RU2563337C2 - Method and device for electric furnace heater control - Google Patents

Abstract

FIELD: heating.

SUBSTANCE: invention refers to engineering physics, particularly to control methods and devices for physical parameters, such as viscosity, electric conductivity, density, surface tension, in melted metal samples. It can be used at metallurgical facilities, in research centres, laboratory works at institutes. The method is based on parameter measurement in one coil of power transformer and involves comparison of parameters measured with a preset threshold value, and of an electric parameter exceeds the threshold a decision is made as to halt and replace the heater. Device includes heater, power transformer, thermal controller, parameter monitoring unit connected to one coil of the power transformer, temperature sensor, thermocouple, computer connected to the thermal controller, temperature sensor and control units for physical parameters, and additionally features comparator consisting of two units with programmable thresholds, multiplexer, differentiating unit, AND logical device, where signal inputs of multiplexer are connected to parameter control unit, control input of parameter control unit is connected to the computer, and output bus is connected to one of AND inputs while the other AND input is connected to temperature sensor connected in parallel to one of inputs of the differentiating unit and to the computer while the other input of differentiating unit is connected to AND output, comparator unit outputs are connected to the computer, input of one comparator unit is connected to differentiating unit output, and input of the other comparator unit is connected to output of AND logical device.

EFFECT: elimination of unpredictable interruption of experiments, faster operation, more simple and cost-effective elements.

4 cl, 6 dwg

Description

The present invention relates to technical physics, namely, to methods and devices for non-contact laboratory determination, control and measurement of physical parameters — viscosity, electrical conductivity, density, surface tension in samples of metal melts, for example, based on Fe, in vacuum furnaces. The invention can be used in laboratory research, at metallurgical enterprises, when performing work in universities.

составляет, например, для нихрома почти 1400°C, при рабочей температуре t° до 1000°C, эти нагреватели надежны, в частности срок их службы составляет 2÷5 тысяч часов. Кроме того, качество нагревателя можно контролировать непосредственно, визуально оценивая однородность и интенсивность его свечения, для чего, например, использовать тепловизор, а обрыв нагревателя можно определить посредством контроля целостности электрических цепей.It is well known to use the thermal effect of an electric current based on the Joule-Lenz law to heat a heating element with an electrical resistance R, which is the main unit of devices that are used to heat various substances or materials, for example, used in industrial technological processes, in domestic conditions, in food industry, when heating rooms, etc. A heating element with an electric current P released on it up to 1 ÷ 3 kVA is a predominantly high-resistance metal, for example, nichrome, conductor, which is placed near the heated substance. In this case, both contact and non-contact, by means of radiation, heating are used, and in some cases the temperature t ° is controlled by temperature regulators with temperature sensors. Due to the fact that heaters are often used up to temperatures t ° below 700 ° C, and their melting temperature $$t_{Pl}^{\circ }$$

for example, for nichrome almost 1400 ° C, at an operating temperature of t ° up to 1000 ° C, these heaters are reliable, in particular, their service life is 2 ÷ 5 thousand hours. In addition, the quality of the heater can be directly controlled by visually assessing the uniformity and intensity of its glow, for which, for example, using a thermal imager, and the breakage of the heater can be determined by monitoring the integrity of the electrical circuits.

) металлов либо сплавов на основе Fe, Ni, Co, Ti, или шлаков, которые размещены в тигле или на подложке. Эти условия характерны для установок в металлургии, выполненных с применением водоохлаждаемых электропечей, питающихся от силовых электросетей мощностью 10÷30 кВА. - см. П.П. Арсентьев и др. «Физико-химические методы исследования металлургических процессов», М., Металлургия, 1988, с.136, 137, рис.V.3, с.119, рис.IV-5 - аналог.Known methods that implement the determination of the physical parameters of samples of metal melts, a volume of several cm ³ and a mass of tens of grams, by means of devices containing crucible metallurgical laboratory vacuum water-cooled electric resistance furnaces. In them, the quality of the heater, for example, metal molybdenum (Mo), is not accessible to direct visual control, since the heater is located inside the furnace body. It is noted that the electric furnace heater is the most important element of the measuring installation - see A.V. Rowan and others. "Bezlektrodnga method of measuring the electrical resistance of metals in solid and liquid states and installation for its implementation", Zh. “Melts”, 2009, 1, p. 36 ÷ 42. The electrical parameters of the heater are indirectly controlled on one of the windings of the power transformer to which the heater is connected, mainly by determining the values of current I and voltage V using an ammeter and voltmeter. The operating temperature in an electric furnace can be close to the melting temperature of the heater material and reach the values necessary for the melting of the studied materials, in particular high-temperature ( $$t_{Pl}^{\circ }=1000÷{2000}^{\circ }C$$

