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The article presents selected aspects of the FEM-based analysis concerning resistance welding processes performed using multispot welding systems. The analysis was based on a three-spot welding machine used for the joining bars in the cruciform configuration. Both two and three-dimensional modelling was performed as the comparative analysis of two computing software packages, i.e. the commercial ANSYS Mechanical software package and the ARTAP software package, available on an open access basis. The research work involved the determination of current propagation in various welding process configurations as well as the identification of the percentage loss of welding current and power resulting from the bridging of current by neighbouring welds. The article discusses the effect of the method of the power supply and the earthing of the system of electrodes along with the welded material on the manner of current propagation. The analyses presented in the article were performed in relation to the DC power supply (inverter welding machine). Related calculations were performed using averaged (in terms of heat and resistance) material parameters.

The design considerations of AC machines with windings made of high-temperature superconductors (HTS) are presented in the following paper. The considerations were narrowed to permanent-magnet excited machines, although the results can be extrapolated to many other machine types as general guidelines. The influence of basic machine parameters and coefficients during the design of such machines are considered in order to estimate operating conditions of HTS windings. The number of poles, number of slots or slot dimensions, coil placement, and arrangement, are taken into account with the intent to fully utilize features of superconducting materials such as the capability of conducting high current density without significant losses. The attention is placed on low power machines, below 1 kW, operating at liquid nitrogen temperature (77 K). For analysis purposes, the finite element method (FEM) is used to calculate the distribution of the magnetic field and its effect on the critical current of the HTS coil. The numerical analysis is carried out in ANSYS software.

The paper presents investigation on the ideal spot weld numerical model. The weld discussed in the paper was made by the resistance spot welding of two overlapping steel sheets. The ideal weld contained three parts, i.e. two welded steel sheets and an intermediate component (connector) made of the same material. The connector was placed between the sheets, assembled mechanically and fixed. A numerical model of the ideal weld enables the elimination of all welding imperfections, including, among other things, an indent left by the electrode as well as stresses and deformations of materials present in the actual welded joint. The ideal weld was intentionally not subjected to the thermal cycle. As a result, the heat-affected zone and the molten nugget were eliminated from the model (welding area). Consequently, the entire tested (analysed) weld specimen only had the properties of the base material. The analysis presented in the paper is based on 3D FEM numerical modelling and experimental validation. The numerical model of the ideal weld (nugget surface) was investigated in relation to various shapes of the nugget (e.g. circular, square and rectangular) as well as in relation to different dimensions. The research also involved the performance of a comparative analysis including various welding conditions. The analysis was carried out to determine the highest possible value of shear force generated during a static tensile test. The results of the numerical tests were compared with the results of selected laboratory tests.

The article discusses the analysis of the propagation of current in resistance multispot welding machines and the adjustment of the cross-section of the welding machine arms aimed to compensate the asymmetry of welding current in individual welds. The analysis involved the effect of the length of multispot welding machines where the span of the arms (distance between welds) amounted up to 2 m, the arms were characterised by various cross-sections and the structural material was characterised by various resistivity (resulting from changes in temperature). The analysis was performed in relation to welding machines using a nominal welding current of 5 kA. The tests made it possible to determine the effect of changes in the value of current on the cross-section of the weld nugget.

This paper presents an experimental method for investigating the dependence of critical current on the applied magnetic-field intensity and the angular orientation in high-temperature superconductor (HTS) tapes and cables. Comparisons between critical-current measured and simulated data are presented as a function of field angular orientation. The obtained relation can be used as input data for numerical calculations or simulations for designing application devices that utilize HTS tapes and cables.

Measurement of power losses in inductive devices in highly efficient power electronic systems is crucial for choosing appropriate components. A calorimetric method for measuring power losses below 10 W is presented in the following paper to decompose the inductive devices’ power losses. A fully enclosed double-jacked calorimetric chamber is constructed to measure the temperature with digital temperature sensors TMP275, providing a resolution of 0.1 W/K. The finite element method is used with analytical calculation to estimate core and conduction losses to decompose power losses. Power losses are measured for an inductor with a 3C95 ferrite core and four types of windings, where three were made of wire with a different number of strands, whereas the fourth has been made using copper foil. All windings have similar cross-sectional areas for comparison.

