Tractor Wheel Research Articles

ДОСЛІДЖЕННЯ МЕТОДІВ ВИПРОБУВАНЬ ГІДРООБ’ЄМНОГО РУЛЬОВОГО КЕРУВАННЯ ТРАКТОРІВ

Abstract Purpose of the study. The purpose of the study is to increase the level of technical readiness of tractors based on indicators of the technical state of steering by improving the process of its diagnosis. In order to achieve the goal, it is necessary to substantiate the estimated indicators and develop a method of testing the hydrovolume steering of tractors using the method of partial accelerations. Research methods. The methodological basis of the work is the use of the method of partial accelerations. This method is based on the transition from the vector sum of forces in space to the vector sum of accelerations in space. This makes it possible to preserve the physical essence of the obtained vector equation describing the motion of the dynamic system. The method of partial accelerations, in contrast to classical methods, involves reducing the equations of dynamics to the equations of kinematics (principle of kinemodynamics). Further research is based on this principle. The results of the study. A method of testing hydraulic volumetric steering of tractors using the method of partial accelerations has been developed. The time of rotation of the tractor wheels from the extreme position to the extreme position is an indicator for diagnostics. It was established that the duration of turning the tractor wheels from the extreme position to the extreme position is correlated with the accelerations that occur in the front and rear half-frames of such a tractor. The rotation accelerations of the rear half-frame are more pronounced, compared to the accelerations of the front half-frame. This is explained by the different values of their mass index. Measurement of the indicator is possible using the method of partial accelerations. For this, measuring complexes based on accelerometers are used. Conclusion. The implementation of methods for assessing the quality of tractor steering units and the units developed according to the proposed methodology will allow for an accelerated assessment of their compliance with technical conditions and traffic safety during tests and in operation. The application of partial accelerations method makes it possible to make a conclusion about the technical condition of the elements and nodes of the hydraulic steering of the tractor without the presence of a special platform for running tests. As a diagnostic indicator, the longitudinal component of acceleration that occurs when the guide wheels turn is proposed. The labor intensity of tests using this method is reduced by 3.28 times compared to the known ones, and the consumption of working fluid is also reduced by 2.7 kg, as the operation of disassembling units is eliminated. Key words: tractor, hydraulic power steering, test, turning time, condition indicator, method.

Efficiency coefficient of tractor wheel drive while moving on ground

Purpose. The purpose of the study is to improve the energy efficiency of tractors when working on a deformable support surface by increasing the efficiency of the wheel drive due to the rational selection of its parameters. Methods. The methods of the theory of movement of traction vehicles and theoretical mechanics are used. Results. Analytical equations are compiled that describe the dependence of the interaction of wheels with pneumatic tires with the ground support surface. The effect of tangential soil compliance on the efficiency of a single wheel and wheel drive was determined, and the influence of soil compliance was taken into account to determine the rational distribution of torque (traction) moments between the driving axles of a two-axle tractor. Conclusions 1. As a result of the conducted research, the dependence of the coefficient of useful action of the tractor's wheel drive on the coefficient of distribution of torque (traction) moments between the axles during movement on a deformable support surface was determined. The resulting mathematical model takes into account both the circular stiffness of the tires of the driving wheels and the flexibility of the soil in the contact patch. 2. The rational (optimal with the adopted mathematical model) value of the torque distribution coefficient βm between the axles should vary depending on the rolling resistance of the driving wheels and the characteristics of the soil background. With an electric drive of the driving wheels, adjustment of the coefficient βm is possible, and with a mechanical drive of the driving wheels, control of the coefficient βm can be carried out by adjusting the ratio of torsional stiffnesses of the tires of the front and rear wheels due to their internal pressure. 3. For agricultural tractors it is advisable to adjust the air pressure in the tires for each bridge separately, depending on the type of running system(4K4a, 4K4b) and the physical condition of the soil. Keywords: wheel drive, two-axle tractor, coefficient of useful action, deformation of the support surface, traction moments.

