The article presents the principle of thermal protection of the contact overheadlineand substantiates the possibility of practical implementation of this principle for rail electric transport in the mining industry. The algorithm for the implementation of modern digital protection of the contact overhead line as one of the functions of the controller is described. A mathematical model of thermal protection is proposed, which follows from the solution of the heat balance equation. The model takes into account the coefficient of the electrical networktopology, as well as the coefficient of consumption of the current-carrying core of the cable, which determines the reduction in the conducting section from contact erosion and the growth of oxide films. Corrections for air flows are introduced when receiving data from an external anemometer, via telemechanics protocol. The mathematical model was tested by writing a real thermal protection program in the C programming language for the bay controller, based on the circuitry of which is the STM32F407IGT6 microcontroller for the microcontroller unit. Verification tests were carried out on a serial bay controller in 2020. The graphs for comparing the calculated and actual values of temperatures, with different flow rates of the current-carrying conductor of the DC cable, are given. To obtain data, telemechanics protocols IEC 60870-104 and Modbus TCP, PLC Segnetics SMH4 were used.
In last 20 years segment of electric drives with permanent magnet synchronous motors has increased. This type of motors has better technical characteristics compared to induction motors, but has problems in actual implementation, one of which is the requirement of rotor position data. It is possible to implement with use of sensors or without them by means of motor state observer. The paper describes problems of sensorless vector control system for permanent magnet synchronous motors. The vector control system with state observer for permanent magnet synchronous motors is described. Synthesis of sliding mode observer for rotor speed and position is presented. The algorithm is implemented by development of model in Matlab Simulink environment with support by Texas Instruments processors support blocks. Experimental comparison of results of rotor angle state calculation and the data obtained by rotor position sensors was conducted. Research objective is a development of control algorithm, which has required precision for calculation of rotor start angle, high range of speed regulation and resistance to drift of motor parameters.
The most common device for protection against overvoltages is a valve-type arrester. Due to obsolescence it is proposed to replace valve-type arresters with nonlinear overvoltage limiters or multi-chamber arresters. Modern recommendations for the selection of means for protection against overvoltage take into account not all factors when placing protection devices. For example, when replacing valve arrester with non-linear overvoltage arresters (arrester), accidents often occur. Often, due to the replacement of protective devices, there are violations of the operating conditions of new devices, since in the design of the arresters, they are placed in place of the vale-type arresters. Nonlinear surge arresters have a number of reliability problems, for example, due to frequent single-phase ground faults, thermal instability problems occur. Therefore, as an alternative to arresters in urban distribution networks, it is proposed to use multi-chamber arresters – devices that are a series of discharge chambers in silicone rubber. The purpose of this work is to calculate the electric field strength and conductivity at the exit from the discharge chamber of the multichambe arrestor, study the effect of multichamber dischargers on distribution networks, build up the dependence on the voltage and conductivity of the plasma exhaust gases, depending on the distance to the multichambe arrester.