Contactless energy transmission is a very convenient method of energy delivery to loads with variable location in respect of energy source. The most simple and most efficient transfer system is a transformer with an air gap. The paper is focused on analysis of properties of the transformer with relatively large air gap and the secondary winding which is a movable part. The transformer is used to deliver energy to an electronic equipment mounted on the head of drill machine. In order to increase energy efficiency and power density the capacitance compensation system for leakage inductances is applied. Since the secondary is movable, an analysis of generation of the energy resulting from spatial changes of magnetic field is carried out. The analysis presented in the paper is based on ANSYS software and is carried out mostly as harmonic one for linear models.

The main aim of this review is to present the current state of the research and applications of superconductivity and plasma technologies in the field of energy and environmental protection. An additional goal is to attract the attention of specialists, university students and readers interested in the state of energy and the natural environment and in how to protect them and ensure their sustainable development. Modern energy systems and the natural environment do not develop in a sustainable manner, thus providing future generations with access to energy that is generated from renewable sources and that does not degrade the natural environment. Most of the energy technologies used today are based on non-renewable sources. Power contained in fuel is irretrievably lost, and the quality of the energy is lowered. It is accompanied by the emissions of fossil fuel combustion products into the atmosphere, which pollutes the natural environment. Environmental problems, such as the production of gaseous and solid pollutants and their emission into the atmosphere, climate change, ozone depletion and acid rains, are discussed. For the problem of air pollution, the effects of combustion products in the form of carbon oxides, sulfur and nitrogen compounds are analyzed. The plasma and superconductivity phenomena, as well as their most important parameters, properties and classifications, are reviewed. In the case of atmospheric pressure plasma generation, basic information about technological gas composition, pressure, discharge type, electromagnetic field specification, electrode geometry, voltage supply systems, etc., are presented. For the phenomenon of superconductivity, attention is mainly paid to the interdependencies between Tc, magnetic flux density Bc and current density Jc parameters. Plasma technologies and superconductivity can offer innovative and energy-saving solutions for power engineering and environmental problems through decreasing the effects of energy production, conversion and distribution for the environment and by reductions in power losses and counteracting energy quality degradation. This paper presents an overview of the application of technologies using plasma and superconductivity phenomena in power engineering and in environmental protection processes. This review of plasma technologies, related to reductions in greenhouse gas emissions and the transformation and valorization of industrial waste for applications in energy and environmental engineering, is carried out. In particular, the most plasma-based approaches for carbon oxides, sulfur and nitrogen compounds removal are discussed. The most common plasma reactors used in fuel reforming technologies, such as dielectric barrier discharge, microwave discharge and gliding-arc discharge, are described. The advantages of solid waste treatment using plasma arc techniques are introduced. Applications of superconductors for energy generation, conversion and transmission can be divided into two main groups with respect to the conducted current (DC and AC) and into three groups with respect to the employed property (zero resistivity, ideal magnetism/flux trapping and quench transition). Among the superconductivity applications of electrical machines, devices for improving energy quality and storage and high field generation are described. An example that combines the phenomena of hot plasma and superconductivity is thermonuclear fusion. It is a hope for solving the world’s energy problems and for creating a virtually inexhaustible, sustainable and waste-free source of energy for many future generations.

The increased popularity of FDM printers expands the possibilities of manufacturing components and devices that were only possible by institutions with specialized equipment. Although not perfect in every sense, the 3D printed objects are promising supplementation for student projects that previously were only ending at the design stage. The possibility of designing and creating a functional rotating electrical machine is explored in the following paper. The material properties are derived from the measurements that allow for numerical simulations that reveal some features of such created devices.