A method for analysing the lateral stability of wheeled farm tractors by obstacles on slopes

A method for analysing the lateral stability of wheeled farm tractors by obstacles on slopes

Expanding the technological capabilities of the integral tractor chassis by reversing the transmission

The aim of the work is to find technical solutions that provide a complete reversal of the transmission on the example of an integral tractor, while allowing maximum use of commercially available units or installed as an option for a serial machine. The objects of study are mainly the chassis of a wheeled integral tractor designed for agriculture. The relevance of creating fully reversible transmissions for integral tractors and other agricultural, road-building and transport machines is shown. The variants of installation places for the reverse gear are considered, the features of loading and the principles of designing the reverse gear for specific placement points are analyzed. The most promising options for the case of an integral tractor based on a serially produced chassis were chosen - placement of a controlled power distribution mechanism in the rear axle gear housing or instead of wheel gears. Kinematic schemes and a technique for determining gear ratios and kinematic parameters are proposed. The reverse gear control technologies and the technological base for the design and manufacture of such mechanisms are indicated: when designing an integral tractor in accordance with the principle of maximum unification with a serial chassis, it is advisable to place the reverse gear in the drive axle housing; when developing an original reverse transmission and a new carrier system, the reverse gear should be located in front of the gearbox; in the design of the reverse gear, it is preferable not to use a blocking clutch, replacing it with a planetary gear set and a brake.

A method for analysing the lateral stability of wheeled farm tractors by obstacles on slopes

In order to study the influence of speed, slope angle and ground adhesion coefficient on wheeled farm tractor lateral stability, this paper proposes a dynamic mechanical lateral stability of wheeled farm tractor model caused by road obstacles on slope. The model constructs the stability evaluation indexes to judge the stability of the farm tractor. The geometric size and mass of JIN-MA300 farm tractor are used to analyse and calculate the stability of the farm tractor. The analysis shows that the height of obstacles on the slope and the speed of the farm tractor are proportional to the farm tractor rollover index (TRI); the farm tractor sideslip index (TSI) decreases with the increase of speed. The TRI and TSI are calculated at different obstacle heights and vehicle speeds. The results reveal that both TRI and TSI increase with the obstacle height; the vehicle speed has a great influence on TRI.

Ensuring the stability of the suspended chisel-cultivator processing depth

The depth of tillage and its uniformity are the main performance indicators of chisel cultivators, as well as all tillage machines. Only when these indicators are at the level of demand, favorable conditions are created for the uniform development and ripening of crops throughout the field and their high yield. The article theoretically explores the problem of ensuring a smooth movement of the suspension chisel cultivator along with the working depth. The results show that the given depth of tillage and its uniformity at the required level is mainly due to the correct selection of the vertical distance from the base plain of the chisel-cultivator to the lower hanging points. The vertical distance from the base plain to the lower hanging points must be at least 48.1 cm in order for the condition N>0 to be fulfilled and the chisel-cultivator to sink to the specified depth and run steadily at this depth. Suspended chisel-cultivators with 3-4 class wheeled tractors, which are widely used in agricultural production of the republic, the vertical distance from the base plains to the lower hanging points. Determined to be at least 48.1 cm.

Investigation and substantiation of the parameters of the plow body angle lift

Currently plowing fields from under various agricultural crops is carried out with reverse plows in Uzbekistan. Their use can dramatically reduce labor and money costs for conducting current and capital field planning. With the supply of energy-rich wheeled tractors to the Republic of Uzbekistan, one of the most effective ways to increase the productivity of plowing units at present is to increase the plow's working width by increasing the number of housings. Increasing the number of hulls on revolving ploughs, equipped with pre-ploughs, this leads to a sharp increase in the metal and energy consumption of ploughs, since the latter have a double number of working elements. Therefore, an important role is played by the optimal placement of plow bodies along the plow course and the maximum reduction of distances between them, when using angle plates on the bodies instead of traditional pre-plows. The article discusses experimental influence of the angle-lift radius of curvature, the installation height, and the installation angles in the longitudinally-vertical and transversely-vertical planes on the traction resistance of the hull and the depth of embedding of plant remains was studied by MRI.

РАЗРАБОТКА МОДЕЛИ СЕЛЬСКОХОЗЯЙСТВЕННОГО ТЕХНОЛОГИЧЕСКОГО МОДУЛЬНОГО АГРЕГАТА НА ОСНОВЕ ПОЛНОПРИВОДНОГО КОЛЁСНОГО ТРАКТОРА

The modular structure of an agricultural technological unit, consisting of an energy-saturated wheeled tractor, aggregated by a trailer with an individual drive of the leading propellers and a technological machine (disk harrow) when performing agrotechnological operations, is con-sidered, using the example of tillage with disks. A mathematical model of the transmission of a four-wheel drive tractor in combination with a trailer equipped with an individual drive of propellers is presented. A possible algorithm for the control system of this unit is described. A general structural model of an agricultural technological unit is proposed.

