Vol 53 Iss. 1

The asynchronous drive for mine hoisting systems has been widely used due to the simplicity of the system and low capital costs. However, its control characteristics and economic indicators are low …

The energy indicators - efficiency (η) and power factor (cos φ) - largely determine the choice of a particular variable speed drive system. The efficiency of a cascade can be determined through the power losses in the cascade ...

Dynamic parameters of electric drive operation for machines with cyclic operation mode and rectangular load pulse can be determined by known dependencies. However, there are many machines with cyclic mode of operation and triangular load pulse: swing feeders, vibrating screens, jaw crushers, etc. .....

One of the issues related to the operation of belt conveyor systems is the creation of rational electric drive systems, which would provide an optimal operating mode of the most expensive element of the conveyor system - the belt …

Voltage losses due to the gerat length of mine distribution networks prevent the normal operation of electric drives of mining machines and mechanisms. One of the effective means of compensation of voltage losses, and hence a means of ensuring normal operation of electric motors in such networks, is longitudinal capacitive compensation. Its application, however, is complicated by self-excitation of induction motors. The effect of self-excitation can be so significant that normal operation of electric motors, despite compensation of voltage losses, will be impossible ....

Analysis of materials on the failure rate shows that the cause of failure of electric motors in mining machines is mainly damage to the insulation of stator windings (80%), much less often - rotor cages (11%), even less often mechanical damage (9%). This allows us to outline the main ways to reduce the failure rate of electric motors in mining machines. Improvement of their operational reliability and an increase in service life can be achieved by: 1) improving the thermal regime of electric motors by improving their cooling; 2) increasing the heat and moisture resistance of insulation; 3) improving protection; 4) creating “constant power” drive systems ...

Manufacturers perform bench tests and performance tests of suction dredgers on water. When selecting a suction dredger for specific conditions, it is necessary to recalculate the performance characteristics from water to slurry. The insufficiently developed theory of centrifugal dredgers does not yet have strictly justified calculation formulas. Therefore, some researchers on the basis of numerous tests proposed calculation dependencies, including empirical coefficients that depend on the design and type size of the machine ...

Objectives of mine testing. In mine tests of downhole machines it is necessary to determine the design and operational characteristics of operation in given mining and geological conditions, rational mode of operation, stability of the machine, its productivity, the influence of the section network on the machine operation. To establish these characteristics it is necessary to fix instantaneous and average values of the following quantities ...

Failure of windings of electric motors of mining machines in most cases occurs due to the discrepancy between the actual thermal loads and the nameplate data of the electric motor. According to the data of the Department of Electrical Equipment of Mining Enterprises of the Leningrad Mining Institute, 80% of the failed motors of the combine “Intaugol” had damage to the windings ...

The main criterion for the productivity of the hydraulic conveying plant is its productivity of the solid phase, which, assuming that the speed of movement of water and solid particles in the pipeline is the same, can be expressed by the formula ...

If the tractive force of the engines exceeds the tractive force due to the adhesion, slippage of the wheels of the driving wheel sets will occur along with the forward motion of the locomotive. The velocity at the electric locomotive wheel rim will be the sum of the translational slip velocity. In this case, the energy consumption of the locomotive engines will increase sharply. Energy will be additionally spent on abrasion of wheel tyres and haulage rail heads ...

Mine electric locomotive haulage by contact DC electric locomotives with rheostat control has a number of significant disadvantages. The presence of a converter substation reduces the reliability of power supply of the electric locomotive haulage. Stray currents reach a significant magnitude in the DC system of rail transportation. Underground metal structures (cables, pipelines, etc.) located in the zone of stray currents are subjected to electrolytic corrosion ...

In mine signaling, interlocking, and automatic control schemes, the system of magnetic logic elements (MLE) produced by the Kalinin Electric Equipment Plant has found fairly wide application. However, the existing output devices for this system have a number of fundamental disadvantages, limiting, in some cases, the use of magnetic logic elements in mines. In this connection it is especially important to create output devices using silicon controlled rectifiers (SCR) ...

