Methodology of fire risk analysis in electrical installations of a production facility

This article lists the principles of fire risk assessment and management of electrical installations, provides the main terms used in this subject area, and their meanings. The article also talks about factors affecting the magnitude of fire risk (risk-forming factors). Special attention is paid to the human factor. Formulas for probabilistic assessment of fire risks of electrical installations and an algorithm for assessing the fire hazard of electrical installations, as well as a scheme of the algorithm for calculating individual fire risk are given.

Electroresistive method for monitoring the technical condition, quality, reliability and safety the supports of rolling of electrical machines

The necessity of monitoring the technical condition of the rolling supports of electric machines has been substantiated. It is proposed to use the electrical resistance of the bearing as an indicator of the technical condition the rolling support. The results of mathematical modeling of electrical resistance in the form of a function of resistance from factors of the internal environment of the bearing and modes of its assembly and operation in a rolling bearing are presented. An electroresistive method for monitoring the technical state the rolling support is proposed, which differs from the known methods by original algorithms for collecting information about the state of bearing parts, experimental studies have been carried out to confirm the efficiency of this method.

Modeling the system of a dovetailless asynchronous electric drive for conveyor mechanisms

The article considers a vector control system for asynchronous electric drive of belt conveyors, which uses an adaptive observer to control the speed of the electric drive. This allows you to increase the reliability and inter-interval maintenance of the electric drive. The requirements for the observer are determined, its mathematical description is made, and the law of adaptation is determined. In the Matlab Simulink package, a computer simulation of the proposed sensor-free control system is performed. A study of the robustness of the actuator in terms of the drift of the parameters of the motor when powered from the inverter, expressed by the integral criterion for parametric robustness. Based on the results obtained, a comparison is made and conclusions are drawn about the advantages and disadvantages of using an adaptive observer in comparison with other types of observers.

Development of a Range of Modified Multifunctional Residual Current Systems and Their Industrial Implementation

The developments of the AltSTU have been reviewed in the area of creating a new technology for preventing technogenic hazards based on the residual current devices. The residual current devices are intended for protecting people from electric shock in case of contact with conductive parts of the electric appliances and shall facilitate reduction of fire risks caused by a prolonged flow of leakage currents and fault currents resulting from them. The results of creating different modifications of protective trip circuits and their industrial use are provided.

A differential operation principle of the automatic bus transfer system pickup unit as a way of decreasing the emergency clearing time.a

A proper choice of the design and operation algorithm of emergency control devices like high-speed bus transfer (HSBT) is only possible proceeding from a study and analysis of steady-state and transient processes in emergency modes of operation (short-circuit faults, power supply disconnection, or phase open-circuit fault). The numerical experiments for studying such modes that were carried out, using the Matlab Simulink software package, on the mathematical models of an industrial power supply system involving synchronous motors connected to it made it possible to synthesize a new differential HSBT pickup unit featuring a high-speed response to emergency events. In doing so, special attention was paid to an analysis of transient operation modes with the aim of minimizing the probability of false actuations. The obtained study results have found practical application in the HSBT devices installed at the facilities of PJSC MOSENERGO. The experience gained from the operation of a new device jointly with high-speed circuit breakers produced by the Tavrida-Elektrik state-owned corporation has demonstrated essential advantages in comparison with the conventional HSBT designs.

Design of the Capacitive Dual-Mass Micromechanical Gyroscope

Development of micromechanical inertial sensors have made it possible to use them in the navigation and motion control systems. This application area imposes strict requirements on sensors. One of the ways to meet the requirements and to improve the gyroscope characteristics is to apply a dual- or multi-mass architecture of a gyroscope sensing element. This paper presents the results of dual-mass micromechanical gyroscope with a measurement range of ±450°/s design. The complex design method, including simulation at the system level, model refinement based on the results of finite element modelling, and modelling of individual electronic blocks at the circuit level, is described.

Formation of an Additional Motion Control Loop for the Nanosatellite to Adapt its Onboard Model to the Current Operating Conditions

The paper presents the formation of additional feedback in the loop of the attitude control system of a nanosatellite. Feedback is based on the assessment of the inertial characteristics of the nanosatellite. The influence of the accuracy of knowledge of the inertial characteristics of a nanosatellite on the formation of an optimal control law in the problem of reorientation was estimated. Statistical modelling has been carried out to assess the effectiveness of nanosatellite on-board sensors in the problem of identifying the inertial characteristics of a nanosatellite. Recommendations for the selection of sensor’s characteristics and time interval of data collection have been formulated.

Influence of the initial structural-phase state on inelastic and plastic strains behavior in coarse-grained samples of the Ti49.3Ni50.7 (at.%) alloy

The paper presents the experimental results of studies of the temperature dependence of inelastic and plastic strains during torsion of coarse-grained samples of the Ti49.3Ni50.7 (at.%) alloy. Investigations of the deformation behavior of the test alloy samples in the martensitic, two-phase and high-temperature states have been carried out. It is shown that the value of the summary inelastic strain reaches a maximum value of ∼ 18% under deformation of the samples in the martensitic and two-phase state, as well as in the temperature range of pre-transition phenomena.

Simulation of solar PV surface temperature with dimpled fin cooling

A significant number of cooling technologies have been developed to maintain the PV module temperature within subscribed limits. This paper represents the simulation study of active cooling forced air convection with fins attached to the back of the solar panel using CFD SimScale software. It has been first carefully validated against experimental and numerical results available in the literature. The number of fins and the shape of perforated and dimpled in each fin were varied to compare cooling performance. Three types of fins were adapted into this simulation: traditional fins, circular, and triangle perforated/dimpled fins. The effect of solar irradiation and velocity inlet was also reviewed by applying the nominal operating condition from the experimental works. Results indicated that fin channels are a very effective cooling technique, which significantly reduces the average temperature of the PV cell, especially when increasing the number of fins from 20 to 26 fins. Also, the results show that the dimpled triangle fin had the highest average temperature drop with a percentage difference of 6% compared with the solar panel cooling with traditional fins.

The strain variation during the isothermal B2→B19’ martensitic transformation in the quenched or annealed Ni51Ti49 alloy

The strain variation during the isothermal holding under constant stress was studied in the quenched or annealed Ni51Ti49 alloy samples. The isothermal strain variation was found in both samples and this strain was completely recovered on subsequent unloading and heating. This allowed to conclude that the strain variation on holding was caused by the isothermal martensitic transformation. It was found that the maximum value of isothermal strain depended on the alloy heat treatment. This value was equal to 0.5 % in annealed sample and it was equal to 6 % in quenched sample. It was assumed that the formation of the Ni4Ti3 phase during annealing led to a decrease in concentration of substitutional Ni atoms in NiTi phase that were responsible for the isothermal transformation. As a result, the less volume fraction of the martensite formed during holding that supresses the strain variation in annealed samples.