Calculation of Load Diagrams and Static Characteristics of Multimotor Electric Drive Systems using the Methods of Equivalent Forces and Reduced Moments

This paper presents the calculations and construction of load diagrams and the static characteristics of individual mechanisms of a mining roadheader, which form a multimotor electric drive system, using the methods of equivalent forces and reduced moments. The productivity of the mine and the roadheader are calculated. The operating forces of idle and on-load mechanisms are calculated, and operation time intervals and a complete working cycle are determined. The load diagrams of mechanisms are constructed and their kinematic diagrams are designed. Based on the calculations performed, asynchronous motors with a short-circuit rotor, which have the closest power values and are suitable in terms of voltage and mode of operation, were selected from the catalogue. The gear reduction ratio is calculated, static resistance moments, and operation speeds to the motor shaft are specified. The static characteristics of the most powerful electric motor of a mining roadheader – or cutter – are formulated. The high accuracy of the calculations was confirmed by computer simulation, which showed minimum errors.

Computer modeling; Electric motor; Equivalent force; Load diagram; Mine; Power calculation; Reduced moment; Roadheader; Static characteristics

        Diamond production consists of three main stages: mining, processing and manufacturing of jewelry, and retail. Rough diamond mining is geographically concentrated in South Africa, Russia, Australia, and Canada. Alrosa is developing Russian diamond reserves; it produced 36.7 million carats in 2018. Alrosa's experience in mining rough diamonds may be of interest to other companies (Chanturia et al., 2015). The company’s largest deposits are Mir, Yubileinaya, Udachnaya, and Internationalnaya. They are located in Western Yakutia, where the mining of diamond-bearing rocks is now being actively developed (Chaadaev et al., 2015; Sutresman et al., 2017).

        A literature review showed that the main direction of current developments in the complex  mechanization  of  tunneling  and  mining  operations  in  the  diamond-mining industry is the introduction of combined methods for carrying out work (Sutresman et al., 2017; Hrinov and Khorolskyi, 2018; Cehlar et al., 2019). This determines the relevance and practical significance of the presented research. Its novelty consists in an integrated approach to the application of new methods of calculation and selection of both the mining roadheader itself and its individual mechanisms, since at present, most Alrosa underground mines use the drilling-and-blasting method, which becomes insecure with the deepening of mining operations and the release of gases and oil.

        The level of mechanization of tunneling and mining operations in the global diamond-mining industry in 2018 reached 80%. In some Canadian mines (for example, Ekati and Diavik), it exceeded 90%. At the same time, in Russia use of the roadheader method does not exceed 50%. Light and medium roadheaders are mainly used. Heavy mining roadheaders account for only about 20% (Odnokopylov et al., 2019).

        Voest-Alpine Bergtechnik GesmbH (an Austrian manufacturer of mining equipment) produces medium and heavy mining combines of the AM series, which are self-propelled, tracked machines with a boom-type cutter and loading device in the form of paired pallet handles on the inclined rotary table with an independent drive (GES.M.B.H, 2009). The stage of development of pit reserves through an auxiliary ventilation shaft, the size of which does not allow for the transport of the well-proven mining roadheader AM-105 to a working face, started at the Internationalnaya underground mine in Western Yakutia. Prior to this, the AM-105 roadheader was used to extract minerals at the 8-11 horizons of the mine and, having worked out 32 thousand m³/h, depleted its resource. In general, the mining equipment of SANDVIK, which includes Voest-Alpine Bergtechnik GesmbH, has proven itself well not only in the Russian North, but also at the Letlhakane, Jwaneng (Botswana), Venesia (South Africa), and Catoca (Angola) sites in Africa. To continue mining operations, the AM-75 roadheader was delivered to the mine, which has the same modifications but has a lower capacity and dimensions. This roadheader has already been operated in the Far North at the Aikhal and Udachny mines. The authors were interested in the multimotor electric drive system of this complex and its energy performance.

The calculations resulted in the construction of load diagrams and static characteristics of a multimotor electric drive system of a mining roadheader using the methods of equivalent forces and reduced moments. Computer modeling was carried out, confirming the correctness of the calculations. Such studies are relevant for the global diamond-mining industry (Sedelnikova et al., 2019; Volotkovskaya et al., 2020). Based on the calculated equivalent forces, the preliminary and installation capacities of electric motors, which were subject to replacement due to failure, were obtained. Subsequently, three-phase asynchronous motors with a short-circuit rotor were selected from the available models. The equivalent force method is suitable for rotational mechanisms, showing a low absolute error between calculated and passport data, which is confirmed by computer modeling. The static characteristics of the selected electric motors were built on the basis of calculated reduced moments. These characteristics confirm the correctness of the motor selection. The calculations and computer modeling are useful for further computer simulation of the operation of electric drive systems of a mining roadheader and the power supply system of a mining site (Semenov et al., 2019a; Semenov et al., 2019b). In dangerous conditions such as underground mines, computer modeling is the only possible tool for further evaluation of power quality in the underground parts of the mine not accessible for experimental research and physical measurements (Semenov and Kuznetsov, 2014; Fedorov, 2017; Shpiganovich et al., 2017; Shevyrev et al., 2018).

The paper was funded by the Russian Scientific Foundation, project 21-79-20124 “Modeling of Electric Power Complexes and Systems Based on Theoretical and Experimental Research”.

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