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circuit to which the output is usually connected normalizing amplifier NA and display device information DDI.
The output voltage of a bridge measuring circuit can be represented as:
K
UBHX = UM (K + s , (l)
where: £ — relative change in resistance R1 shoulder; K = R3/R4 — bridge coefficient symmetry; UM — voltage bridge circuit. Values of £ is determined from the formula:
1 + g q«c L - q«c
1 + - q«c - q«c
-1
(2)
where: q — heat flux; H — level full range of level changes; h — the current level; gx, gr — respectively the heat transfer coefficients of the wire in a liquid medium and gas; a0 — temperature coefficient of resistance of the wire material.
Analysis ofthe expression (1), (2) and the graph in Fig. 3. Show that for small values of e static characteristic linear enough.
Studies have also shown that the development level of thermal converters for hydraulic systems, it is advisable to perform them on the basis of the basic modular structure (see. Fig. 2), represents the dielectric nonconductor cylindrical rod, the entire length is a definite step wound copper wire with resistance R and R2 heat level converter. This design is placed in a perforated protective cover [4].
Fig. 3. Static characteristic heat level converter The developed design of the thermal water level converter has been tested during the monitoring and control of water level in the vertical drainage wells [5]. Maximum measurement depth reached 6 m; error of not more than 0.5 % of the upper limit; power consumption 10 W.; the water temperature is 5 °C - 25 °C.
It should be noted that the proposed liquid level gauge has a simple structure, fabrication of the device does not require high material costs. A distinctive feature of the transmitter is reliability, for its operation does not require special training of the staff.
References:
1. Ташматов Х. К. Устройство и приборы для регистрации максимальных и минимальных уровней воды в гидроузлах//Молодой ученый. - 2016. - № 2. - С. 238-241.
2. А. С. № 315945 Тепломанометрический уровнемер жидкости/Р. К. Азимов, Е. И. Гуревич, Е. А. Соколовский и В. С. Андрю-щенко//Опубл 01.10.1971. Бюл. № 29.
3. Ташматов Х. К. Тепловой преобразователь уровня воды//Датчики и системы. - 2006. - № 3. - С. 41-42.
4. Патент UZ. №IAP 04560. Тепловой преобразователь уровня жидкости/Ташматов Х. К., Азимов Р. К., Маматкулов Д. А.//Опубл. 2012. Бюл. № 8.
5. Tashmatov X. K. Heat liquid level sensor//European applied science. - 2016. - № 1. - P. 64-68.
ь
Kamalov Tolyagan Sirajiddinovich, Doctor of Technical Sciences, Professorr Institute of Power Engineering and Automation of the Academy of Science of Uzbekistan E-mail: tkamalov@yandex.ru Toirov Olimjon Zuvurovich, Ph. D., Senior Researcher, Institute of Power Engineering and Automation of the Academy of Science of Uzbekistan E-mail: olimjon.t@mail.ru
The method of determining the energy-efficiency of career excavators of the mining industry
Abstract: The composition of electrical equipment is determined, taking into account the efficiency of the constituting participating in the execution of each operation a complete cycle of operation (pressure, lifting, turn taking into account the reverse and move) for career excavators. A method of calculating the power consumption of career excavator calculation and analytical methods based on given values of the efficiency of each component of the electrical equipment and machinery in general is developed with the known value of their efficiency and power consumption of the actuating mechanism (pressure, lifting, turn taking into account the reverse and move). Calculation-experimental method is based on measurement results of
electrical energy consumption of each component of the operations of a single cycle of operation excavator or the total consumption of electrical energy for a certain period of time (hours).
Keywords: excavator, power consumption, specific norm, calculation and experimental method.
Introduction
The careers of the mining industry the main technological equipment are the drilling rigs and excavators, from which the power-consuming equipment are single-bucket excavators and the effectiveness of the use of their depends essentially the work of the mining enterprise. Excavator career tracked (ECT) is a full-circle electric a direct shovel on crawlers. It is intended for excavation and loading in transport of the heavy rock previously loosened by the explosion. Career excavators ECT are issued with ladles from 4 up to 46 m 3. To the main mechanisms include those that are directly involved in the process of excavating the ground: lifting, turning, pressure.
The main indicator of work of excavators is their power consumption and reliability. Development of the power equipment and decrease in consumption of active energy compared with traditional systems devoted the works [1-4].
The full cycle of work of a excavator includes following technological operations: digging, lifting laden bucket, platform turn to the place of an unloading or lifting of laden bucket with simultaneous turn of a platform to an unloading place, opening bucket — unloading and returning, turn of the empty bucket in the face, in addition, through a certain time interval moving — a move excavator.