A modern trend for industry digitalization brings new demands for the development and application of the modeling and simulation approach. It is already not enough to have only a virtual representation of the object and run it independently from the physical object. The Digital Twin (DT) aspect indicates a connection between the physical object and the corresponding virtual twin established by generating real-time data using sensors. The DT represents physical object operation throughout its life cycle, making it an essential tool for improving that object's reliability. In this paper, an application of the DT service unit for AC motor stator inter-turn short circuit fault detection is presented. According to real-time measurements, Linux Robot Operation System (ROS) simulates AC electrical machine-specific behavior in case of unbalanced stator currents and notify about possible fault appearance and propagation. Fault, such as discussed in the paper (AC machine stator inter-turn) is considered one of the most prevalent possible electrical motor failure.

International audience; The paper is based on idea realized under Erasmus+ Strategic Partnership Key Action 2 and focused on educational activities for attracting technical education to young people. The project based on exchange of good practices involves seven partners from three countries (Poland, Estonia and France). Three of them represents sector of higher education and four are schools located in the neighbour of the technical university. Unfortunately, in recent years number of candidates entering to technical universities (particularly in Europe) decreases. Partners exchange ideas how to increase number of students who starts education in technical area. Another project goal is to examine possibilities how the university can contribute in increasing quality of technical education at schools. Main project ideas and results of project activities are reported in the paper.

The main steps for designing and building BLDC motor by using 3D printing technology is described in the paper. The investigation contains an initial design of the motor, description of manufacturing process using 3D printing with polylactic acid (PLA) fiber and selected laboratory tests of fabricated prototype.

The rapid restrictions related to the COVID-19 pandemic, also known as the coronavirus pandemic, has changed the face-to-face education principles that were developed during the centuries and became the main way to transfer knowledge in higher education institutes. The distance learning is challenging for the students and makes it hard for educators to track and evaluate the student's progress. Distance learning is more challenging for the technical education, where the practical courses plays significant role in educational process. In this paper, the modifications taken place in Department of Electrical Power Engineering and Mechatronics at Tallinn University of Technology (Tallinn, Estonia) and Department of Power Electronics, Electrical Drives and Robotics at Silesian University of Technology (Gliwice, Poland) are analyzed. The experience in preparation of additional electronical materials for the students and elements of hybrid education taken in recent years was the key factor for a fast and successful transfer of technical education into distant learning.

This work describes the electromagnetic and coupled thermo-fluid dynamic analysis of an oil-natural air-natural (ONAN) distribution transformer with the main objective of studying the changes in the heat dissipation performance when the fluid employed to cool the machine is a biodegradable ester instead of mineral oil. The distribution transformer under analysis has a rated power of 315 kVA with a voltage ratio of 13.2 kV / 0.4 kV. The heat losses in the magnetic core and the windings are computed with the ANSYS Maxwell software on suitable finite element meshes. These heat losses are then transferred as volume heat source terms to appropriate finite volume meshes which are used to compute the heat conduction in the core and windings, then the heat dissipates to the oil by convection, afterwards to the walls of the oil tank and to the radiators panels and finally to the surrounding air. In the thermo-fluid dynamic model, the natural convection of the fluid flow is taken into account using a temperature-dependent density. Moreover, the heat conduction through the metal sheet of the oil tank and the radiators panels are considered. The coupled thermo-hydraulic problem is solved with Code_Satume software. The experimental data of the total power losses provided by the unit manufacturer were employed to validate the electro- magnetic model. Because the thermo-fluid dynamic numerical model is computationally expensive, only one quarter of the transformer is modelled. In addition, equivalent anisotropic thermal conductivity in the core and windings are calculated to simplify the heat conduction model in the active parts. The differences in the temperature distribution and oil flow observed between the transformer working with a standard mineral oil and a biodegradable ester are discussed. This work is carried out as part of the EU Horizon 2020 BIOTRAFO project.