) metals or alloys based on Fe, Ni, Co, Ti, or slag, which are placed in a crucible or on a substrate. These conditions are typical for installations in metallurgy made using water-cooled electric furnaces powered by power networks with a capacity of 10–30 kVA. - see P.P. Arsentiev et al. “Physicochemical Methods of Investigation of Metallurgical Processes”, Moscow, Metallurgy, 1988, p.136, 137, fig. V.3, p.119, fig. IV-5 - analogue.

. В третьих, сложно оценить динамику изменения R и ρ нагревателя когда он подключен к силовому трансформатору, в частности, с учетом комплексной составляющей общего импеданса Z системы «нагреватель-трансформатор», в том числе индуктивного сопротивления, а также неравномерности разогрева нагревателя, дополнительного теплоотвода от него за счет водоохлаждения и массивных токоподводов. Таким образом, прямое определение состояния нагревателя посредством измерения сопротивления R не имеет преимущества перед визуальной оценкой этого состояния, также требует остановки эксперимента, отключения и разборки измерительной установки.Assessing the quality of the heater by measuring the electrical resistance R, amounting to units of mOhm, for example, an ohmmeter, and / or electrical resistivity ρ, can be carried out, First, only in the intervals between experiments, when the heater is disconnected from the power transformer, which is technologically difficult. Secondly, it is almost impossible to take into account the temperature coefficient of resistance (TCS) of the heater material and the corresponding changes $$R\left(t_i^{\circ }\right)$$

. Thirdly, it is difficult to assess the dynamics of changes in R and ρ of the heater when it is connected to a power transformer, in particular, taking into account the complex component of the total impedance Z of the heater-transformer system, including inductive resistance, as well as the uneven heating of the heater and additional heat removal from him due to water cooling and massive current leads. Thus, the direct determination of the state of the heater by measuring the resistance R does not have an advantage over the visual assessment of this state, it also requires stopping the experiment, shutting down and disassembling the measurement setup.

, критическую $$t_{кр}^{\circ }$$

и температуру аномального изменения свойств расплава $$t_{ан}^{\circ }$$

, а также гистерезисные характеристики цикла «нагрев - охлаждение». Эксперименты осуществляет квалифицированный персонал, при большом энергопотреблении и многочасовых подготовительных работах. Используют преимущественно компьютерный контроль электрических параметров и температуры в изотермической зоне, в том числе для управления терморегулятором и фазоимпульсным тиристорным блоком управления нагревом, т.е. током нагревателя, в том числе и для аварийного отключения силового напряжения при снижении напора охлаждающей электропечь воды или иных нештатных ситуациях - см. вышеуказанное Л.Д. Сон и др… Однако, неизбежно возникает, иногда в течение 1÷2 недель, а иногда и в течение многомесячных (до 6÷9 месяцев) экспериментов, преимущественно в зависимости от температуры плавления $$t_{пл}^{\circ }$$

исследуемых сплавов, ухудшение достоверности и надежности полученных в ходе экспериментов результатов, обусловленных, прежде всего, возрастанием как электросопротивления R и удельного электросопротивления ρ, так и испарением Mo - нагревателя внутри электропечи, его последующего прогорания и обрыва. Вышеизложенное вызывает сначала уменьшение точности полученных результатов, а в конечном итоге непрогнозируемое аварийное прекращение эксперимента. Снижение качества нагревателя электропечи, в изотермической зоне которого помещен тигель с изучаемым расплавом, выражается в виде образования в нагревателе локальных дефектов, в том числе трещин или отверстий, с частичным испарением материала нагревателя, с локальным возрастанием плотности тока, а в дальнейшем происходит перегорание нагревателя. Пары Мо оседают в виде пыли внутри водоохлаждаемой электропечи, в том числе на образцах исследуемого расплава, и некоторых случаях могут изменить его характеристики, например при изучении поверхностного натяжения и плотности расплава. Вышеизложенное обусловливает замедление, усложнение и удорожание экспериментов.It is known that the determination of the physical parameters of metal melts is realized, inter alia, by studying the temperature dependences of the viscosity, density, surface tension, or electrical conductivity of a sample using a rotating magnetic field in a sample placed in a crucible or on a substrate, which are placed inside a vacuum electric furnace heater in areas of the isothermal zone, with computer control of the course of experiments - see A.L. Beltyukov, V.I. Ladyanov “Automated installation for determining the kinematic viscosity of metal melts”, Zh. "Instruments and experimental techniques", 2008, No. 2, pp. 155 ÷ 161 - analogue; L.D. Son et al. “Installation for measuring viscosity, surface tension and density of high-temperature melts”, proceedings of the X Russian conference “Structure and properties of metal and slag melts”, vol. 2, ed. SUSU, 2001, from 47 ÷ 50 - analogue. After analyzing the temperature dependences of the physical characteristics of the alloys, the researchers make recommendations for obtaining alloys with the given characteristics, in particular, they adjust the technological conditions. The analysis allows, inter alia, to highlight specific temperature points, in particular, the temperature of the onset of hysteresis $$t_g^{\circ }$$