Warning and active steering rollover prevention control for agricultural wheeled tractor.

Tractor rollover is regarded as the most fatal incident in agricultural production, but some of which can be avoided by timely anti-rollover warning and active control. There have been a lot of researches on the tractor rollover model building and rollover protective structure designing but few on the anti-rollover control. The purpose of this study is to develop a cheaper and practical anti-rollover control system based on active steering technique and to prove the efficiency of the proposed scheme for the wheeled tractors. A three-degree-of-freedom rollover dynamics model including automatic steering system is established. A control scheme by adjusting the roll angle to keep the stability based on the adaptive sliding mode control is proposed with the estimated lateral velocity according to the feedback correction principle. Front wheel angle tracking controller is designed adopting internal model control (IMC) theory. Simulation results exhibit that the active anti-rollover control can calculate the stability index in real time and can keep it within the stable range by adjusting the front steering wheel angle. It is prospective for the proposed scheme to provide a valuable reference to reduce tractor rollover accidents.

DESIGN FEATURES OF MODERN FOREIGN AGRICULTURAL TRACTORS

Analysis of the state and trends in the development of agricultural machines and the technical means that serve them shows that there is a constant process of creating more productive and economical equipment. This is primarily ensured by increasing unit capacity, increasing working and transport speeds, reducing time losses for auxiliary operations, reducing maintenance costs to a minimum; ensuring minimal impact on soil and plants; increasing reliability and wear resistance, as well as an increase in versatility and the appearance of special tractors for specific work; expansion of production of wheeled tractors with four driving wheels, wider use of hydraulic systems, electronics, automation, new materials, creation of comfortable working conditions and ease of management; ensuring labor safety. The main type of tractor in the most widespread range of capacities remains the wheeled one of the traditional layout scheme, the improvement of which is carried out taking into account the latest achievements of science and technology. There is a further update of articulated tractors with all driving wheels of the same size, with leading manufacturers experimenting with the installation of triangular track drives instead of wheels, which significantly increases their traction qualities. Characteristic features of tractors of the new generation are their universality and block-modular structure. So, depending on the market, different engines from well-known companies and unified transmissions are installed on one model of European tractors. Therefore, in this market, there is a tendency for manufacturers to cooperate with the aim of further increasing versatility, reliability, and simplifying operation: increasing the interval for changing engine oil to 500 hours, transmission oil to 2,000 hours, hydraulic oil to 1,000 hours. Cooperation also contributes to the expansion of opportunities for competition in the markets of different countries. The new generation of powerful wheeled tractors with a classic and system layout provides high efficiency mainly in technological operations with medium traction forces in combined, tillage and sowing units, which are equipped with implements with active working bodies, with front and rear GDP, as well as in transport operations.

Development of low-cost self-propelled multi-purpose power unit

The self-propelled multipurpose power unit was developed in the laboratory of Farm Machinery and Power Engineering, JNKVV, Jabalpur for small farmers. The prime mower is powered by a 5hp diesel engine. The V-belt drive is provided for the transmission of power from the engine to the traction wheels. An adjustable accelerator wire is connected to the governor for adjusting the engine speed according to the requirement. The worm gear reduction unit is located at the axle having a speed reduction ratio of 20:1. A telescopic type frame is provided to support the end of the adjustable output shaft with the help of a bearing. The handle is modified to vary the height from 1.0 to 1.3 m from the ground. The additional lug cage wheel is connected to the transport wheel to increase the traction. Noise and Vibration isolators are provided between the engine and chassis to reduce the noise level and vibration. The noise level of the power unit was suitable for 8 working hr. The range of noise with load conditions is 60, 65, 70 (dB) and without load conditions 74, 79, 86 (dB), this limit of noise is under the permissible limit 90db. Vibration range according to optimum rpm 1200, rated rpm 1500 and maximum rpm 1800 so the output range of vibration in Handle 130 μm and chassis 217 μm, Handle 127 μm and chassis 198 μm, Handle 121 μm and chassis 193 μm.