International audience; The paper is focused on new educational activities focused on attracting young people for technical education. The idea is based on realization of the project under Erasmus+ Strategic Partnership (Key Action 2). The project based on exchange of good practices involves seven partners. Three of them represents sector of higher education and four are schools located in the neighbor of the technical university. Partners exchange ideas how to increase number of students who starts education in technical area, which seems a bit difficult, but engineers are very expected by the industry. The second project goal is to examine possibilities how the university can contribute in increasing quality of technical education at schools. Main project ideas and results of realized project activities are reported in the paper.

This work introduces a coupled electromagnetic, thermal and fluid flow analysis of an oil-natural air-natural distribution transformer in order to study the changes in the heat dissipation performance when a biodegradable ester is used to cool the device instead of mineral oil. The transformer has a rated power of 315 kVA and a voltage ratio of 13.2 kV / 0.4 kV . The heat losses in the magnetic core and the windings are computed with the ANSYS® Maxwell software and they are transferred as volume heat source terms to compute the heat conduction. The natural convection of the fluid flow is taken into account using a temperature-dependent density. The heat conduction through the solid walls and radiators panels are also considered. The thermo–hydraulic problem is solved with the software Code_Saturne. Data from experimental tests carried out with mineral oil are used to validate the numerical simulations. Equivalent and anisotropic thermal conductivities in the core and the windings are calculated both with a semi-analytic procedure and finite element simulations to simplify the heat conduction model in the active parts. It is found that, after reaching a steady state, the transformer cooled with the ester shows a temperature difference between specific locations at the top and the bottom higher than that cooled with mineral oil. The magnetic core and the windings also work hotter when ester is used. Finally, the analysis of the flow through the cooling ducts of the windings confirms that the oil velocity is, on average, 25% higher than the ester one.

The paper is focused on the control of resistance projection welding process applied in joining of thin-walled metal elements. The motion of electrode is generated by electric servo actuator that controls the force exerted on electrode or alternatively, just travel itself of electrode. The projection welding has been discussed for welding of 1.5 mm thick DX53 steel sheets where one sheet contains an embossed projection. Apart of electric servo actuator, another source of force has been described, i.e. pneumatic actuator (classical one), for the reason of comparison. The solution where the electric servo operates together with appropriate algorithm makes the new solution that is alternative for classical, pneumatic one. Optimized motion of electrode due to new proposed source of electrode force or/and travel, based on relevant algorithm yields improved quality of joints.

The paper is focused on numerical FEM analysis of axial flux permanent magnets (AFPM) motors dedicated for manufacturing by 3D printing. The machine has a topology of single stator - double rotor. Two types of such a machine are investigated: having two and ten permanent magnets located at each of rotor discs. The analysis is carried out as a 2D static and 3D transient. Results of analysis are magnetic flux density, induced voltage and electromagnetic torque. Comparative analysis is also presented in the paper.

The paper is focused on numerical analysis of inductive elements used for high current applications (e.g. applications with superconductors). The subject of the analysis is solenoidal coil with ferromagnetic core. The coil is analyzed in respect of geometry data having its equivalent electrical parameters (load current and inductance) fixed. Some aspects of numerical modelling based on 2D approach is discussed. Two different models are taken into consideration - axisymmetric and planar one. Nonlinear properties of magnetic core are taken into account. Results calculated for both types of models are compared and the influence of model simplification on the results is discussed. The analysis is based on commercial software ANSYS and it is carried out using scripts of ANSYS Parametric Design Language (APDL).

Assumptions related to the design of AC machines with permanent magnet excitation and armature winding made of high-temperature superconductors (HTS) and related FEM analysis are presented in the paper. The influence of machine design parameters and coefficients on the design process are being considered. The considerations are carried out in order to reduce the negative effect of magnetic field on HTS winding. The highest possible utilization of HTS wire is extremely important both from economic and engineering point of view. The considerations are limited to low power machines with fractional-slot winding up to 1 kW and cooled with liquid nitrogen (77 K). The distribution of magnetic field in slots is analyzed in details and its influence on the value of the critical current in coils calculated using FEM.