critical $$t_{\mathrm{to}R}^{\circ }$$

and temperature of abnormal changes in the properties of the melt $$t_{\mathrm{but}n}^{\circ }$$

, as well as the hysteresis characteristics of the heating – cooling cycle. Experiments are carried out by qualified personnel, with high energy consumption and many hours of preparatory work. They mainly use computer control of electrical parameters and temperature in the isothermal zone, including for controlling a temperature controller and a phase-pulse thyristor heating control unit, i.e. the heater’s current, including for emergency shutdown of the power voltage when the pressure of cooling water cooling the furnace or other emergency situations decreases - see the above L.D. Sleep and others ... However, inevitably arises, sometimes during 1 ÷ 2 weeks, and sometimes during many months (up to 6 ÷ 9 months) of experiments, mainly depending on the melting temperature $$t_{Pl}^{\circ }$$

of the studied alloys, deterioration of the reliability and reliability of the results obtained during experiments, primarily due to an increase in both electrical resistance R and electrical resistivity ρ, and the evaporation of the Mo - heater inside the electric furnace, its subsequent burning and breaking. The foregoing causes first a decrease in the accuracy of the results obtained, and ultimately an unpredictable emergency termination of the experiment. The decrease in the quality of the electric furnace heater, in the isothermal zone of which the crucible with the studied melt is placed, is expressed as the formation of local defects in the heater, including cracks or holes, with partial evaporation of the heater material, with a local increase in current density, and then the heater burns out. Mo vapors are deposited in the form of dust inside a water-cooled electric furnace, including samples of the studied melt, and in some cases they can change its characteristics, for example, when studying the surface tension and density of the melt. The foregoing leads to a slowdown, complication and appreciation of experiments.

The prototype of the proposed method is a method for monitoring the operation of an electric furnace heater connected to a power transformer, based on measuring one or more electrical parameters on one of the windings of the power transformer, in particular, the magnitude of the current and / or voltage and / or power consumption - see above A .AT. Mountain ash and others.

A prototype of the proposed device is a device for monitoring the operation of an electric furnace heater, comprising an electric furnace heater, a power transformer, a temperature controller connected to one of the windings of the power transformer, a control unit for electrical parameters, in particular, current and / or voltage and / or power consumption connected to one of the windings of a power transformer, a temperature sensor, for example, a thermocouple, a computer connected to a temperature controller, a temperature sensor and electrical control units parameters, see above A.V. Mountain ash and others.

The disadvantages of the method and device specified both in analogues and in the prototype are, Firstly, the possibility of unpredictable interruption of the experiment due to the inoperative state of the heater, and ultimately, the lack of the ability to ensure the reliability and accuracy of the determination of the measured parameters of metal melts, in particular, high temperature; Secondly, the slowdown, complication and cost of the experiments due to the above-mentioned interruption of the experiment; thirdly, the non-zero probability of uncontrolled interaction of the material of the damaged heater and the melt sample during the experiment; fourthly, the inability to make an informed decision on the termination of the heater, in particular for its replacement.

The objective of the invention is to eliminate the unpredictable interruption of experiments due to the inoperative state of the heater, acceleration, simplification and cheapening of experiments, in addition to eliminating the possibility of uncontrolled interaction of the heater material with the melt sample during the experiment, making it possible to make an informed decision on the termination of the heater, in particular to replace it, and ultimately ensure the reliability and accuracy of the results RH.

To solve this problem, a method and device for controlling the operation of an electric furnace heater are proposed.