One of the main energy indicators of any installation, including mining excavators is the specific power consumption (consumption of electrical energy for one full cycle of operation of the excavator by one meter of a cube mass of ore).
Methods of Research
The specific consumption of electrical energy can be calculated by two methods: calculation-analytical and calculation-experimental.
The calculation-analytical method — is based on the definition of productivity of a excavator and consumption of electrical energy theoretically. Under the productivity of the excavator is understood as volume of the rock, separated from the array and an excavator moved by a predetermined distance determined by its operating parameters in a unit time. On the productivity of the machine is affect by such factors as the mining and geological, constructive, technological, climatic, organizational [4].
Theoretical productivity of an excavator is quantity of rock mass (in tons or cubic meters) which can be recycled in unit of time. Hour, shift, days, month or year is accepted to a time unit. Thus the resistivity of rocks digging Kr accepts the maximum allowable under the passport of the machine; coefficients of filling of bucket K and loosening of rocks K — equal to one; angle of rotation on unloading in career of the excavator — 90°, height digging of bucket — at the level of an axis of the pressure of shaft of the stick H; the speed of working of movement shall be established by nominal (on the passport).
Theoretic productivity of the career excavator on the crumbling mass is determined (in cubic meters per hour) by the formula [4]
qt =3600•E, (1)
where E — capacity installed on an excavator of bucket (standard or changeable), m 3;
T — duration of a cycle of work of the machine (indicated in the technical characteristic of an excavator for angle of turn of boom on unloading, equal 90 °), sek.
For the angles of turn distinct from 90 °, cycle time is multiplied by the reduced correction coefficient K (table 1) [2].
Tablel. - Correction coefficient with considering angle of turn of the excavator
Angle of rotation of the excavator on unloading, degree 45 60 75 90 120 150 180
Correction coefficient, K 0.79 0.86 0.93 1.00 1.14 1.26 1.40
The size of the angle of turn on unloading — depends on the schemes ofmovement oftransport, servicing an excavator in career.
Productivity of the excavator with considering noted coefficients on loose mass is determined (in cubic meters per hour) by the formula [4].
T
" :> (2)
Kf
Qrech = Qt —
k, (T + Ta)
where K — coefficient of filling of bucket, equal to the ratio the volume ofloosened rock mass in a bucket to passport capacity of a bucket; Maximum K = 1.2; K{ — coefficient loosening of rock mass, characterized by the ratio of the volume of a ground in the loosened condition to the volume of the same ground in the dense body (entirely); T — duration of continuous operation of the excavator from one place of standing within an hour; for the approximated calculations can be accepted T = 45-50 min.; T — duration of advancing of the excavator as removing the face within an hour, equal to T = 10-15 min.
The total consumption of electricity for the full cycle of operation of the excavator is defined as the sum of the five components in accordance with the following structure (thus is accepted, that within a cycle of excavation of drives of the working equipment of the excavator are loaded on full capacity).
IWECT + Wfng + WM (B 1 + Wurn (B 2 + Wmove, (3)
where w — the electric power consumption on creation
pressure l l
of pressure; wkftirg — the electric power consumption on lifting;
W^tum(B l) — the electric power consumption on turn of a platform with the filled bucket; Wfum (B ^ — the electric power consumption on the reverse turn of the platform with the empty bucket; W — the electric power consumption on moving of the excavator.
move L L c
The specific consumption of electrical energy of the ECT on production 1m 3 ores will be:
Äl (4)
N
iy ECT
Qt
where Q— Theoretic productivity of the excavator per unit time.
Knowing the total power consumption of each component of a unified cycle of pressure mechanisms, lifting, turning the laden bucket, turn of the emptied bucket, moving, can be determined necessary electrical energy (energy consumption) for one cycle of the excavator work. In figure 1 the scheme of electric equipment and working mechanisms taking into account the efficiency of each component is presented. The excavator is powered three-phase AC voltage from a career network of electric supply.
Knowing the needs of the mechanical power for each component, that is the necessary power for realization of the pressure, lifting, turning to the laden and emptied bucket, the mechanism of moving of the excavator, it is possible to calculate the power requirement for each component. Knowing the efficiency of each component, will determine the total efficiency for operation of a pressure, lifting, turning and moving.
Fig.1. Structural scheme of electric equipment and working mechanisms of the excavator ECT-5A for systems AE-G-M (asynchronous engine- generator-motor DC), taking into account of efficiency of each component of executive mechanisms.