Power System Modeling. Correct and reliable construction of power supply system and distribution of electric energy, research of modes of these systems as a whole and individual elements in particular, simplification of calculations and selection of optimal parameters can be achieved by physical modeling ...

When an unloaded transformer is switched on through the capacitors of the CPC longitudinal compensation unit, undamped resonant oscillations can occur in the circuit. The frequency of these oscillations is usually 1/3 of the mains frequency (in case of subharmonic resonance) or equal to the mains frequency (in case of voltage ferroresonance). Resonant oscillations are known to be accompanied by a sharp increase in transformer magnetizing current and overvoltages both across the CPC itself and across the transformer ...

The installation of longitudinal compensation (CPC) of voltage losses in the distribution network of the mining site was first tested in production conditions at one of the sites of the Kirov mine of the Slantsy Combine in 1964. In the experimental operation of the CPC, the feasibility and efficiency of automatic voltage regulation by series capacitors in the network of the site were proved. Inclusion of the longitudinal compensation unit allows obtaining a voltage increase at the longwall face distribution point by 20-25% at motor starts and by 10-15% at nominal load ...

Estimated quarry electrical loads are mainly determined by the demand factor method Kd, i.e. the value of the estimated half-hourly load is determined by the expression …

During explosions on quarry ledges it is possible to hit elements of the quarry distribution network (CDN) with pieces of the blasted mass. This causes both direct damage, caused by damage to the elements of the CDN, and indirect damage - caused by the downtime of mining machines during the repair of damaged elements. In the periodical press there are still ongoing discussions about the distances safe for possible scattering of blast pieces. Drilling and blasting specialists have proposed several calculation formulas for determining the possible maximum flight of blasted mass pieces. But the issue of power grid equipment in the danger zone is still unclear. In practice, the question of dismantling the CDN from the danger zone is solved intuitively, depending on the experience of operating personnel ...

In order to accept adopt the most reliable variant of the quarry distribution network (CDN), it is necessary to calculate the reliability levels first of all.As the analysis of materials of emergency statistics on quarries (14 858 cases of CDN damages were considered) has shown, there is a linear dependence between damageability of separate elements of the scheme and the number of homogeneous elements. So, for example, damageability of flexible excavator cables is described by the equation ...

Currently used schemes of protection against single-phase earth faults are unreliable or relatively slow-acting devices. The fact is that the main safety criteria in the creation of such protections have usually been considered to be either random values or values insufficiently justified from the point of view of electrical safety ...

Single-phase ground faults in quarry distribution networks can occur as a result of: 1) human contact directly with live or metal structural parts suddenly energized due to insulation breakdown; 2) mechanical or any other damage to overhead or cable power lines ...

Complex mechanization and automation of production processes in underground workings is associated with the transmission of control and monitoring signals from control points to mechanisms and back. Multiplexing power networks with telemechanical signals significantly reduces the number of control cores in power or control cables or completely eliminates them, which is especially important in underground workings. One method of transmitting telemechanical signals is the multiplexing of power networks with high frequency currents. In order to determine the high-frequency parameters of networks optimal for signal transmission, it is necessary to study these networks in a wide enough frequency range ...

As it is known, the simplest and most convenient method of testing traction motors operating in open-pit mining is the method based on determining the motor heating by the RMS (effective) current. Knowledge of the effective current of electric locomotives is also necessary for a number of calculations related to the electrification of quarry railway transportation: to determine the energy losses in the electric circuit of the electric locomotive, energy losses in the contact network, etc.

The work of quarry railway transport is characterized firstly by a closed, continuously repeating cyclicity, secondly, a relatively stable number of trains engaged in the transportation of minerals and waste rock for a very long time, thirdly, a limited number of types of electric locomotives and, consequently, types of trains by weight ...

When designing a hoisting plant, the design should be based on the technological conditions (maximum productivity), labor safety and reliability of the plant, capital and operating costs ...