Vol 70 Iss. 1

The main directions for the development of the national economy of the USSR in 1976–1980, approved by the 25th Congress of the CPSU, provide for a broad scope of work to improve efficiency and quality. …

The development of the excavator drive based on the thyristor converter–motor (TC–M) system was carried out jointly by researchers from VNIIElektromash and the Leningrad Mining Institute named after Plekhanov. The design and manufacture of the power section of the thyristor converters were undertaken by the Tallinn Electrotechnical Plant named after Kalinin. The reconstruction of the EKG-4.6 excavator, involving the replacement of the generator–motor system with the thyristor converter–motor system, was performed by the Apatit Combine. ...

The formation of accelerations and dynamic torques in electric drives with subordinate control means that elastic deformations in the transmission elements begin to have a significant effect on the law of motion of the output (actuating) shaft. Therefore, special attention is paid to an in-depth study of the dynamics of electromechanical systems incorporating elastic couplings. The dynamics of such electric drives are investigated using logarithmic frequency characteristics, based on which the feedback (FB) coefficients and transfer functions of corrective elements are determined to optimize transient processes.. ...

Operational experience with drilling rigs of the SBSh and BASh types shows that during operation, vibrations arise in the drill string, which are transmitted to the rig platform. These vibrations limit the allowable level of technological parameters and ultimately reduce the rig's productivity. The vibration level can be reduced by adjusting technological parameters, as well as by improving the design of the rig's rotary-feed mechanism. Vibrations of the rig's center of mass are caused by the disturbance introduced into this system by the drill string. ...

Thyristor DC regulators, or, as they are called, DC pulse converters, in control systems containing electrical machines, prove to be more convenient than adjustable thyristor rectifiers in a number of cases. The use of controlled rectifiers is often complicated by distortion of the supply voltage waveform. ...

There is no consensus on the optimal dynamic parameters of electric motors used to drive coal and roadheading combines. It is known that the operating mode graphs of these machines are characterized by extreme non-uniformity and obey only probabilistic laws. ...

The loads of mining machine drives are characterized by considerable non-uniformity and, as correlation analysis of the operating modes of mining and tunnelling combines shows, contain periodic components with a frequency range of 0.5–20 Hz. In long mine networks, cutting-loading electric motors often cannot stably carry a load equal to their rated power. ...

In electric drive systems, capacitor braking of squirrel-cage induction motors is employed either autonomously or in combination with other operating modes. The braking torque on the motor shaft, depending on the circuit configuration and initial conditions, results either from machine self-excitation, capacitor discharge, or a combination of both effects.

Vector control of AC machines differs from conventional frequency drive control systems in that the mutual position of generalised electromagnetic quantity vectors is taken into account when generating control signals (the voltage vector). The rationale for such a consideration becomes apparent upon analysing the expressions for electromagnetic torque. ...

When employing thyristor frequency converters (TFCs) in block control systems of AC variable frequency drives, the converter is controlled by a two-phase AC signal modulated in magnitude, frequency, and phase. …

Based on the principle of output voltage formation, direct frequency converters are divided into two main types: thyristor-based direct frequency converters with natural commutation (DFC-NC) and thyristor-based direct frequency converters with forced commutation (DFC-FC). In DFC-NC, the output frequency is formed through natural commutation within a half-cycle of the output voltage. ...

For the analysis of the spectral composition of the output voltage in the previously proposed thyristor-based direct frequency converter with forced commutation (DFC-FC), we shall employ the following expression…

The application of variable frequency drives in medium-power hoisting installations enables significant improvement in reliability indicators and enhancement of the system's dynamic characteristics. …

The increase in labor productivity in mines and the improvement of miners' working conditions have led to the widespread introduction of mining complexes with coal-cutting machines. To ensure high operational efficiency under various conditions, coal-cutting machines must include regulation of both feed and cutting speeds. ...

The control of electromagnetic transients in variable frequency drives based on synchronous machines can be achieved by applying vector control principles. The fundamental concept of vector control involves transitioning from natural electromagnetic stator variables - components of the generalized stator current and voltage vectors in stationary stator coordinates - to new variables representing components of these same vectors in rotating coordinate systems. ...

Main ventilation fan installations at mining enterprises represent the most energy-intensive consumers. Significant energy losses and low efficiency of ventilation systems are attributed to substantial deviations between actual ventilation regimes and design parameters. This occurs because main ventilation fans are selected for the entire service life of the enterprise based on the ultimate maximum design values of gas emission, explosive quantity, production volume, workforce numbers, etc. Consequently, the determination of fan operating modes for mine ventilation networks often proves insufficiently precise. ...

In certain cases involving the mechanization of maintenance and auxiliary operations related to ball mills, direct frequency converters with a limited output frequency range are employed. These operate in short-term duty modes that do not require optimal converter output voltage waveform or high precision in maintaining thyristor firing angles. On the other hand, such devices typically must meet enhanced requirements regarding noise immunity and reliability, as they are installed in industrial premises with high levels of electromagnetic interference. ...

The slow-turning device for a ball mill drum, implemented via a thyristor-based direct frequency converter-synchronous motor (DFC-SM) system with a simplified noise-resistant pulse distribution system, accomplishes sequential energization of the mill motor's stator windings from a DC voltage source in a specific sequence. ...

Nuclear engineering provides particularly suitable conditions for implementing measurement systems capable of continuous monitoring of average fluid density without disrupting flow patterns. Depending on pipeline parameters and fluid type, such measurements can be based either on scattering phenomena or on absorption of ionising radiation. ...