1. A method of monitoring the operation of an electric furnace heater connected to a power transformer, based on the measurement of one or more electrical parameters on one of the windings of the power transformer, characterized in that

the measured electric parameter is compared with a predetermined threshold value; when the electric parameter reaches the threshold value, a decision is made to stop the heater.

2. A device for monitoring the operation of an electric furnace heater, comprising an electric furnace heater, a power transformer, a temperature controller connected to one of the power transformer windings, electrical parameter control units connected to one of the power transformer windings, a temperature sensor, a computer connected to a temperature controller, a temperature sensor and control units for electrical parameters, characterized in that two comparison units with electrical values for each of them are adjusted according to Ogove values U U _{por.1 por.2,} a multiplexer, a differentiating unit, the logic unit 'AND', multiplexer signal inputs are connected to the control units of electric parameters, its control input connected to the computer, and the output bus is connected to one input of the logic device " And ”, the other input of which is connected to a temperature sensor connected in parallel to one of the inputs of the differentiating unit and the computer, the other input of the differentiating unit is connected to the output of the logical device“ I ”, the outputs of the blocks are equal Ia connected to a computer, the input of one of comparators connected to the output of the differentiating block of another comparator input connected to the output of the logical device "U".

3. A device for monitoring the operation of an electric furnace heater according to claim 2, characterized in that the electric parameter control units are made in the form of meters of current and / or voltage and / or power consumption.

4. A device for monitoring the operation of the electric furnace heater according to claim 2, characterized in that the temperature sensor is made in the form of a thermocouple.

The technical result of the invention is the elimination of unpredictable interruption of experiments, the acceleration, simplification and cheapening of experiments, the elimination of the possibility of interaction of the heater material with the melt during the experiment, the possibility of making an informed decision about the termination of the heater, in particular for its replacement, and ultimately the reliability and accuracy of the results.

The invention is illustrated by drawings:

FIG. 1. The block diagram of the measuring complex;

FIG. 2. The appearance of the new heater;

figure 3. Appearance of a burned-out heater;

figure 4. Estimated Thermal Dependence of Electrical Parameters I, V, P;

figure 5. Experimental thermal dependence of current I and voltage V;

Fig.6. Experimental thermal dependence of power P and impedance Z.

The proposed method is implemented by means of a device for monitoring the operation of the electric furnace heater, the main nodes of which are shown in the block diagram - see figure 1. The device contains a heater 1, inside which the studied melt is placed, for example, in a crucible or on a substrate (not shown in the diagram), a power transformer 2, a temperature regulator 3, a water-cooled electric furnace 4, a computer 5, an electrical parameter control unit 6, a temperature sensor 7, and a comparison device 8, containing comparison blocks 9 and 10, with adjustable for each of them values of electrical threshold values U _pore 11 11 and U _{pore 2} 12, multiplexer 13, differentiating block 14, logic device “I” 15. Cylindrical thin-walled (0, 4 mm) Mo - heater 1 with a diameter of 30 mm is connected to the secondary low-voltage (6 ÷ 10 V) winding of a power transformer 2 of the original manufacture with a power of 20 kVA with a transformation coefficient n = 0.027. Temperature regulator 3 - phase-phase load control unit with current I up to 160 A, type МТТМ1Ф160М1 of Meradat company - see the operating instructions for МТТМ1Ф160М1. It controls the opening angle of the thyristors φ = Ψ (t °) and regulates, through the power transformer 2, the current in the heater 1. The temperature controller 3 displays the temperature t ° measured by thermocouple 7 of type VR-5/20 in the heating zone directly near the heater 1 Computer 5, no lower than Pentium 4, controls the experiment. The control unit for electrical parameters 6 is made in the form of multimeters measuring alternating current I and / or voltage V, such as ЩП-120П, connected to computer 5 via the RS-485 interface. They can measure current with current transformers, for example 200/5 A. Comparison units 9, 10, and differentiating unit 14 are made on one of the operational amplifiers each, which are part of the LM324 quadruple chip. Multiplexer 13 - chip K561KP2, logical device "I" 15 - chip K561LA7. Adjustable values of the electrical thresholds U _por 11 11 and U _{por 2} 12 are set by one of the inputs of each comparison unit 9 and 10 (operational amplifiers), for example, manually based on data from previous experiments, or using an automated control system with the generation of U _{por. 1} 11 and U _{p. 2} 12 by computer 5 on the basis of this data accumulated in the memory of computer 5 for a certain period, for example, for 0.5 years. The comparison device 8 can be implemented as a virtual device as part of a computer 5 or based on a microcontroller, for example, STM32 company "STM" connected to a computer 5.