This paper presents an analytical and numerical analysis of ironless superconducting linear motor. Two types of linear motors in which excitation made by permanent magnets and windings made of HTS high-temperature superconducting tapes have been analyzed. One of the advantages of superconducting machines is the ability to reduce the size, increase power density or improve dynamic properties, but there are still many limitations that prevent the industrial application of large-scale superconductivity. One of such limitations is the influence of the external magnetic field on the level of critical currents. For this reason, the impact of the distribution of magnets in the U-channel motor on the magnetic field distribution inside the channel has been analyzed. As part of the consideration, several different configurations of magnet placement in a stator were analyzed in order to estimate the best configuration.

The article is devoted to issues related to improving energy efficiency in public buildings. The adopted research method is based on measurements of energy quality, which are the basis for the development of a plan to increase the energy efficiency of buildings. The article describes the results of measurements carried out for a selected office building, characterized by a cyclical load profile. The energy quality parameters were measured, which were referenced to the currently valid standards. As part of the study, a plan for saving and increasing the energy efficiency of the building and implementation of PV sources was proposed. Based on the results of measurements from BMS systems dozens of office buildings models for average daily electricity consumption were developed. The model was compared with the electricity production profile from the PV system to show the benefits of implementation. The article covers technical and economic aspects as the implementation of the analysis of the quality of electricity for public buildings.

Analysis of efficiency and power losses experimentally determined in two different spot resistance welding systems is presented in the paper. Efficiency of the above named systems are result of influence of such components like power converters, transformers, current leads (arms) and electrodes, which generates power losses in welding system. The goal of the investigation is the qualitative and quantitative analysis of efficiency and power losses in the main parts of selected welding machines. The analysis was carried out for two different machines, i.e. an AC welding machine (operating at grid frequency) and a DC welding machine with internal power conversion system (switching frequency 1 kHz). Systems operated using the same output current of 10 kA and were supplied by power network voltage (3×400/230 V; 50 Hz). The results are obtained by measurements of a real welding systems.

One of the most important parts of a welding system is the current loop containing the current leads and electrodes. This paper is focused on a numerical analysis of equivalent parameters (mainly inductance) and power losses of the part of a spot welding system containing current leads, electrodes and welded steel. A numerical analysis is carried out using ANSYS Mechanical APDL. The geometry and parameters of the model are based on the parameters of real welding machines manufactured by the ASPA company. The analysis described in the paper is carried out assuming DC output current with a magnitude of 10 kA. The system is made of copper elements, while the welded elements are made of two sheets of steel, each 2 mm thick. Mechanical junctions between elements, e.g. the arm and the electrode are modeled as a layer of material with higher resistivity. Comparative analysis is carried out for different geometry parameters of the model, i.e. the length of the arms, vertical distance between the arms, the width of the arms and different operational temperatures. The results of the analysis show the inductance of the current loop, current density and power loss distribution, the voltage drop along the loop and finally resistances of selected elements in the system.

International audience; In this work, we propose to study and design a coil used to magnetize, by means of a Pulsed Field Magnetization (PFM) process, an inductor of a radial flux superconducting machine with one pair of poles. Each pole contains four similar HTS bulks of 30 mm diameter arranged in a square pattern. The cryostat already exists for this application and the temperature of the HTS bulks can vary from 4.2 K to their critical temperature, in transient state. For a given primary source of energy, here a capacitor bank of 10 kJ (5 mF, 2 kV) is available, the PFM process depends strongly on the value of the coil inductance used to generate pulsed field, because it defines the waveform of the current: peak value and time constant. Thus, 3D modeling of the coil is required in order to be sure that its inductance and the magnetic field produced will provide a full magnetization of HTS bulks. From the practical point of view, we would like to achieve an average magnetization of each pole around 3 T. In this paper, numerical modeling of coils with different number of turns coupled with circuit's equations is achieved. The maximum magnetic field obtained on the HTS bulks and estimated magnetization at the top center of each HTS bulk, are presented and discussed.