Теоретичне дослідження умов максимально допустимого буксування рушіїв колісних енергетичних засобів

Goal. Determination of the maximum allowable skidding of wheel drives, provided there is no cut and the manifestation of such a level of its displacement by the tire grips, which does not exceed the specified strength limit. Methods. Are based on the use of sections of the theory of traction dynamics of a tractor, which consider the rolling process of an elastic traction wheel on a deformed soil surface. Theoretical calculations of the obtained analytical regularities were carried out in the MathCad 15.0 software environment. The initial data were the parameters of the typical soil environment of the south of Ukraine and the design parameters of tractors of traction classes 1.4 and 3, which are most common in this area. Results. An analytical dependence has been developed that allows you to determine the maximum permissible level of skidding of wheeled power vehicles, taking into account the shear strength limit of the soil medium. According to the calculations, it was established that the maximum allowable value of wheel drive towing significantly depends on the condition of the agrotechnical background on which the tractor moves. A quantitative characteristic of this condition is the coefficient of rolling resistance of the wheel drive. No less significant influence on the value of the maximum permissible skidding of the drivers of wheeled power vehicles is exerted by the angle of the position of the ground grip on the tire in relation to its longitudinal axis of symmetry. Conclusions. Theoretical studies have established that the greater the coefficient of rolling resistance of a wheeled vehicle on this or that agrotechnical background, the smaller the maximum permissible value of its skidding should be, with a more economical impact on the soil environment. Compared to a tractor of traction class 1.4 (MTZ-892), the use of a power tool of traction class 3 (XTZ-17221) is possible with higher values of the maximum permissible towing. The results of mathematical modeling prove that with an increase in the value of the angle of placement (inclination) of the ground grip to the longitudinal axis of symmetry of the wheel drive, the maximum permissible level of its skidding should be lower.

To the issue about the tractional passability of high-clearance completely-driven four-wheeled universal-row cotton crop tractor

The results of researches implemented in the sphere of improving the agrotechnical passability of 4-wheeled universal-row cotton crop tractor are specified in the article. Replacing these two types of wheeled tractors with one high-clearance 4-wheeled tractor significantly reduces the range of fleet and increases the annual load of universal-row crop tractor of 1.4 class, and finally, increases the efficiency of their applying. The weight distribution of perspective four-wheeled universal-row crop tractor onto four wheels and fully drive reduces the negative impact on soil in comparison with three-wheeled tractor and allows to aggregate machines having enlargedrow-spacings. Evaluation of P indicator (the passability margin) is shown. It characterizes the passability through more problematic matters due to traction-coupling properties presowing soil processing proceedings, which showed the possibility of applying the tractor as well at all remaining operations, provided for by the technological map and being performed by the units on the base of this tractor.

ВИЗНАЧЕННЯ ЗОВНІШНІХ ШВИДКІСНИХ ХАРАКТЕРИСТИК СИЛОВОГО ОБЛАДНАННЯ ДОРОЖНІХ МАШИН

The paper deals with the issue of determining the fuel efficiency and toxicity of exhaust gases of power equipment of road machines operating in traction modes, namely, plow and plow-brush snowplows based on a pneumatic wheeled tractor. The object of research is fuel efficiency and toxicity of exhaust gases of power equipment. The purpose of the study is to experimentally determine the external speed characteristics of a 4Ч11,0 / 12,5 diesel engine (D-240, D-241, D-242, D-243 families), namely: maximum power Ne, maximum torque Mк; hourly consumption of fuel Gпал and air Gпов, specific effective fuel consumption ge; concentrations of harmful substances in the exhaust gases: carbon monoxide CO, hydrocarbon compounds CmHn, nitrogen oxides NOx and opacity N of the exhaust gases. The paper presents the results of experimental studies to determine the energy performance (maximum power Ne and maximum torque Mк) of a diesel engine (4Ч11,0/12,5 (D-242)) of power equipment; fuel efficiency indicators (hourly fuel consumption Gпал and specific effective fuel consumption ge); hourly air consumption Gпов; concentrations of harmful substances in the exhaust gases: carbon monoxide CO, hydrocarbon compounds CmHn, nitrogen oxides NOx and opacity N of the exhaust gases. Which are obtained with the position of the fuel supply control, which corresponds to the maximum fuel supply from the diesel crankshaft speed. The above indicators were determined at standard diesel fuel supply settings. Based on the obtained external speed characteristics Ne, Mк, Gпал, ge, Gпов, CO, CmHn, NOx and N, mathematical (polynomial) dependencies were determined, which are described from the speed of the diesel crankshaft, and their adequacy was checked. The studies carried out made it possible to determine the main direction of increasing fuel efficiency and reducing emissions of harmful substances of a diesel engine.

