Vol 35 Iss. 1

When automating mine load hoisting with asynchronous drive the main difficulties arise usually at the end of hoisting, when static resistances variable in magnitude and sometimes in sign are combined with low speeds.In order to obtain relatively rigid mechanical characteristics of the drive, necessary to ensure a stable low speed during the movement of lifting vessels in unloading curves, several methods have been proposed and partially tested in recent years.

Multi-dredge electric dredges are powerful floating units operating in placer deposits for mining gold, platinum and other minerals. The modes of operation of electric drives of the main mechanisms of the dredge are not studied sufficiently yet.In the present article as a result of analysis of the constructed and taken from nature load diagrams, a possible method of selection of the power of the main electric motor of the dredge - the motor of its scoop chain is offered.

The decisive requirement for the drive of single-bucket excavators is the creation of the optimal form of mechanical characteristic. Nowadays for excavators with bucket capacity 3-5 m³ the system of three-winding generator-motor TG-D has found application. The generator, having three excitation windings, creates a falling “excavator” characteristic. The drive is controlled by changing the current of the set winding 1. Negative one-stage current coupling - winding 3 - determines the falling form of the mechanical characteristic under overloads. Positive voltage coupling - winding 2 - provides high fill factor (0,7-0,8).

For the drives of electric motors are used asynchronous squirrel cage motors with a deep groove and double squirrel cage.The difference in the operation of electric motors of cutting machines is that they are included in the “non-rigid network”. At present the distance of the electric motor from the area transformer and the power of the electric motor itself are limited by the values of permissible voltage drops during operation and start-up of the electric motor.

As it is known, the load of downhole electric motors has a sharply variable character. When calculating the cable network should be based on the maximum performance of downhole machines and mechanisms. Therefore, the choice of the mode of calculation of the sectional cable network is especially important. For this purpose it is necessary to know the required voltage at different modes of operation of the main engine, which in the conditions of the coal mine site is the engine of the shearer or shearer machine.

In the socialist coal industry - one of the highly mechanized and electrified sectors of the national economy - the reduction of losses and savings of electrical energy can reach enormous proportions.Thus, for example, as a result of increasing the power factor by centralized compensation (artificially), as well as the removal of overestimated capacity of electric motors and transformers in the Ministry of Coal Industry in 1950 was saved 25.6 million kWh, and in 1952 - 74.4 million kWh of electricity.

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.

The Estonian oil shale deposit is characterized by large water inflows reaching 6000-8000 m3 / hour in spring floods (e.g. at the Käva II mine in April 1955). The geodetic height of water rise is small: 20-40 m - for the main drainage and 3- 4,5 m - for the area pumping.

As it is known, transient processes in the system under certain assumptions can be described by a linear differential equation. The order of the differential equation is determined by the number and nature of the links included in the system, since the differential equations of these links are the initial equations for the general equation of dynamics of the entire system.

The object of regulation in an electromechanical system is an electric machine - usually a motor or a generator.For automatic control and regulation of motor speed or generator voltage, closed-loop systems with negative feedback (regulating) are the most common. The main parameter of such a system, which determines its quality in steady-state modes, is the gain of the open-loop control circuit K, which is understood as the product of the gain (conversion) of all links of the control circuit. For example, for the system of electric machine control and motor speed regulation, the structural diagram of which is shown in Fig. 1, the gain of the open-loop regulation circuit is defined by the expression.