High-voltage line-start permanent magnet synchronous motors (HVLSPMSMs) are prone to inter-turn short-circuit faults, which not only result in a significant increase in current but also exacerbate motor vibration. To accurately identify the frequency-domain fault characteristics of the motor under inter-turn short-circuit conditions, an improved wavelet packet energy gain ratio analysis method is proposed. Firstly, a two-dimensional transient finite element simulation model is established, and the validity of the model is verified through experimental data. On this basis, the inter-turn short-circuit fault state of the motor is further analyzed, and the corresponding fault signals are extracted. Secondly, the improved wavelet packet transform (IWPT) is applied to analyze the fault current and vibration signals. By combining the energy gain ratio, fast Fourier transform (FFT) is conducted on the sensitive wavelet packet coefficient nodes to extract the fault characteristics of the current and vibration signals by comparing the frequencies before and after the fault occurrence. Finally, a comparison with traditional wavelet packet analysis demonstrates the reliability and accuracy of the proposed method.

This study addresses the issues of high energy consumption and low efficiency in conventional electric heating snow-melting systems for railway turnouts. A novel system is proposed that integrates electromagnetic induction heating with traditional electric heating to optimise energy transfer pathways and enhance energy utilisation efficiency. The system enables dynamic adjustment of heating power, thereby supporting adaptive operation under varying environmental conditions. Through theoretical analysis, temperature field simulations, and experimental validation, the energy regulation mechanism and performance characteristics are examined. Results show that, under full snow-cover conditions, the proposed induction heating system reduces snow-melting time by 76.9% compared with traditional electric heating, while achieving a 29% efficiency gain under snow-free conditions. Steady-state temperature rise tests demonstrate close agreement between simulations and measurements: directional heat transfer efficiency improves significantly, with the average rail temperature decreasing by 8.5% and the air temperature in the working area increasing by 15%. Additionally, the system increases the ice- and snow-melting rates by 0.4 and 0.8 times, respectively, while reducing energy consumption by 30–40%. An optimised composite thermal structure further enhances heat utilisation. This study provides both theoretical and practical insights for advancing turnout snow-melting technology and its engineering applications.

This paper analyzes the transient thermal field in a system of two parallel con-ductors. The skin and proximity effects are taken into account. An analytical method based on Green’s function is developed to determine the field distributions. The Green's function was determined analytically, and due to the complex forms of the expressions describing the current densities, the integrals resulting from the Green's identity were calculated nu-merically. In addition, important parameters determining the dynamics of the conductors, were also calculated: heating curves and thermal time constants. The influence of selected material parameters on the corresponding thermal field distributions is examined. The cal-culation results are positively verified using the finite element method.

The no-load magnetic field of a hydro-generator significantly impacts the quality of its no-load voltage waveform and the grid power quality and power system stability. As a vital element for ensuring the safe and steady operation of hydro-generators, the damping winding structure directly affects the state of the no-load magnetic field. Particularly, horizontal hydro-generators, such as tubular turbine units, feature confined and irregular internal spaces that lead to more intricate and intense distributions of the magnetic field. Therefore, to improve the quality of no-load voltage waveforms, grid power quality, and overall power system stability, it is essential to examine how variations in damping winding structure types affect the no-load magnetic field in these generators. This paper considers a specific 34-MW large tubular turbine generator as an example. A 2D transient electromagnetic field model was developed to investigate the effects of four damping winding structures—fully damped, semi-damped, isolated damping bar, and solid-steel pole—on the mag-nitude and distribution of the no-load magnetic field, the quality of the no-load volt-age waveforms, and the eddy-current losses within the damping system. The research directly supports the design and manufacturing processes of tubular hydro-genera-tors and ensures the safety and stability of generator and power system operations.

Linear circuits with constant parameters are typically analysed based on their frequency characteristics, assuming the invariance of harmonic signals as they pass through the system. However, in linear periodically time-varying circuits, this invariance does not hold. The output signal in such circuits is a periodic signal composed of harmonic compo-nents at various frequencies determined by both the input signal and the periodic variation of the circuit parameters. This results in a frequency spectrum that includes harmonics be-yond the frequency of the input signal, influenced by the interaction between the input and the parameter variations. This paper investigates the behaviour of parametric devices by examining specific frequency ratios between the input signal and the variation in circuit parameters. The results are demonstrated using a parametric amplifier model and a long transmission line, analysed in the frequency domain.

