The low quality of voltage in the centers of supply of loads of mining sites during normal operation of the distribution network required regime measures to improve it ...
The distribution network of potash mines is characterized by a large length and energy intensity. Therefore, the voltage value in remote parts of the network often reaches unacceptable values according to GOST ...
Protection of longitudinal compensation units of CPC from overvoltages at short-circuits in the network of 6 kV can be implemented by means of thyristor arrester, included in parallel to capacitors of CPC ...
The loads of mining machine drives are characterised by significant irregularity and, as correlation analysis of the operating modes of extraction and tunnelling combines demonstrates, contain periodic components with a frequency range of 0.5–20 Hz. In extensive mine networks, cutter-loader electric motors often cannot stably sustain a load equal to their rated power. ...
In electric drive systems, capacitive 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, arises either from machine self-excitation, capacitor discharge, or a combination of both effects simultaneously. ...
Voltage losses due to the large 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 ....
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 ferroresonance of voltages). Resonant oscillations are known to be accompanied by a sharp increase in transformer magnetizing current and overvoltages both on the CPC itself and on the transformer ...
The installation of longitudinal compensation (LCC) 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 proved the feasibility and efficiency of automatic voltage regulation by series capacitors in the network of the site. Inclusion of the longitudinal compensation unit allows to get voltage increase at the longwall face distribution point by 20-25% at engine starts and by 10-15% at nominal load ...
The development of mechanization of production processes in oil shale mining inevitably leads to a corresponding increase in energy consumption of oil shale mines. In the conditions of continuous growth of energy consumption the struggle for electric energy saving and rationalization of electric power economy of mines acquires great national economic importance.
