Based on the results of conducting comprehensive studies of power consumption of the open-pit mine of the mining and metallurgical plant in high altitude conditions, the issues are considered related to ensuring safe operation of electric motors supplying excavators. Experimental studies were carried out in a 6 kV electric network, from which the excavators and drilling rigs are powered. The design schemes of sections of the electric network are given, the characteristic of the main equipment is provided.
One of the problems in the operation of the excavators in high altitude quarries is a decrease in their productivity due to the need in periodical repair of the insulation of synchronous motor drive of the converter unit.
The influence of switching overvoltages on the synchronous motors insulation integrity of the excavator is established.
The scheme of a protective device is presented, which allows protecting the isolation of the excavator engine from atmospheric and internal switching overvoltages.
The principle of synthesis of the surge suppressor is to determine the maximum amplitude of free component of the switching voltage and the corresponding frequency with the subsequent installation of the quenching spark gap and the shunt capacitance, calculated according to a certain amplitude and frequency. Therefore, the main measure providing protection of the insulation of the drive motor should be the suppression of overvoltage, which has a fundamental frequency of 8–8.2 kHz.
The network transient in the open-pit electric circuit — a synchronous motor is investigated, and the parameters of the shunt capacitor are determined. It was found that the selected capacitor is capable of long-term operation in an electrical installation at a frequency of 50 Hz. In order to reduce the effect of additional capacitance on the frequency, it is necessary to install capacitors together with the arresters in a 6 kV input cell.