approach, namely, primary current distribution whereby variations in concentrations of ions and faradaic reactions are ignored. Also, the influence of the earth magnetic field on magnetohydrodynamics in the melt pool and slag is considered. The impact of the polarity of electrode, whether positive, also known as direct current reverse polarity (DCRP), or negative, as known as direct current straight polarity (DCSP), on the transport of oxygen to the ingot of ESR is investigated. The obtained modeling results enabled us to explain the experimental observation of higher oxygen content in DCSP than that of DCRP operated ESR process.

Surviving the Black Swan Event: How Much Reserves Should Nonprofit Organizations Hold?

Organizational survival is a primary current focus, as the unforeseen economic effects of the pandemic ravage the civil sector. Over time, however, we turn to questions of resilience: How can organizations prepare for rare, but devastating, financial shocks? Three months of funds to cover operating expenses are often described as a suitable savings target. However, organizations differ greatly in their revenue volatility, which suggests that “3 months” may severely underestimate the reserves that certain organizations should hold. We measure revenue volatility and calculate reserve fund targets for 25 nonprofit subsectors, showing sharp differences in optimal savings levels ranging up to 1 year of total expenses. We also explore organizational characteristics associated with revenue volatility. We argue for a resilience strategy that goes beyond optimizing the contents of the revenue portfolio. Funders and nonprofit practitioners should consider the broader context of financial resilience that includes correctly sized reserves as a stabilizing force.

MATHEMATICAL MODELING AND ANALYSIS OF ELECTROMAGNETIC PROCESSES IN THE THYRISTOR CURRENT REGULATOR SYSTEM - SPECIAL TRANSFORMER INSTALLATION INSTALLATION IN BCF

Peculiarities of mathematical modeling are considered and electromagnetic processes in the system “thyristor current regulator - special transformer” (TRS-ST) are analyzed. An indirect method for measuring the temperature of a die plate, which is controlled by the primary current of the CT, is proposed. A simulation model of the TRS-ST system has been created, which makes it possible to take into account the nonlinearity of the characteristics of the transformer core material and the nonlinearity of the load resistance to achieve the required accuracy of electromagnetic processes. The results of simulation confirmed the effectiveness of the developed mathematical model as the difference between the curves of transients obtained by modeling and the curves obtained during research on the experimental setup is not more than 5% and allows to further optimize multi-loop control systems with interconnected and nonlinear parameters. Bibl. 9, fig. 13.

A simplified model of a current transformer for studying relay protection operation in transient conditions

We develop a simplified model of a current transformer based on its current-voltage characteristic. This model is applicable for studying relay protection operation in transient conditions when no high accuracy or consideration of current transformer magnet core hysteresis is required. The model was developed in MATLAB Simulink using elements of the SimPowerSystems and Simscape libraries. The model uses the transformation ratio and current-voltage characteristic obtained during operational tests of a current transformer. Calculation experiments with non-linear resistance found that a currentvoltage characteristic of voltage and current values can be used to model a current transformer, rather than instantaneous values. The following conditions were simulated: for nominal currents in current transformer windings to check the transformation ratio; for opened secondary winding; with current transformer saturation by increasing secondary loading; increasing the primary current ratio and presence of aperiodic current at the start of the transition process. It was found that the developed current transformer model allows for a correct imitation of all the above conditions. To verify the model, secondary current oscillograms were obtained using real current transformers 10 kV at known primary current, which were compared with nominal oscillograms in the model. The discrepancy between the results of calculational and real experiments was no more than 10% in amplitude values, with high-quality matching obtained for current charts in the model and real current transformers. A significant advantage of the developed model is that its setting requires no information on magnet core cross-section, power line length, steel grade, and the number of current transformer winding turns.