Total efficiency for each operation of component of the cycle will be:
1. Efficiency of pressure
n pressure n trans. n AE n gen. pres. nD.pres. n mech .pres.i (5)
2. Efficiency of lift:
Vlift ~V'trans. 'VaE ' ngen.lift ' VD.lift 'Vmech.lift ' (6)
3. Efficiency of turn B-1:
nturn (B-1) n trans. ^ AE ^ gen .turn ^ D .turn ^ mech.turn ' (7)
4. Efficiency of turn B-2:
n turn (B-2) n trans. n AE ^ gen .turn ^ D .turn ^ mech.turn ' (8)
5. Efficiency of move:
Imove I trans. IAE I gen.move ID.move Imech.move (9)
The total power consumption on an entrance of the transformer for each component of the cycle will be equal:
S WECT ^pressure ' + Plift ' ^2 + Pturn (B-1) ' tr3 + Pturn (B-2) ' ' ( 1 1 )
where t1, t^, t3, t4 — accordingly time necessary for performance of operation of pressure, lifting, turning of platform with the filled bucket, turn of reverse motion of a platform with an empty bucket.
The specific norm of the consumption of electrical energy without taking into account component of the mechanism of a move will be:
yw
\T - ¿^yyE
w + wf +w
pressure lift tu
+ W
3-1) ^ turn (B-2)
p mech.pres. P •j-) mech.lift P T) mech.ture
n pressure , Plift , n 1 turn (B-1) Vturn (B-1)
P = turn (B-2) p _ mech.ture p Vturn (B-2) P . mech.move n move
(10)
Knowing the power of each component, we shall determine the amount of the consumed electric power:
Q Q (12)
ECT ECT
where QeCT — the volume of excavation for the estimated time m3.
Experimental part
The calculation-experimental method is based on results of measurements of the consumption of electrical energy of each component of operation of a uniform cycle of work of the excavator or the total consumption of electrical energy for the certain period of time (hours or days).
On figures 2-7 are shown in the form of oscillograms daily measurements of indicators of the consumption of electrical energy, the schedule of voltage, current and power factor taking into account the coefficient of current transformer k = 300/5 = 60 and voltage k = 110000/100 = 1100.
pressure
Fig. 2. The daily schedule of active powers on phases of the ECT-5A taking into account coefficient of the transformer of current and voltage
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Fig. 3. The daily schedule of full powers on phases of the ECT-5A taking into account coefficient of the transformer of current and voltage
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Fig. 4. The daily schedule of voltage on phases of the ECT-5A
Fig. 5. The daily schedule of currents on phases of the ECT-5A taking into account coefficient of the transformer of current and voltage
Fig. 6. The daily schedule of frequency of network of the ECT-5A
Fig. 7. The daily schedule of power
Results and Discussion
Thus, as shown experimental data of each cycle, the consumption of electrical energy has a large spread by results of measurements, on what influences range of the factors marked earlier.
The basic unaccounted parameters at definition of the consumption of electrical energy are load factor on power and coefficient ofutilization ofthe equipment in time, as well as organizational and other unaccounted factors.
As shown experimental data, power consumption of excavators cannot be defined for one cycle of the work because of non-uniformity of indicators of schedules — it is necessary to consider a period of time, at least, daily.
Conclusions
1. The composition of electrical equipment is determined, taking into account the efficiency of the constituting participating in the execution of each operation a complete cycle of operation (pressure, lifting, turn taking into account the reverse and move) for career excavators.
2. A method of calculating the power consumption of career excavator calculation and analytical methods based
factors on phases of the ECT-5A
on given values of the efficiency of each component ofthe electrical equipment and machinery in general is developed with the known value of their efficiency and power consumption of the actuating mechanism (pressure, lifting, turn taking into account the reverse and move). The method is suitable as for systems of the electric drive thyristor converter — DC motor and for system frequency converter — asynchronous motor with the squirrel-cage rotor in view of deletion of the electrical equipment, not participating at performance of works of a full cycle.
3. Calculation-experimental method is based on measurement results of electrical energy consumption of each component of the operations of a single cycle of operation excavator or the total consumption of electrical energy for a certain period of time (hours). Thus, as shown experimental data, since the consumption of electric energy has a great dispersion by results of measurements in order to reduce the influence of a number of undesirable factors, for the period of time it is expedient to accept day.
References:
1. Pavlenko S. Improving the efficiency of functioning of the electrotechnical system of career excavators//Scientific analytical and industrial journal "Mining equipment and Electromechanics." - M., 2011. - № 4. - P. 47-52.
2. Encyclopedias of the mechanics of the open works. Excavation transport machines of cyclic action/Schadov M., Poderni R. - M.: Nedra, 1989. - 374 p.
3. Portnoy T., Parfyonov B., Kogan A. Modern condition and directions of development of electrotechnical complexes of single-bucket excavators. - M.: JSC "Electric drive", 2002. - 114 p.
4. Hmyznikov K. Mechanical the equipment of career. Single-bucket excavators: Textbook. - St. Petersburg, 2007. - 41 p.
