This article proposes a mathematical model of an axial flux induction motor (AFIM) with one stator and one rotor. The model is based on the expression for the electromagnetic torque, which presents a function of two independent variables: the axial length of the stator core and the flux density in the air gap. This allows calculating the main dimensions of the motor with the highest possible torque density. Thus, developed model is suitable for designing the motor of specified volume with maximum torque, and solving the inverse problem of minimizing the machine volume with the specified torque. The detailed output of the model and the results of the calculations for the low-power engine powered by voltage of 7.35 V (RMS) are given. The results are validated using FEM in ANSYS software: with the outer motor diameter of 0.11 m, the flux density in it reaches 1.2 T.

The paper discusses the spectral markers of fault rotor bars in induction motor current signature analysis (MCSA). The results of the simulation of the deterioration process for a single rotor bar, as well as the results of research for various mutual bracing of two broken bars, are reported. We proposed a simple empiric technique allowing one to obtain frequencies for spectrum markers of damaged rotor bars based on simulation analysis. The set of frequencies obtained in the experimental part of the study was compared with simulation results and the results of real-life measurements. The theoretical results were verified through the experiment with the real induction motor under load. Analysis of experimental results proved that the given algorithm for spectrum analysis is suitable for early detection of fault rotor bars in induction motors.

This paper presents a methodology for creating a soft sensor for predicting the bearing wear of electrical machines. The technique is based on a combination of Park vector methods and a classifier based on an artificial neural network (ANN-classifier). Experiments are carried out in laboratory conditions on an asynchronous motor of AIR132M4 brand. For the experiment, the inner rings of the bearing are artificially degraded. The filtered and processed data obtained from the installation are passed through the ANN-classifier. A method of providing the data into the classifier is shown. The result is a convergence of 99% and an accuracy of 98% on the test data.

One-to-many wireless power transfer (WPT) is one of the leading directions in WPT systems development due to the rapid growth of consumer devices. The most challenging task is to ensure high efficiency for free-positioned receivers and provide low-cost compact WPT systems. In this paper, a transmitting metasurface-based resonator for one-to-many WPT systems is proposed and experimentally studied. The resonator design and matching method provides the self-tuning ability and allows to simplify the control and communication units of WPT systems. The resonator is composed of periodically arranged unit-cells, implemented as two crossed conductors separated by a thick substrate with a 330 pF capacitor mounted at the cross-hair of the conductors. The prototype of the proposed metasurface-based resonator is fabricated and experimentally studied for free-positioned single- and multi-receivers. The WPT efficiency to a free-positioned receiver varies from 19.7% to 84.8%. The overall efficiency for a three-receiver case reaches 83.2% which is suitable for one-to-many WPT systems.

A new generation of wireless power transfer (WPT) represents a significant advancement in the field of technology, offering a more efficient and convenient way to transmit power without the need for physical connections. The technology utilizes resonant magnetic coupling, which allows for the transfer of power over longer distances to multiple devices simultaneously. As a result, the one-to-many WPT technology should be characterized by improved safety measures and efficiency, as well as reduced electromagnetic interference. This paper develops one-to-many WPT systems based on metasurface-based resonators and demonstrates the technology to charge three smartphones simultaneously. The metasurface-based resonator is utilized as a transmitting resonator that creates a quasi-uniform magnetic field and suppresses the electric field, providing safety to the biological tissues. The performance of the metasurface-based resonator is studied numerically and experimentally. The measured DC-DC power transfer efficiency of the one-to-many WPT system based on the metasurface-based resonator is 42% for a single receiver free-positioned above the transmitter at a 5 cm separation distance. The total DC-DC power transfer efficiency of the one-to-may WPT system with three receivers varies in the range 34% -41% depending on the position of the receivers.

The paper addresses general issues related to signal analysis with Fourier transform in the context of electrotechnical tasks. A detailed description of relation among continuous Fourier transform, discrete-time Fourier transform (DTFT), and discrete Fourier transform (DFT) is provided. DFT frequency resolution increase methods are compared. Analysis algorithm of DFT results is provided. The algorithm allows increasing the accuracy of identifying harmonic composition of a signal and also revealing closely spaced harmonics that substantially differ in amplitudes.