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 ...

Issues of automatic voltage regulation in local electrical networks are an important part of the overall problem of complex mechanization and automation of production processes in the mining industry. Stable voltage level is necessary for stable operation of automatic devices, more complete utilization of natural mechanical properties of electric drives, reduction/loss of electric energy in local distribution networks.