. Перед перегоранием нагревателя 1 отмечено, что в области конечной температуры эксперимента $$t_i^{\circ }={1400}^{\circ }C$$

электрические параметры блока контроля электрических параметров 6 следующие: I=35 A, V=140 B, P=4,9 кВА при угле отсечки тиристоров φ_т=86 град. Ток нагревателя 1, с учетом n силового трансформатора 2, составляет 1,3 кА. Масса нового Мо - нагревателя 1 была равна m₁=107 граммов. После того, как нагреватель 1 перегорел, был извлечен из электропечи 4 и взвешен, его масса m₂=104 грамма, т.е. дефицит массы составляет 3 грамма. Эта масса постепенно испарялась и оседала в виде пыли внутри водоохлаждаемой электропечи 4, в том числе и на образцах. Внешний вид нового нагревателя 1 приведен на фиг.2, а сгоревшего - на фиг.3. Как отмечено выше, такая ситуация может быть опасна в том числе из-за возможности непредсказуемого попадании части испарившегося Мо в изучаемый расплав, в частности в установках изучения поверхностного натяжения и плотности методом «большой капли» - см. вышеуказанное Л.Д. Сон и др…Determination of the mass deficit of Mo heater 1, which appeared during its service life before burnout, was carried out during experiments to study the viscosity of Fe alloys, in particular GM414, used for the manufacture of an amorphous transformer tape, in which $$t_{Pl}^{\circ }={1100}^{\circ }\mathrm{FROM}$$

. Before burnout of heater 1, it was noted that in the region of the final temperature of the experiment $$t_i^{\circ }={1400}^{\circ }C$$

The electrical parameters of the electrical parameters control unit 6 are as follows: I = 35 A, V = 140 V, P = 4.9 kVA with a thyristor cut-off angle of φ _t = 86 deg. The current of the heater 1, taking into account n power transformer 2, is 1.3 kA. The mass of the new Mo - heater 1 was equal to m ₁ = 107 grams. After the heater 1 burned out, was removed from the electric furnace 4 and weighed, its mass m ₂ = 104 grams, i.e. the mass deficit is 3 grams. This mass gradually evaporated and settled in the form of dust inside a water-cooled electric furnace 4, including samples. The appearance of the new heater 1 is shown in figure 2, and the burnt - in figure 3. As noted above, this situation can be dangerous, including due to the possibility of unpredictable ingress of part of the evaporated Mo into the studied melt, in particular, in installations for studying surface tension and density by the “big drop” method - see the above L.D. Sleep and more ...

нагрева образцов. Иллюстративные предполагаемые температурные зависимости этих параметров, изменяющиеся по мере старения нагревателя 1 от начальных значений 16 до критических значений 17 перед сгоранием нагревателя 1, приведены на фиг.4. Ток I и мощность P должны уменьшаться, а напряжение V незначительно расти. Пороговой величиной 18, оптимально отражающей предшествующие перегоранию нагревателя изменения и полученной прямыми измерениями, является ток I_пор.. Дополнительно может быть использована пороговая величина 18 напряжения V_пор. и/или мощности электротока P_пор, либо все пороговые величины одновременно.To select the optimal electrical parameter and threshold values according to the criterion of variability, in particular the total current I _pore consumed by the heater 1 and power transformer 2, at the corresponding voltage V _pore and power P _pore , six-month experiments were conducted with the registration of these electrical parameters over the entire temperature range $$t_i^{\circ }$$

heating samples. Illustrative assumed temperature dependences of these parameters, which change as the heater 1 ages, from the initial values 16 to critical values 17 before the combustion of the heater 1, are shown in FIG. 4. The current I and power P should decrease, and the voltage V should increase slightly. The threshold value 18, which optimally reflects the changes preceding the burnout of the heater and obtained by direct measurements, is the current I _pore. . Additionally, a threshold value of voltage 18 V _then can be used _. and / or electric current power P _then , or all threshold values simultaneously.

