Soft switching systems in three-phase voltage source inverters usually require the use of additional elements, such as transistors, capacitors and inductors. Contrary to the existing solutions, in the proposed soft switching system, the danger of an abrupt discharge of the capacitors through the conductive transistor does not occur. Moreover, there is no risk of interruption of the inductor current, which usually causes damage to the transistors. In the paper principles of the system operation are described in detail and rules of component selection are presented. Laboratory tests were performed for different operating conditions. The test results have confirmed the operation correctness of the three-phase voltage source inverter with the proposed soft switching system.

This paper presents the method of rotor magnetic pulling tensioning force calculation, caused by the static radial rotor eccentricity. The method is applied to calculate the total force acting on the rotor of high-speed permanent magnet (PM) synchronous machine (PMSM). The calculations are based on 2D simulation of magnetic field distribution in the active part of the machine, taking into account the saturation of the magnetic circuit and the spatial harmonics of the air gap magnetic flux in the no-load mode and in the rated mode.

In the paper, the authors present the results of a numerical study of a magnetorheological (MR) damper prototype operating in the so-called squeeze mode. The analyzed prototype allows achieving a symmetrical response in both directions of piston motion. The authors show the results of magnetostatic analyses of the electro-magnetic circuit of the device and lumped parameter model using calculations of the control circuit and the damping force output.

There are many existing models for the interaction of a pantograph–catenary system. The authors propose a specific model, which is amended by taking into account the dynamic part of the motion equation. This model was compared to another attempt and conclusions were drawn. A numerical study was performed using the Matlab Simulink Environment.

The subject of the study is to analyze the effectiveness of early detection of damage to the stator winding with two parallel branches in the cage induction motor, by evaluating changes in the waveforms of branch currents in steady state operation. Harmonic components of the Fourier spectrum of circulating current, defined as the difference between the transient values of currents in the branches of the winding, were adopted as the indicators of branch current change evaluation. For a given low-power motor, several cases of a section short- circuiting in one of the winding branches were examined, for both symmetric and asymmetric air gap and for resistive symmetry and asymmetry of the rotor cage. The studies show a greater influence of damages on the changes in the amplitudes of selected harmonics of the circulating current, in comparison to changes of the stator phase current corresponding harmonics.

The paper presents the methodology of determining the distribution of flux density in the magnetic circuit of a 3-phase axial flux machine with permanent magnets located on the rotor. It allowed to create an analytical dependences of the inductances and flux linkages. Particular attention was paid to such processing of mathematical model equations, so as to create a possibility to determine the machine properties in steady state on the basis of equations, without even having to use quantitative solutions. The theory of linear differential equations used here, with periodically variable coefficients, allowed to determine the Fourier spectra with respect to winding currents and electromagnetic torque in steady state operation.

Electrical discharge machining is a process of machining a work-piece to a desired shape by using the eroding effect of electric spark discharges. A gap width controller is one of the key components of each electrical discharge machine. It is gap width controllers that mainly determine the machining speed and accuracy. This article describes a gap width controller based on fuzzy logic. The control algorithm operates according to the number of short circuits, open circuits and normal pulses that occur within a control period. A specially developed PC application allows for accessing and modifying electrical discharge machining parameters.

The paper presents the combined control of a six-phase squirrel-cage induction motor with the application of Sliding-Mode Control and Direct Field-Oriented Control (SMC-DFOC). The mathematical model of the six-phase squirrel-cage induction motor has been presented. The design procedure of the control structure of SMC-DFOC has been described. Simulation studies on the considered control system have been carried out and the results of the simulation studies have been presented and discussed.

The article presents the global distribution of energy losses in a DC electric traction in specific cases and the impact of changing parameters on the efficiency of electricity transmission on the railway.

This article presents the implementation of the low-frequency measuring method of current and voltage RMS values as well as active and reactive power of a two-terminal network, which is supplied by a sinusoidal voltage of 50 Hz. The implementation was made on a typical compact PLC-FX3G Mitsubishi Electric controller. This controller has a relatively low computing power, and when control tasks and measurements are performed simultaneously, the measurement method must be simple in order to match the limited computing power of the controller. This article describes how to implement the low-frequency measuring method onto the controller. It also presents the laboratory set for testing the controller and application. The paper also presents the results of measurements and calculations, in particular the impact of measurement time delays on errors of the RMS voltage and current values as well as active and reactive power values.

