Monitoring of lithium-ion cells using a microcontroller

Safe and efficient operation of batteries is always desired but batteries with a high energy density pose a threat to the system causing thermal breakdown, reduced performance and rapid ageing. To reduce such vulnerabilities, an optimum environment with controlled parameters is required. Four parameters have been considered for analysis, i.e. state of charge, current, voltage and temperature. The module makes a detailed analysis of the above-mentioned parameters and suggests a microcontroller-based prototype that is capable of monitoring the external factors in real time and generating relevant warnings.

Rare Crucible from Medieval Karelian Hillfort: Mineralogical Fingerprints of Functional Use

A rare crucible with an unusually large volume and a pot-shaped bottom was excavated at the Tiversk hillfort (late 13–14th century—1411 AD) in the North-Western Ladoga region (Russia). ICP-MS data showed that the crucible might be attributed to local technical ceramics. Because of its specific volume and shape, which are not typical for crucibles used in non-ferrous metallurgy in medieval Karelia, earlier it had been attributed to the technical ceramics used for the cementation of iron. The present research has revealed tin bronze metal alloy along with copper sulfide minerals recorded on the crucible walls, suggesting it might have been used in non-ferrous metal working. Thermal treatment of the crucible at temperatures above 1050 °C is evidenced by the heterogeneous composition of quartz, the thermal breakdown of biotite, recorded in the temper of the ceramic fabric, and Raman spectra characteristics of hematite.

THE INFLUENCE OF EXTRANEOUS SOURCES OF THERMAL ENERGY ON THERMAL STABILITY AND BREAKDOWN VOLTAGE OF ELECTRICAL INSULATION DURING ITS THERMAL BREAKDOWN

The article is devoted to the analysis of thermal breakdown of insulation of electrical and power equipment due to disturbance of its thermal balance. The analysis was performed within the simplest model of thermal breakdown while ignoring the temperature distribution in the insulation volume. Particular attention is paid to the influence of extraneous sources of thermal energy on the thermal stability and the breakdown voltage of the electrical insulation structure. From the heat balance equation and the condition of thermal balance disturbance between the total thermal power in the insulation and the heat transferred into the surroundings, have been found analytical expressions that take into account the influence of extraneous sources of thermal energy on the critical operating temperature and the breakdown voltage of the insulation. The influence of extraneous sources of thermal energy on the dependence of the breakdown voltage on the dielectric parameters and the cooling conditions was analyzed. It is shown that the breakdown voltage of the insulation decreases exponentially with the increase of the power of extraneous heat sources and the temperature coefficient of tgδ, as well as the deterioration of the heat transfer conditions. It is established that the critical dielectric losses in the insulation leading to the breakdown do not depend on the power of extraneous sources of thermal energy. It is proposed to increase the electrical insulation safety factor for breakdown strength relatived to its operating voltage, taking into account the extraneous sources of heat, to ensure the stability of insulation against thermal breakdown in the presence of extraneous sources of thermal energy. References 10, figures 3.

Application of a polymer nanocomposite with carbon filler to limit overvoltages in a photovoltaic element

The ability of a structure in the form of a photovoltaic element with a built-in posistor layer based on a polymer nanocomposite with carbon filler being in direct thermal contact to protect against overvoltages was studied experimentally and by simulation. It was shown that the current and voltage on the reverse-biased [Formula: see text]–[Formula: see text] junction of the photovoltaic layer are limited and decrease from the moment when the temperature of this structure reaches values close to the tripping temperature of the posistor nanocomposite to the low-conductivity state. The temperature of the photovoltaic layer has a value close to the tripping temperature of the posistor layer, which is equal to [Formula: see text]C. The possibility of realizing protection against reverse electrical overvoltages and thermal breakdown of photovoltaic systems based on photovoltaic elements with built-in layers of posistor polymer nanocomposites with carbon fillers was established.

Size and Temperature Effects on Dielectric Breakdown of PLZT Film Capacitors

The paper introduces a model of dielectric breakdown strength. The model integrated thermal breakdown and defect models, the relationship between the electric field of ferroelectric films and dimensional parameters and operating temperature (T). The thickness effect is thermal breakdown in origin, whereas the area effect is statistical in nature. This model is verified with experimental results of the lead lanthanum zirconate titanate (PLZT) films of various d (0.8 – 3 m), A (0.0020 – 25 mm2) tested under a range of T (300 – 400 K) with satisfying fitting results. Also learned is a relationship that the recoverable electric energy density is directly proportional to the square of breakdown electric field. This relationship is found viable in predicting the electric energy density in terms of variables of d, A, and T for the PLZT films.