Lift automation at skips with bottom unloading in the period of deceleration can be realized by application of dynamic braking mode of asynchronous lifting motor. In Fig. 1 the calculated diagram of velocity during the deceleration period t₃ is shown by the dotted line λr. During the unloading period t₄', a constant velocity v₃ (line ρϕ) is assumed, which drops to zero during the period t₄ along the line ϕф. According to the force diagram of the induction machine shown in Fig. 2, the acceleration of the hoisting motor during the start-up period occurs along the broken line BCDEFGHIKLT, varying about the given (design) force value F₁ as about the average value between the extreme limits F₁' and F₁". At the end of the start-up period, there is a full stroke period during which the driving force follows all changes in the static force. Assuming a statically unbalanced lifting system, let the static force, and hence the driving force developed by a motor operating on the natural characteristic R₂, vary from the value of F's₂ at the beginning of the full stroke period (point N') to the value of F"s₂ at the end of this period (point N). At the end of the full stroke period, there comes a deceleration period t₃, during which a braking mode is assumed, which is implemented in the form of dynamic braking. An asynchronous machine from the motor mode on characteristic R₂ at speed vₙ is switched to dynamic mode by switching the stator from alternating current to direct current.

The dynamic braking system has recently become widely used in coal mines for inclined lifts in cases where it is necessary to lower cargo or people at reduced speed. Compared to the counter-current mode, dynamic braking is more economical. In appropriate cases, dynamic braking can also be used for vertical lifts.

In practice, it may be necessary to lower people down a mine shaft at a reduced speed compared to the full speed of lifting the load. This makes it necessary to use braking operations, which in practice are often carried out using a mechanical brake. However, prolonged operation of a mechanical brake is accompanied by undesirable phenomena: excessive heating and wear of the brake pads, which necessitates the use of cooling devices and frequent replacement of worn pads with new ones. Electric braking systems are free from these drawbacks, of which in the case under consideration both counter-current (counter-switching) and dynamic braking can be used. To be able to implement the counter-current mode, the lifting unit must be equipped with a load rheostat, which, compared to an ordinary starting rheostat, must be designed for longer operation. In addition, this rheostat must have additional sections with a correspondingly increased resistance to be able to obtain small braking moments. The main disadvantage of counter-current braking is its uneconomical nature, due to the significant consumption of energy from the network. As is known, the power consumed in the counter-current mode from the network depends on the magnitude of the braking torque and synchronous speed and does not depend on the actual speed of descent. The energy consumed from the network is inversely related to the speed of descent.

For the proper functioning of the lifting unit, first of all, the correct operation of the main bearing lubrication must be ensured, which is carried out using two oil pumps, one of which is working and the other is a spare. The oil pumps are controlled using the oil pump switch. After the circuit of the coil 1RP is closed, its contact 1RP will close and thereby bypass the contact KK-0, which is open in the working positions of the command controller, ensuring the closure of the circuit of the coil 1RP until this circuit is broken by the limit switch ZVK, which is opened at the end of the lifting by the corresponding cage. When the circuit of the coil of the relay 1RP is closed, the contact of this relay 1RP, which is in the circuit of the coils of the reversing contactors B and I, will be closed. As a result, the circuit of the coils of the said reversing contactors will be closed at this point.

The idea of applying an electro‑hydraulic drive to mine hoisting occurred to the author of this article in 1944. To implement it, at the author's suggestion and under his scientific supervision, research work was organized in 1945 at the Leningrad Mining Institute, with the participation of Associate Professor A. E. Maksimov as principal investigator. After obtaining theoretical and experimental results, the first electro‑hydraulic hoisting machine in mining practice was built in 1947 through the joint efforts of researchers from the Department of Mining Electrical Engineering of the Leningrad Mining Institute and a group of engineers. The operating principle of the electro‑hydraulic drive is as follows. Between a continuously rotating electric motor and the working machine – in this case, the hoisting machine – a hydraulic link is inserted: a centrifugal fluid coupling. Thanks to this, depending on the degree to which the fluid coupling is filled with working fluid, it becomes possible to obtain various hoisting speeds, from zero to maximum.

The author examines in detail 1) centrifugal fans: fan drive systems, fan control of electric drive units; 2) axial fans, fan drive systems and electric drive control of fan units.