This paper presents the results of an analysis of signals recorded in different inter-turn short- circuit states in the stator windings of a squirrel-cage motor operating under a constant load. The analysis was carried out in a time-frequency domain using a simple orthonormal wavelet base that can be used in a real system without the need to acquire specialist software. The choice of analytical was associated with the existence of a periodic energy flow between adjacent frequency bands, thus making it difficult to diagnose the Fourier analysis. The aim of the study was to gather data necessary for the development of a real-time diagnostic system. Magnetic axial flux, the zero voltage signal, the short- circuit current, vibration acceleration, sound pressure, electromechanical torque, currents and phase voltages were tested as diagnostic criteria. The paper presents the main results of the analyses of magnetic axial flux signal and conclusions.

The paper presents a special algorithm and software for the analysis of coupled electromagnetic-thermal phenomena in a squirrel cage induction motor. In the proposed model the nonlinearity of the magnetic circuit, the movement of the rotor, the skewed slots and the influence of temperature on electrical and thermal properties of the materials have been taken into account. In order to verify the developed algorithm and software, the startup process of the motor has been examined, among others. The results of computations have been compared to the measurements.

The article is about a range of issues concerning the possible use of track circuits, consisting of rail lines and impedance bonds for continuously monitoring traffic parameters of a rail vehicle moving within a separated track section. The solution to this problem may be useful in many applications and various types of rail traffic control systems that use track circuits as a source of information about the track block occupancy. One possible application may be in automatic railway crossing signalling systems (ARCS) for approach sections. In that application, the carried out measurement of the position and speed of a rail vehicle allows to determine a pre-warning time for the railway crossing.

The paper presents the wind energy conversion system with a direct driven Permanent Magnet Synchronous Generator (PMSG). The system consists of a wind turbine with a PMSG, the Machine Side Converter (MSC) and the Grid Side Converter (GSC). In order to control the MSC, the Direct Torque Control with Space Vector Modulation (DTC-SVM) has been applied. To achieve the maximum power from the wind turbine, the Maximum Power Point Tracking algorithm has been used. In order to control the GSC, the Direct Power Control with Space Vector Modulation (DPC-SVM) has been used. In order to obtain high power quality, the LCL grid filter has been used in the GSC. The performed simulation studies confirmed the high effectiveness of the Direct Torque and Direct Power control method.

In this paper, an application of the PKmin program for functional decomposition of multi- input multi-output combinational circuits is presented. The main focus is on balanced multi- level decomposition of logic circuits into minimal number of blocks, such as LUTs in FPGAs. Reduction of the input redundancy is available. Decomposition schemes include parallel, joint/ disjoint serial and a mixed one. The decomposition with PKmin can be automated by means of a heuristic algorithm or can be supervised by the designer. A distinctive feature of PKmin is the visualization of the design steps and the final layout of blocks and their interconnections. PKmin is compared in an example with the program DEMAIN.

The results of developing a method of distribution of the downlink frequency and time resources under the LTE technology were presented. The proposed method is aimed to ensure the quality of service of wireless for users by allocating the required user station capacity in the downlink. A comparative analysis of the proposed method was conducted with known solutions of the distribution of time- frequency resources of the LTE technology in terms of the overall performance of the downlink, the degree of balancing capacity, as well as the confidence level of allocating the required capacity to user stations.

The goal of this paper is to verify the usefulness of the expert system as a tool supporting the Failure Mode and Effect Analysis (FMEA). For the purpose of this study, a computer program acting as an expert system for FMEA has been implemented. The knowledge base of the expert system contains the medium voltage current transformer data. The Expert system structure, principle of operation and the data acquisition process were discussed. An expert system has been tested during the FMEA analysis of the medium voltage current transformer.

The Internet of Things (IoT) is an emergent technology that offers great opportunities to enhance economic indices and productivity of enterprises, to improve the quality of consumers’ lives, and to enable more efficient use of resources. In this paper, the authors propose an approach to Microcloud-based IoT infrastructure management to provide the desired quality of IT services with rational use of IT resources. Efficiency of IoT infrastructure management can be estimated by the quality of services and the management costs. The task of operational service quality management is to maintain a given level of service quality with the use of minimum IT resources in IoT environment. The proposed approach allows the efficient use of resources for IT services’ provision in IoT ecosystem through the implementation of service level coordination, resource planning and service level management processes in an integrated IT infrastructure management system.