The features of changing the duration and nature of transients in electric-discharge installations (EDIs) when shunting the discharge circuit of their capacitor with an additional RL-circuit instead of by regulating the voltage feedbacks are determined. The dependences of pulsed currents and powers in the load of such installations when changing their structure are studied. Based on the mathematical simulation, the appropriate values of the time delay of connecting an additional shunt RL-circuit after the start of the capacitor discharge through the load and the energy-efficient parameters of the additional circuit are determined. The use of obtained results allows to reduce in practice the duration of the pulse currents and increase the pulse power in the load, that is, to increase the output dynamic characteristics of the EDI. In spark technology, this approach contributes to the production of electro-eroded powders with smaller sizes and

The method of multi-parameter functions is used in order to simplify the analysis of transients during the discharge of a capacitor to the electro-spark load in semiconductor electric discharge installations at changing the discharge circuit configuration for control the duration of the pulse currents in the load. On the basis of the analysis of transients in the discharge circuit of a variable structure of such installations, exact analytical expressions for calculating electrical characteristics of the circuit are obtained. It is determined the appropriate values of the connection moment and value of the additional inductance, which must be connected during the discharge of the capacitor to reduce the duration of discharge currents and stabilize the technological process in the electro-spark load. References 11, figures 8. tables 2.

The object of the research is partial discharges arising in a sample of the insulation pressboard. In most modern high-voltage direct current transmission schemes based on voltage-source converters six-pulse or twelve-pulse converters are used. The signal waveform on the direct current voltage side of a high-voltage direct current transmission is not pure direct current voltage and it has alternating current component. Since the partial discharge activity under distorted voltage is much different than that under pure direct current voltage, voltage ripples and voltage harmonics are the subject of various studies. This article examines the effect of vacuum drying the insulation pressboard on partial discharge characteristics at direct voltage ripples. The insulation pressboard was dried in a vacuum chamber with a residual pressure of 1 mm Hg. Among all the characteristics of a partial discharge, the main focus has been on the apparent charge of a partial discharge. The greater is the apparent charge value, the stronger is the destructive effect on high-voltage insulation. It was shown that drying the insulation in a vacuum chamber has the greatest effect on reducing the apparent charge of a partial discharge at direct current voltage than at alternating current voltage. After drying the insulation in a vacuum chamber, the amplitude of the partial discharge pulses was decreased by 99.3 % at direct current voltage in comparison with the moistened sample. After vacuum drying, at DC voltage, rare and very low magnitude partial discharges were recorded. The conducted research contributes to the development of methods for partial discharge detection under non-standard voltage conditions.

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Purpose. Nowadays, the upward continuous casting method is widely used copper wires and electric cables production. The electrothermal model of an induction channel furnace intended to solve the technological process modernizing issues, accounting specific production conditions, choosing the necessary electrical and energy characteristics of electrical equipment, as well as optimal operating modes. The working principle of the electrical unit of an induction furnace is similar to a single-phase power transformer operating in a short-circuited mode. Determining the parameters of this transformer is an important task requiring a specific calculation technique. Methodology. Fundamentals of electric circuit theory were applied. For further calculations, the equivalent circuit of transformer with secondary parameters transferred to the primary side was used. Results. Active resistance value of the primary winding at an operating temperature of 115 degrees Celsius is 0.005683 Ohms; inductive reactance of the primary winding is 0.008747 Ohms; active resistance of the secondary winding transferred to the primary winding at a temperature of 1080 degrees Celsius is 0.036 Ohms. Originality. The actual dimensions of the inductor for the induction channel furnace were used for the calculation. The inductor is the primary winding of the transformer, and the molten metal that fills the channel performs the role of the secondary winding. Since the secondary winding of the studied transformer, in fact, is a single short-circuited turn, then its inductance and inductive reactance can be neglected without losing accuracy. Practical value. Detailed calculation procedure for determining the single-phase furnace transformer parameters was proposed. Conclusions. This article explores the methodology for calculating the electrical parameters of the equivalent circuit of a specialized voltage transformer. These characteristics used for modeling the electrothermal processes in an induction channel furnace. Coming work for this research should focused on mathematical model enhancement and modeling of electrothermal processes in an induction channel furnace. References 12, figures 5.