In the section concerning the actuator, machines with a constant winding radius are considered, as they have received preferential distribution in the USSR. Along with the kinematics and dynamics of hoisting with ordinary cages, considerable attention is paid to hoisting with tipping vessels and skips with bottom unloading. It is necessary to note that when considering various hoisting modes, in some cases, instead of the corresponding references, some formulas are repeated, which serve to determine the forces and powers in similar conditions, while maintaining, however, the identity of the numbering of the said formulas. Such a system of presentation allows for more convenient calculations for the corresponding hoisting modes, without having to search for the necessary expressions in different places in the book. A special section of the book is devoted to the consideration of the kinematics and dynamics of lowering with three-period tachograms carried out during operation by ordinary cages. With regard to the drive and control of the hoisting machine, a study was made of the physics of the processes occurring in various hoisting modes, both simple and the most complex, based on the coordination of the kinematics and dynamics of hoisting with the mechanical characteristics of the hoisting motors of both systems, i.e. asynchronous and in the Leonard drive. The calculation side, illustrated with numerical examples, relates to the definition of elements of the kinematics and dynamics of hoisting, energy consumption for hoisting, efficiency of hoisting units, starting rotor resistances of asynchronous hoisting motors and acceleration relay settings during automation of the starting period, the power of the hoisting motors, as well as the power of individual machines that make up the converter unit in the Leonard system. In conclusion, it should be noted that the issues considered in the proposed work, which is the result of many years of research by the author in the field of electric mine hoisting, are presented mainly in his own original interpretation. F. Shklyarskii June 1943

November 2, 1944 marked the 70th anniversary of the birth of one of the foremost specialists in the field of mining mechanics, Academician Alexander Petrovich German.

The initial data for calculating the starting resistances are the following quantities: 1.Power and type of the drive motor; for the latter, the following must be obtained from catalogues: a) the ratio of the breakdown (maximum) torque to the rated torque; b) the rated rotor voltage; c) the rated rotor current; d) the efficiency of the motor; e) the synchronous and rated rotational speeds of the motor; 2. Calculated values of the starting torque; 3. Values of the static resistance torques corresponding to the starting period; 4. Number of steps of the rotor rheostat; 5. The starting period t1 and the entire period of the working cycle T, including the pause θ, in accordance with the given speed diagram (Fig. 1). The basis for calculating the starting resistances should be the mechanical characteristics of the motors, which must be constructed in advance (Fig. 2). In this context, one very important condition must be noted: not every motor of a given power rating will be able to meet the required starting conditions with a predetermined number of steps in the starting rheostat circuit, because the necessary range of variation of the starting torque cannot be maintained for just any magnitude of the motor's breakdown torque. To finally determine the individual steps of the rheostat, it is necessary first to determine the required operating time for each step, i.e., the duration during which one step is energized, as well as the magnitude of this current.

Starting a synchronous motor may be performed both with full voltage and lowered voltage. Fig. 1 shows a principal scheme of connecting a synchronous motor whose starting is performed under full voltage; principal schemes of connecting synchronous motors whose starting is performed under lowered voltage are represented in Fig. 2 and 3, respectively for cases of starting by means of a reactor and autotransformer. The present paper examines automatic control operations in compressor plants driven by synchronous motors whose starting is performed under full voltage; automatic protection of these plants from treating troubles is also considered. A method of starting synchronous motors under full voltage being the simplest both in its operations and with regard to its starting equipment is likely to be extensively adopted in next future in the mines of USSR where stations and substations under certain conditions of their capacity will admit of directly connecting powerful compressor plants served by synchronous motors.

As is known, a completely accurate determination of the individual parameters of a three-period tachogram of mine hoisting occurs when the tachogram is a trapezoid with straight sides. Below are proposed precise methods for determining the tachogram elements for two hoisting systems, given straight sides for the acceleration period t1 and corresponding curved sides for the deceleration period t2. Precise determination of the individual elements of the three-period tachogram is possible: 1) when its sides corresponding to the acceleration and deceleration periods are straight; 2) when one side corresponding to the acceleration period is straight and the other side corresponding to the deceleration period is curved according to a sine or hyperbolic sine law, provided that the acceleration period t1 is the unknown quantity. In the article are proposed exact methods for determining the elements of the tachogram for the two hoisting systems mentioned above, given the presence of straight-line segments for the starting period t1 and corresponding curved segments for the deceleration period t2. In practice, such tachograms can be used as design ones for the case of an asynchronous hoist motor, with contactor control employing appropriately adjusted time relays.

The use of a motor-generator set with a flywheel (Ward-Leonard-Ilgner) as the main drive of a synchronous motor is dictated by the presence of a hydraulic coupling connecting the shaft of the main motor to the shaft on which the alternating voltage is located. The dynamo and the flywheel are mounted on the latter. This coupling replaces the automatic slip regulator of the flywheel, which operates at a constant speed of the synchronous main motor. This article describes the installation of the hydraulic coupling and the concept of its use in the Ward-Leonard-Ilgner system with a synchronous main motor.