Organization of equity accounting process technology

Introduction. The lack of a clear organization of equity accounting in enterprises with foreign investment causes problems in the formation of accounting and analytical support for management decisions not only by management but also by foreign investors, which reduces the inflow of investment into the company and the exit of investors.The purpose of the study is to clarify the content of the organization of accounting of equity in enterprises with foreign investment and study the specifics of the organization of the technology of the accounting process of equity at the stages of primary, current and final accounting.Research methods. In the process of research on the organization of the accounting process of equity were used general and special methods of cognition. General scientific methods - system approach, induction and deduction, analysis, synthesis and generalization - are used in processing information to clarify the content of the organization of accounting for equity in enterprises with foreign investment. Special methods of cognition are used to study the specifics of the organization of the technology of the accounting process of equity at the stages of primary, current and final accounting.Results of the research. According to the results of the analysis of literature sources, the content of the organization of accounting of own capital at the enterprises with foreign investments is specified.The provisions of the organization of accounting by clarifying the content of the stages of organization of accounting technology for equity in enterprises with foreign investment: primary, current and final accounting, as well as by specifying the lists of accounting information on equity (primary documents, accounting records, financial statements) , which are used in the accounting practice of enterprises with foreign investment, which necessitated the study of improving the documentation of records in accounting for equity transactions of enterprises with foreign investment.The organization of accounting of own capital at the enterprises with foreign investments on the basis of substantiation of influence of provisions of contract, constituent documents and accounting policy on the order of the organization of document circulation and formation of organizational nomenclatures of accounting is improved.The need for the formation of accounting nomenclatures for the organization of the accounting process as a whole, and the need to determine the accounting policy form of accounting and the procedure for registration of accounting information on equity in the registers of analytical and synthetic accounting.The list of provisions of the contract agreement which is defined proceeding from needs of its participants is resulted, and the aspects of legal maintenance of joint activity at drawing up of the contract agreement are defined.Perspectives. These results create prospects for the adaptation of modern enterprises with foreign investment to the needs of international capital markets, and with the help of specific organizational accounting regulations - accounting policy, which covers a set of principles, methods and procedures - the rules of equity accounting.

A STUDY ON DYNAMIC CH AMIC CHARACTERISTICS OF A NEW REMO TERISTICS OF A NEW REMOTE TRANSFORMER CURRENT CONVERTER WITHOUT COMPENSA COMPENSATING CAP TING CAPACITOR

In this research paper, analytical equations of the transient characteristics of a new remote transformer current converter without a compensating capacitor have been obtained when a stepwise, linearly increasing, sinusoidal and sinusoidal with a damped amplitude of effects was applied to their input. It has been shown that the developed current converter can be represented in the structural schemes of monitoring and control systems in the form of a series-connected real ifferentiating link without statism and inertial (aperiodic) link of the first order, and in the case of neglecting active losses in the magnetic circuit and when the converter is operating in idle mode, i.e in the form of ideal differentiating link.It has been established that the transient response of the developed current transducer has an aperiodic character when a surge primary current is fed to its input, and with a relatively very large value of the time constant of the secondary circuit compared to the time constant of the magnetic circuit, transient response approaches transient response of a real differentiating link.

RECYCLING TECHNOLOGY OF ACTIVE MATERIALS OF THE ZINC-MANGANESE CURRENT SOURCES

It is being investigated whether it is possible to develop a low-cost method for processing used Zn-MnO2 primary chemical power sour­ces, which is focused on a closed cycle of ge­nerating zinc-manganese power sources from wasted batteries. It is proposed that chemical processing reagents be replaced with less dangerous ones for the environment and people, in accordance with «green chemi» principles. The existing hydrometallurgical method of processing of primary current sources with selective extraction of the spent part of the anode mass is modified and laboratory processed. The stage of additional extraction of arsenic is entered. The proposed technological scheme avoids heavy air loads in the form of carbon dioxide emissions by eliminating the stage of burning organic matter. The use of acetic acid allows to avoid sulfuric acid discharges and to obtain high-quality for secondary production of cathode mass of new chemical current sour­ces, as well as to obtain technical zinc powder and active zinc powder using hydrometallurgical technology for anode mass production of primary batteries. Also, the presence of stages of extraction of heavy metal ions (Hg2 +, Pb2 +, Cd2 +) and Arsenic to obtain products that can be further used in other technological processes makes this technology virtually waste-free, and in the stages of recovery of acetic acid and hypochlorite – closed. Thus, the use of the proposed technological schemes allows to make such production not only a little harmful to the environment, but also for workers, as well as to simplify the requirements for technological equipment.