Comparison of Electromagnetic Characteristics of Single-Phase Induction Motor between Balanced and Unbalanced Operation under Different Loads

This paper varies load conditions in a single-phase induction motor and deals with consequent effects on the electromagnetic characteristics in terms of a balanced and unbalanced operation. Based on a balanced-load condition, the magnetic field, electromagnetic losses, magnetic torque are quantified by the time-stepping finite element method at six different loads. The spatial distribution of the air-gap magnetic field are investigated to characterize the existence between the load variation and unbalanced operation. The components of electromagnetic losses are analyzed in terms of main parameters degrading the operating efficiency according to the load variation. The result can show the importance of building the magnetic balance for a high performance, and the design guideline for SPIMs running at multiple operating points is discussed.

Investigation of the frequency characteristics of composite iron powders with insulating oxide coatings

This article discusses methods for studying the frequency characteristics of composite iron powders with insulating oxide coatings. The main dependences of hysteresis losses on induction for a full cycle at a frequency of magnetization reversal for various cross-sections of iron powders, sharply differing in the shape of the hysteresis curve and the values of the main magnetic characteristics, are studied, and also frequency dependences in the range of 50 Hz - 1 MHz of the figure of merit and inductance for samples based on composites are considered from powder Hoganes ASC100.29 after annealing in air, in water vapor and hydrogen at a temperature of 400 ° С for two hours. Based on the analysis of the dependencies, it can be explained by the fact that a material with a thin layer has a lower electrical resistivity, which means that the total electromagnetic losses will also be greater due to an increase in the contribution of losses to eddy currents. At the same time, the magnetic permeability at a frequency of 1 kHz differs by 30 units, and with an increase in the frequency to 1 MHz, it decreases by 10-15% for both materials. This makes it possible to use iron-based soft magnetic materials for electrical engineering.

Perfect Impedance Matching with Meta-Surfaces Made of Ultra-Thin Metal Films: A Phenomenological Approach to the Ideal THz Sensors

The terahertz (THz) frequency range is incredibly important as it covers electromagnetic emissions typical for biological and molecular processes. All molecules emit THz waves in a unique fingerprint pattern, although the intensity of such signals is usually too weak to be detected. To address the efficiency gap in existing THz devices it is extremely important to create surfaces with perfect anti-reflection properties. Although metals are absolutely reflective, here we show both theoretically and experimentally that by constructing meta-surfaces made of a superposition of ultra-thin metallic nano-films (a couple of nanometres thick) and oxide layers a unique property of perfect transmission and impedance matching may be realised. The perfect transmission rates can be as high as 100% and it may be achieved in both optical and THz regimes. The predicted effect has been observed for numerous meta-surfaces of different compositions. The effect found here is expected to impact the renewable energies sectors, optoelectronic and telecommunication industries, accelerating the arrival of the sensors for the new 6G-technology. The phenomenon is highly relevant to all scientific fields where minimising electromagnetic losses through reflection is important.