The paper is focused on the analysis of transformers that are devoted for resistance spot welding DC machine. The analysis is carried out in order to get information about the influence of the design (shape of the cross-section of the magnetic core and also the way the windings are wounded) on the power properties of transformer (power loss and power density). The magnetic material taken into analysis is a ferrite one. The transformers are connected to two diode full-wave rectifier. Such connection requires special design of transformer — with two secondary windings. The transformers operate at 10 kHz of the frequency. Rating parameters are output current 10 kA, turn-to-turn ratio 50:1 and load resistance 0.8 mOhm.

In order to determine characteristics of the critical current in HTS tapes it is necessary to take into consideration different external conditions like a magnetic field and temperature. Because of a strong influence of those quantities on the critical current in the HTS tape, the influence of magnetic flux density on the critical current in the tape has been examined. In the paper, a new approach to the examination of HTS tapes is described, namely examination of the tape properties in the presence of magnetic field generated by Halbach array of permanent magnets. Such a solution is considered as application of superconducting tapes in Personal Rapid Transit systems. The influence of permanent magnets on critical current in HTS tapes is very important aspect for investigation. Dedicated test bench for characterization of HTS tapes is presented. Permanent magnets arranged in a Halbach array enable the strengthen the magnetic flux density in the vicinity of HTS tape. The distance between magnets and the tape influences on the magnitude of the magnetic flux density in the tape. The magnetic flux density generated by permanent magnets have been analyzed by FEM and measured. The critical currents at different distance between tape and magnet were measured or the Super Power® HTS tape.

This article is concerned with controlling a servomechanical force system applied in the joining of thin-walled metal elements when manufacturing e.g. car bodies. The new, i.e. servomechanical electrode force control system is both an element and a parameter of a technology used for joining metal elements by means of resistance welding. The projection welding of 1.5 mm thick DX53 sheets was used to exemplify differences between the two i.e. pneumatic (classical) and servomechanical welding machine electrode force systems. An innovative solution applied in the servomechanical force system consists in using a hybrid algorithm in order to control the force and travel of welding machine electrodes during welding. The article presents the optimisation of the new, i.e. servomechanical electrode travel system being an alternative to the classical, i.e. pneumatic electrode force control system. As a result of the undertaken optimisation it was possible to increase the repeatability of a welding process and improve the quality of joints.

The paper is devoted to numerical analysis of actuators and actuator systems with large displacement of armature. Dependence of force of armature displacement is strongly non-linear function. The system described and analysed in the paper is designed for large displacements of armature keeping force with reduced range of changes. Presented in the paper cascade system of actuators is only an example of actuator solution and it can be used in broad range of applications, including majority of applications in electrical drives. The results presented in the paper has been obtained by numerical modelling. ANSYS commercial software has been used as a tool for modelling. Classical Mechanical interfaces and APDL language allows comparative analysis of actuators. Presented results reflect static operation of actuators. It means operation at supplying by DC current and small frequency of actuator switching.

The aim of the paper is FEM analysis of single coil BLDC motor operated as drive of small piston pump. The paper contains analysis of design, distribution of magnetic field, forces and torque under static and dynamic conditions. Voltages, currents, signals waveforms are also given as the results of analysis. The cogging torque and total torque are discussed in the paper.

The estimation of the critical current (I c) and AC losses of high-temperature superconductor devices through modeling and simulation requires the knowledge of the critical current density (J c) of the superconducting material. This J c is in general not constant and depends both on the magnitude (B loc) and the direction (θ, relative to the tape) of the local magnetic flux density. In principle, J c(B loc,θ) can be obtained from the experimentally measured critical current I c(B a,θ), where B a is the magnitude of the applied magnetic field. However, for applications where the superconducting materials experience a local field that is close to the self-field of an isolated conductor, obtaining J c(B loc,θ) from I c(B a,θ) is not a trivial task. It is necessary to solve an inverse problem to correct for the contribution derived from the self–field. The methods presented in the literature comprise a series of approaches dealing with different degrees of mathematical regularization to fit the parameters of preconceived nonlinear formulas by means of brute force or optimization methods. In this contribution, we present a parameter-free method that provides excellent reproduction of experimental data and requires no human interaction or preconception of the J c dependence with respect to the magnetic field. In particular, it allows going from the experimental data to a ready-to-run J c(B loc,θ) model in a few minutes.