To solve the problem of excessive torque pulsation in surface-inset permanent magnet synchronous motors, a non-uniform three-segment surface-inset Halbach permanent magnet synchronous motor structure based on an eccentric magnetic pole is proposed. Firstly, the electromagnetic performance of the motor structure is analysed using the finite element method to establish the motor simulation model. Secondly, Pearson correlation analysis was used to stratify the initially motor structural parameters into strong and weak layers. Optimization is carried out using an improved multi-objective particle swarm optimization algorithm, Taguchi's method and parameter scanning method, respectively. Finally, simulation experiments were carried out using the finite element method and com-pared with the electromagnetic performance of the motor before optimization. The results show that the optimized proposed structure has suppressed the torque pulsations, significantly reduced the cogging torque, improved the air gap density sinusoidality and sup-pressed the harmonic amplitude, effectively improving the electromagnetic performance of the motor.

Renewable energy sources have rapidly developed over the past few years. The stochastic nature of the generated energy in photovoltaic systems (PV) and wind power plants is causing more interest in energy storage systems (ESS). In commercial installations, deterministic methods are used to control the power of the storage, which is not efficient. Developing algorithms that optimize economic and technical aspects is necessary. Methods based on computational intelligence (CI) can be a solution. The paper presents a novel CI algorithm for optimizing power flow in microgrids using the particle swarm optimization method. The economic and technical efficiency of control is achieved by combining multi-ple criteria in the objective function. The solution is universal, scalable, and can be applied to any industrial or residential microgrid. The method uses short-term forecasts of local generation and load and specifications of ESS, ensuring that technological constraints are maintained. Analyses were conducted for a whole year for a real industrial microgrid. The paper presents the selected results of the study. The efficiency of the proposed algorithm is compared with the results obtained by a deterministic algorithm aimed at maximizing au-toconsumption. Using the PSO algorithm resulted in an economic effect of €6 635 with 461 full discharge cycles, compared to €2 287 and 110 cycles for the deterministic approach, meaning an increase of more than 2.5 times. However, such storage operation requires more intensive work, affecting its lifetime. Further research can develop objective functions that, without compromising economic effects, support microgrid operation: improving power quality, minimizing voltage fluctuations.

In this paper, the torque generation mechanism of the reverse salient permanent magnet synchronous machine (RSPMSM) is investigated. The magnetic equivalent circuit (MEC) and the equivalent reluctance of different magnetic circuits are used to determine the air-gap magnetic density without slotting. By incorporating the influence of the slotted Carter factor, a model for the air-gap magnetic density at no-load is deduced and compared to finite element analysis results. The strong agreement observed between the analytical method and finite element analysis validates the precision of the proposed methodology. Moreover, the Maxwell stress method is employed to analyze and demonstrate the genera-tion mechanism of electromagnetic torque. The contributions of the fundamental wave and each order harmonic to the torque components and their proportions are determined. This analysis provides valuable insights into the generation process of torque in the machine. Additional prototype experiments were conducted to verify the validity of the theoretical analysis and finite element simulations. The experimental results further confirm the accu-racy and validity of the proposed methodologies.

RF energy harvesters require a precise design and verification. Power conversion efficiency (PCE) is affected by a number of factors. Among others, there are: design of emitting and transmitting circuits, transmission conditions, frequency, bandwidth and dis-tance between antennas. All of those factors contribute to the final effectiveness of RF en-ergy harvesting (RFEH) circuits. This is why it is important to standardize conditions of simulating and measuring the circuits performance. Only then it will be possible to compare usefulness of different designs. This article discusses such conditions and proposes some standardizations.

The hybrid excitation starter generator (HESG) of range-extended electric vehi-cles is at risk of permanent magnet (PM) demagnetization under overload conditions. Therefore, this paper analyzes the operating process of PMs and the impact of armature reaction fields on PM operating points and demagnetization under various operating condi-tions. The variation patterns of average flux density operating points and minimum flux density values in the HESG under different load conditions are derived. The demagnetiza-tion points of each PM and their contributing factors are determined. Furthermore, the pa-rameters of the magnetic isolation air gap between the PMs are optimized while considering leakage flux and demagnetization at the ends of the PMs. The simulation analysis and pro-totype test results show that a reasonable design and optimization of the ends of PMs can effectively enhance the demagnetization resistance of PMs and improve the output perfor-mance of HESG.