A joint control method considering travel speed and slip for reducing energy consumption of rear wheel independent drive electric tractor in ploughing

Improving tractor traction efficiency is greatly important in increasing energy efficiency and reducing fossil fuel consumption. However, the wheeled tractors have problems with low traction energy efficiency and severe energy consumption due to excessive wheel slip in ploughing. This paper proposed a joint control method considering the travel speed and slip based on the active torque distribution, which is applied to the independent drive electric tractors. Considering the influence factors of time-varying resistance and terrain elevation in ploughing, a time-varying dynamical model for the tractor-implement combination was established to reveal the load transfer rules. Then the optimal slip values of the driving wheels were solved in real-time, and a sliding mode algorithm was used to control the motor torque for efficient tractor operation. Moreover, a hardware-in-the-loop platform was built, and ploughing tests were performed. The results indicated that the tractor slip, traction energy efficiency and motor energy consumption of the tractor were optimal in the torque active distribution mode. Compared to the torque average distribution mode, the proposed method reduced the tractor slip by 14.1%, the motor energy consumption by 6.8% and increased the traction energy efficiency by 6.8%. This study provided technical support for reducing energy dissipation in ploughing.

Mathematical simulation of the automatic control of the tractor power unit

BACKGROUND: Many manufacturers of agricultural tractors have machines with automatic gearboxes in their product line. The development of the design of this type of transmissions, the control system and the algorithm of its operation is an urgent technical task.
 The article considers the issues of mathematical simulation of the working process of the automatic transmission of a wheeled tractor and the automatic transmission control system.
 AIMS: The purpose of the work was to determine the optimal control laws of automatic control of a wheeled agricultural tractor engine and transmission in various operating modes using a digital model of the tractor transmission.
 METHODS: Simulation of working conditions is performed in the Matlab program digital software packages and its applications Simulink, Simscape. At the same time, with the help of fundamental data blocks of these applications, models of the physical components of the gearbox and the machine engine and the tractor power transmission control system, are created.
 RESULTS: The application procedure of the MATLabSimulink, Simscape software package for mathematical modeling of transmission operation control is considered. With the help of the developed mathematical model, a simulation of the tractor power unit operation in the main operating modes was carried out in order to optimize the characteristics of the tractor control system.
 The scientific novelty of the research lies in the selection and optimization of the transmission control laws in accordance with the requirements to agricultural tractors with an automatic step gearbox.
 CONCLUSION: The practical utility (value) of the research lies in the possibility of using the proposed control laws to develop a transmission control system for new tractors with an automatic step gearbox.

Technological employment of fire-fighting adapter to increase the efficiency of extinguishing forest fires

Abstract The paper presents the results of the solution defining the possible application of the adapter as a fire-fighting mobile device with a base machine of a forest wheeled skidder (LKT) in the fire protection of forests in the Slovak Republic. Following the challenging accessibility to fire-fighting machinery during any intervention in forestry operation, the main aim was formulated. It will be about basic technical parameters of the DATEFF fire-fighting adapter, resulting from operational measures and following specification of its tactical deployment in extinguishing forest fires. This fact also follows from based on statistically processed data on fire in state forests of the Slovak Republic in the last ten years. The greatest damage occurs mainly the forests at a slope gradient of 16%. Designed fire adapter is structurally designed mainly to these terrains. Regarding its design and technical parameters, the proposed DATEFF adapter can be employed tactically as fire-fighting mobile device. In the case of an unavailable water source without access to the forest transport network, the adapter can be used as a part of long-distance water transport or as a mobile device for emergency import of material. Another option is to use it as a water tank in inaccessible terrain with the possibility of refilling using a Bambi bag and a helicopter. This fire-fighting adapter DATEFF is designed for forest wheel tractors that reach 40% slope availability, are able to work on the stand area, overcome obstacles and are available in sufficient quantities in all Slovak forest owners.