The structure and the results of measurements of a hybrid supplying system for the tests of an HTS tapes carrying the high amplitude AC current with DC offset is described in the paper. The system is dedicated to an examination of the second generation (2G) superconducting tapes operating under dynamic conditions (the transition between superconducting and resistive state). The tapes are bifilarly arranged and immersed in LN2. The system for the tests consists of the high current transformer (up to 500 A RMS ) and the controlled DC supply (up to 200 A). The load current in the superconducting tape is a sum of the current of the transformer (sinusoidal shape) and the DC supply (constant value). The frequency of AC component is a grid frequency (50 Hz). The structure of the system is described in the paper. Some details of the transformer geometry and parameters are presented. The results of measurements are used to estimate the power distribution in the system. Operation at different regimes (different DC to AC amplitude ratio) is analyzed. Some representative results of measurements are presented and discussed.

Artificial heart needs blood pump which satisfies not only mechanical and electrical properties, but also very important biomedical properties, particularly frictionless, with compact design and efficiency. The only one solution to meet the requirements. It is blood pump integrated with BLDC motor with rotor suspended using passive magnetic bearings. Passive magnetic bearings are solution with all required features, they are frictionless, compact and lossless. The one disadvantage is instability of passive bearing system. A new solution for stabilization of magnetic bearings is proposed in this paper. It consists in application of proper control of BLDC drive to obtain forces that together with the forces generated by permanent magnets make overall system stable. Because the only one direction (one degree of freedom) in passive bearings is unstable, it can be stabilized using magnetic forces that come from the motor. An idea of passive bearings stabilized by BLDC drive is presented in the paper. There are also selected results of FEM modelling, magnetic field and force distribution.

Coils for Transcutaneous Energy Transfer (TET) system are analyzed in the paper in respect of their equivalent parameters. Planar coils, coreless and with magnetic core are taken into account. Analysis is carried out using ANSYS software and measurements using impedance analyzer. Multiparametric analysis (where the parameters are diameters of coils, diameter of magnetic core, distance between coils and distances between coils and magnetic core) is carried out in order to obtain optimized design satisfying requirements of supply (exact values of parameters for E class inverter) and load (required output power). The analysis is carried out for system which operates at 800 kHz and delivers power of 30 W to output. The results of analysis were confirmed experimentally

In the paper topology of Transcutaneous Energy Transfer (TET) system is presented and discussed. The system is designed to supply pump of totally implantable artificial heart. The system is based on soft switched Class-E inverter connected to inductive link (transformer) and loaded by DC load through dedicated rectifier. Two battery systems are used, external battery and internal one. The first one is main source of energy, while the second one is used during disconnections at inductive link. The system delivers to load up to 50 W of power transferred through the skin at 800 kHz. Because of efficiency requirements synchronous rectifier was used inside the human body. Presented in the paper system is a modification of know in literature systems in order to obtain more reliable and more efficient system for full contactless energy transmission.

The paper is focussed on power electronics in biomedical applications. The introductory part delivers definitions of power electronics. Then there are the technical demands concerning power electronics in biomedical applications. Finally the biomedical application together with examples are discussed. Closing part of the paper embraces biomedical applications seen from the point of view of power electronics.

The aim of the paper is FEM analysis of single coil BLDC motor operated as drive of small piston pump. The paper contains analysis of design, distribution of magnetic field, forces and torque under static and dynamic conditions. Voltages, currents, signals waveforms are also given as the results of analysis. The cogging torque and total torque are discussed in the paper.

The paper describes the methodology, test rig and results of vacuum gauge tests under rotational conditions. The gauge is dedicated to measurements of vacuum in the rotor of an HTS power generator. The tests were performed using a dedicated test rig where the data of the measurements were transmitted using a Bluetooth device.

