Phase-resonance Exploitation in Full-Metal 3D Periodic Structures for Single- and Multi- Wideband Applications

This paper presents a versatile full-metal 3D periodic structure based on square waveguides with non-closed resonators perforated on their walls. The complex unit-cell architecture is modelled via accurate equivalent circuits, previously characterized. The circuit model predicts the excitation of phase resonance, which will be used to optimize and design different functionalities, such as polarisation converters or absorption.

Phase-resonance Exploitation in Full-Metal 3D Periodic Structures for Single- and Multi- Wideband Applications

This paper presents a versatile full-metal 3D periodic structure based on square waveguides with non-closed resonators perforated on their walls. The complex unit-cell architecture is modelled via accurate equivalent circuits, previously characterized. The circuit model predicts the excitation of phase resonance, which will be used to optimize and design different functionalities, such as polarisation converters or absorption.

Design Optimization of Secondary Element of Single-Sided Linear Induction Motors Using a Genetic Algorithm

The article focuses on the use of genetic algorithms for the design of linear induction motors. Comparison of genetic algorithm with classical methods in the context of electrical machines designing has been carried out. The results of solving an optimization problem for two designs are presented, viz. a laboratory linear induction electric motor based on a three-phase SL-5-100 inductor and a traction single-sided linear induction electric motor of an urban transport system. The optimality criterion included maximizing the power factor and efficiency, as well as the rigidity of the mechanical characteristic while ensuring a starting traction force of at least a set value. The results of optimization of such parameters of the secondary element as the width and thickness of the conductive strip as well as the thickness of the magnetic circuit are described. The relevance of the problem of optimizing the parameters of the secondary element with unchanged parameters of the inductor is due to the fact that the same inductor can be used to build various structures, while the secondary element is created for each specific application and integrated directly into the working body of the mechanism or is a driven product. To calculate the traction and energy characteristics of linear induction electric motors, an electromagnetic model based on detailed equivalent circuits was used, taking into account longitudinal and transverse edge effects and providing a calculation time for one set of parameters of about 1 s. In accordance with this model, the electric motor is reduced to a set of three detailed equivalent circuits: a magnetic circuit, primary and secondary electrical circuits. The result of the optimization of these electric motors was an increase in the efficiency by 1.6 and 1.4 %, respectively, an increase in the power factor by 0.9 and 0.2 %, and an increase in the rigidity of traction characteristics and starting traction force.

Broadband Bi-Directional Polarization-Insensitive Metamaterial Absorber

Conventional metamaterial absorbers eliminate the transmitted electromagnetic wave by attaching the metal plate with the unidirectional absorption performance; these absorbers limit the practical applications to a large extent. In this paper, we present a broadband bi-directional metamaterial absorber by etching chip resistors on the resonators for expanding the bandwidth, and two orthogonal I-shaped structures are pasted on the both sides of the ultra-thin substrate (FR-4) instead of the metal plate for enhancing absorptance of the absorber. Simulated results show that absorptance of the designed absorber is larger than 0.9 in 1.43–2.51 GHz along the forward and backward directions under both TE and TM polarizations. Microwave experiments in the chamber are performed to verify the simulations, and the experimental results exhibit the excellent agreement with the simulations. Additionally, two I-shaped structures are orthogonally pasted on an ultrathin substrate, leading to the impedance-matching of both forward and backward directions, and the absorptance can be tailed dynamically via the middle layer of the substrate. The physics of the absorption are visualized by using a transmission line based on equivalent circuits. We claim that the designed bi-directional metamaterial absorber can be a good candidate for electromagnetic stealth and energy harvesting.

A Stator Fault Diagnosis Method Based on the Offline Motor Parameter Measurement for PMSM

The permanent magnet synchronous motor (PMSM) is used widely in electric vehicle application due to its high-power density and efficiency. Stator fault is a frequently fault in the motor as it usually works in a harsh environment. Therefore, a stator fault diagnosis method based on the offline motor parameter measurement is proposed to detect and evaluate the stator fault in this paper. Firstly, the line-to-line resistance and inductance of a healthy motor are analyzed when a DC voltage and a high-frequency voltage are excited to the motor respectively, where the DC and AC equivalent circuits at a standstill are introduced. Then, to analyze the resistance and inductance of the stator fault, an extra branch is added to the fault part to obtain the fault equivalent circuits. Accordingly, the stator fault resistance and inductance are derived, and then the resistance and inductance differences between healthy and fault motors are analyzed to provide the basis for the stator fault detection. Furthermore, the fault indicators are defined based on the resistance and inductance differences when a motor has a stator fault. Hence the stator fault severity and location can be evaluated by using these fault indicators. Finally, the experimental results from a 400 W permanent magnet synchronous motor are demonstrated to validate the proposed method.

Changes in the immitance spectra of the cement paste in the initial period of hardening

The paper analyzes changes in the impedance and admittance spectra of the cement slurry during hardening. The spectra were measured in the frequency range from 20 Hz to 2 MHz on a precision RLC meter Agilent E4890A using a homemade capacitor measuring cell. The studies in order to establish the optimal equivalent electrical circuits describing the transformation of the electrophysical properties of the cement slurry and interface phenomena in the near-electrode layer of the measuring cell from the time of hardening were carried out. The sensitivity of the parameters of equivalent circuits to different stages of cement slurry hardening has been established.

Modeling thermal processes using electrical equivalent circuits in digital twins of technical devices

One of the promising areas of digitalization of the economy today is associated with the concept of digital twins of technical systems. Digital twins based on simulation models of technical devices, which are calibrated according to the results of experimental studies on a real-time device are of great interest. Such models allow us to conduct preventive analysis of the operation consequences of these devices in various modes. Thus, a problem occurs to develop parametrically coupled models of physical processes of various natures that underlie the principles of operation of these devices. Currently, for these purposes, simulation software packages are used. MatLab Simulink software is the most popular one. However, not all such software packages provide tools to work with chain models of all physical processes that are of the user interest. Thus, the purpose of this article is to develop methods to construct digital twins of technical devices using models of arbitrary physical processes (in particular, thermal) based on electrical equivalent circuits. It unifies the task of modeling processes based on circuit theory. To develop the method to construct digital twins, the authors have applied the phenomenon of isomorphism of equations of physical processes based on the theory of circuits that is based on the theory of ordinary differential equations. The simulation has been carried out in the MatLab Simulink environment using the SimScape library for modeling physical processes. Assumptions typical for circuit theory are made during simulation. A method has been developed to construct simulation models based on the use of electrical equivalent circuits of physical processes of an arbitrary nature. In contrast to existing approaches, where the analogy method is used to simulate one of the processes of the researcher interest, it is proposed to develop a single integrated model of all physical processes underlying the operation of this class of devices. It will reduce the level of requirements for simulation systems by limiting the requested functionality of these systems to electrical circuits only. The proposed method can be used as the basis for the development of digital twins of technical devices that allow simulating their operation in arbitrary modes, considering a variety of related factors of different physical nature.