Transfer Case Clutch Torque Estimation Using an Extended Kalman Filter With Unknown Input

Vehicle wheel traction forces play an important role in vehicle performance, especially for four-wheel-drive vehicles, where a transfer case clutch is used to distribute torque between front and rear wheels. Due to lack of production ready low-cost torque sensor, the transfer case clutch torque is not measured and needs to be estimated accurately to optimize vehicle traction performance. This article proposes to estimate the transfer case clutch torque by forming an estimation problem with unknown system input(s). Specifically, a unified clutch torque estimation model is developed for different clutch conditions, where overtaken-clutch case is treated as a special case of slip-clutch condition with slip-speed equals to zero. Note that under overtaken condition, the associated system model with only one known input is different from that under slip condition with two known inputs. A real-time implementable recursive solution for unknown input(s) is obtained by utilizing an unknown input observer based on the extended Kalman filter (EKF-UIO) algorithm. Comparing with the existing direct estimation method and experimental measured data, it is found that the proposed EKF-UIO algorithm is able to reduce both absolute mean square error and relative-mean-square error significantly with respect to the measured clutch torque under both slip and overtaken conditions. In summary, the EKF-UIO estimation algorithm based on the unified clutch torque model is able to estimate clutch torque accurately.

Experimental investigation of tire traction performance on granular terrain

In this work, an indoor soil bin traction measurement system is developed to systematically investigate the traction behavior of an off-road tire in interaction with granular terrain. The system is composed of a soil bin, a single wheel test device, a soil mixing/compaction device and its control and data acquisition system. Then the traction performance parameters such as the wheel traction force, sinkage, soil deformation and/or failure mechanism are obtained and investigated by using the system under different working conditions (tire slip, wheel load, tread pattern, granular medium). The experimental results show that the wheel traction force and sinkage present high linear correlation with the tire slip and wheel load. The wheel traction force and sinkage are also found to be directly influenced by the tire tread patterns and granular media. Moreover, with the increase of slip, the shear failure of the soil terrain behind and under the tire becomes more obvious, and the ruts become more blurred. The trend of shear failure mode of the granular terrain from local shear failure to overall failure is becoming ever more obvious. However, under the same tire slip, the wheel loads (7663 N, 10163 N and 12663 N) have little effect on the failure mode of soil terrain. Finally, the experiments indicate that the trafficability of the off-road tires on the gravel terrain is better than that on the sand terrain. The traction performance of the groove tires under the same soil conditions is better than that of the smooth tires.

Теоретичне дослідження коливальних рухів гичкозбиральної машини, встановленої спереду агрегатуючого трактора

Goal. To increase the quality of gathering and reliability of the top-gathering machine by minimizing the amplitude of its angular oscillations during movement on the unevenness of the soil surface. Methods. Theoretical studies were carried out using the basic principles of higher mathematics and theoretical mechanics, in particular the dynamics of a mechanical system. Numerical calculations and graphical dependences were obtained using a PC with the help of the developed and standard programs. Experimental studies were carried out according to standard methods of field multivariate experiments. Results. Based on the developed equivalent scheme of the frontally attached to the wheeled tractor top-gathering machine, the differential equation of the angular oscillations of the top-gathering machine to the center of instantaneous rotation of the tractor attachment mechanism was compiled. The analytical solution of this equation was obtained thanks to the law of oscillatory motion of the top-gathering machine in the longitudinal-vertical plane. As a result of numerical calculations, graphical dependences were built of the angle of rotation of the top-gathering machine at different speeds of its translational movement and different values of the coefficient of stiffness and damping of the tires of the copying wheels, as well as at different values of the main design parameters of the machine and the step of the unevenness of the soil surface. Conclusions. To reduce the amplitude of the angular oscillations of the harvester in the longitudinal vertical plane, its supporting wheels should be located as far as possible from the instantaneous center of rotation of the tractor’s front attachment mechanism. The central thrust of this mechanism should also be installed at the greatest possible angle of inclination to the vertical. The greater the step of the unevenness of the soil surface, the more stable will be the movement of the front-mounted top-gathering machine in the longitudinal-vertical plane. According to experimental studies, with amplitudes of oscillations of the lower ends of the knives of the rotary cutting device up to 5 cm, the loss of the sliver is insignificant. However, when the amplitude of these fluctuations increases to 7 cm or more, these losses become more significant and their maximum values can reach more than 12%.