The paper is devoted to the internal backup battery for an artificial heart. The main objectives are selection of the battery type, design of the DC-DC converter and performing required tests. The numerical model of the battery is used for analysis of the system. Results of measurements will be included.

Ensuring high level of power quality (PQ) is one of most important issues in supplying in industry loads. There exist some critical types of loads that should be protected from any voltage disturbance. If any voltage disturbance (like voltage sag or dip) occurs an alternative energy source is used to ensure constant voltage amplitude across protected load. In described power conditioning system (PCS), power electronic system is connected in parallel to group of protected loads. The PCS together with protected loads have to be disconnecting from the mains in the case of voltage sag or dip occurs. Disconnection is necessary, if any voltage disturbance occurs, to prevent from delivering energy to low impedance part of power system (the mains in such case) from energy storage that is contained in the PCS (in this situation high temperature superconducting magnetic energy storage (SMES)). In described system breaking the connection between the mains and the load takes place thanks to the thyristor switch (TS). Disconnection and reconnection modes of operation of the PCS are particularly described and analysed in the paper. To obtain relatively low turn off time of thyristor switch a new method of controlling the PCS has been proposed that can assist turning off process of the TS and decreasing turn off time. The resynchronisation of the load voltage and the mains voltage of the PCS is also presented in the paper. It is used to limit the amplitude of the mains current after reconnection process. Influences of resynchronisation and reconnection processes on load voltage are also analysed. To proof correctness of designed controller the simulation and experimental results have been presented and discussed in the paper

The paper concerns the analysis of transient state (quench transition) in HTS tapes loaded with the current having DC component together with a ripple component. Two shapes of the ripple were taken into account: sinusoidal and triangular. Very often HTS tape connected to a power electronic current supply (i.e. superconducting coil for SMES) that delivers DC current with ripples and it needs to be examined under such conditions. Additionally, measurements of electrical (and thermal) parameters under such ripple excitation is useful to tape characterization in broad range of load currents. The results presented in the paper were obtained using test bench which contains programmable DC supply and National Instruments data acquisition system. Voltage drops and load currents were measured vs. time. Analysis of measured parameters as a function of the current was used to tape description with quench dynamics taken into account. Results of measurements were also used to comparison with the results of numerical modelling based on FEM. Presented provisional results show possibility to use results of measurements in transient state to prepare inverse models of superconductors and their detailed numerical modelling.

The 2D and 3D FEM (Finite Element Method) dynamical model of quench is the aim of the paper. It is based on a coupled electrical-thermal model. The small grain of non-superconducting impurity existing inside of superconducting wire initiates quench in the model. Nonlinear, temperature dependent electrical and thermal parameters are assumed. The quench propagation is modelled with the sequential coupled electric thermal analysis resulting in its 3D dynamics. The dynamics is expressed by spatial distribution of current, Joule heat and temperature. The modelling is carried out for low temperature NbTi wire and high temperature BiSCCO-2223 tape under sinusoidal current excitation and self magnetic field. Obtained computational results can be taken as a tool for optimisation for superconducting wire structure and improvement of quench protection systems in superconducting applications.

The aim of this paper is to present a thorough characterization of the toroidal HTS transformer by means of FEM analysis. The analysis was a 2D/3D harmonic electromagnetic and thermal analysis. The toroidal transformer operated in LN2 by being immersed together with the magnetic core in it, for which its power losses were acceptable. Two extreme variants of windings were analysed. The first one called parallel and the second called perpendicular. Three variants of the magnetic core were considered. In the first one the core was put outside of the windings, in the second the core was inside of the windings and in the third variant the core was outside as well as inside of the windings. The windings were made of HTS tape BiSCCO-2223/Ag while the magnetic core was made of the nanocrystalline material Finemet. The two windings, with a 1:1 turn-to-turn ratio, were uniformly distributed along the whole torus circumference. The output power, efficiency and power density are in the results of the analysis. The temperature distribution was also calculated. In summary, the performance of the transformer is better than those currently known.