образцов, построенная из ряда значений пороговой величины 18. Линия представляет собой отношение приращений измеряемого электрического параметра к приращениям температуры $$t_i^{\circ }$$

нагрева образцов или ее производную $$d{I}_{пор.}/d{t}_i^{\circ }$$

, причем монотонному по времени уменьшению значения $$d{I}_{пор.}/d{t}_i^{\circ }$$

соответствуют возрастающий износ и большая вероятность перегорания нагревателя 1. Для этого используют имеющиеся в устройстве сравнения 8 дифференцирующий блок 14 и второй блок сравнения 10 с регулируемым значением электрических пороговых величин U_пор.2 12. Устройство для контроля работы нагревателя 1 электропечи 4 может быть использовано без этих блоков, однако в спорных случаях для уточнения оценки и выбора пороговой величины 18 целесообразно определение $$d{I}_{пор.}/d{t}_i^{\circ }$$

путем использования этих блоков.In addition, a line (not shown in the diagram) can serve as an additional characteristic for estimating and choosing threshold value 18, a sloping straight line in the first approximation, in the temperature range up to temperatures exceeding (100 ÷ 300) ° C the melting temperature $$t_{Pl}^{\circ }$$

samples, built from a number of threshold values 18. The line is the ratio of the increments of the measured electrical parameter to the increments of temperature $$t_i^{\circ }$$

heating samples or its derivative $$d{I}_{P\mathrm{about}R.}/d{t}_i^{\circ }$$

, and monotonically decreasing in time $$d{I}_{P\mathrm{about}R.}/d{t}_i^{\circ }$$

correspond to increasing wear and a greater likelihood of burnout of heater 1. To do this, use the differentiator block 14 and the second comparison block 10 with the adjustable value of the electrical threshold values U _{pore 2} available in the comparison device 8 12. The device for monitoring the operation of the heater 1 of the electric furnace 4 can be used without of these blocks, however, in disputed cases, it is advisable to determine $$d{I}_{P\mathrm{about}R.}/d{t}_i^{\circ }$$

by using these blocks.

When the electrical parameters reach a threshold value of 18, the experimenter decides to replace the heater 1. The value of the threshold value 18 in the form of I _pores. and / or V, P can be used for automatic control and alarm, for example, on the display of computer 5, about the need to replace the heater 1, as well as blocking and / or emergency shutdown in this case, the power transformer 2. The value of the threshold value 18 used to generate a control signal (not shown in the diagram), for example, a pulse that is entered into the temperature controller 3 manually or by computer 5.

для Mo - нагревателя 1, полученные при отмеченной выше полугодовой работе по определению кинематической вязкости образцов сплавов на основе Fe вплоть до температур $$t_i^{\circ }$$

, превышающих на (100÷300)°C температуру плавления $$t_{пл}^{\circ }$$

исследуемых образцов, приведены на фиг.5, 6. Основной массив 19 данных экспериментов соответствует требуемому состоянию нагревателя 1, критический набор данных 20 отражает предпоследний эксперимент и критическое состояние нагревателя 1, данные 21 отражают аварийно прерванный эксперимент, во время которого нагреватель 1 перегорел до достижения, при t°=1400°C. Пороговая величина 18 тока I_пор, которая в качестве примера приведена при температуре $$t_{пл}^{\circ }$$

, одной из наиболее значимых в экспериментах, оптимальная по сравнению с пороговой величиной 18 для V_пор, P_пор (на фиг.4, 5, 6 не показаны). Значение I_пор=38 A, находящееся посредине между значениями в основном массиве данных 19: I_o=40 A и в критическом наборе данных 20: I_к=36 A при $$t_{пл}^{\circ }={1540}^{\circ }C$$

отличается от них по абсолютной величине на +/- 5%. Можно считать, что при уменьшении I_i на (5÷10) % по отношению к I_o, определенному в первых экспериментах с новым нагревателем 1, его замена обоснована.Experimental dependences of electrical parameters $$\left[I,V,P=V\times I,R\left(Z\right)=V/I\right]=\Psi \left(t_i^{\circ }\right)$$

for Mo - heater 1, obtained during the semi-annual work noted above to determine the kinematic viscosity of Fe-based alloy samples up to temperatures $$t_i^{\circ }$$

exceeding (100 ÷ 300) ° C melting point $$t_{Pl}^{\circ }$$

the test samples are shown in FIGS. 5, 6. The main array 19 of these experiments corresponds to the required state of the heater 1, the critical data set 20 reflects the penultimate experiment and the critical state of the heater 1, data 21 reflects an aborted experiment during which the heater 1 burned out before reaching at t ° = 1400 ° C. The threshold value of 18 current I _then , which as an example is given at temperature $$t_{Pl}^{\circ }$$

, one of the most significant in the experiments, is optimal compared to the threshold value of 18 for V _pores , P _pores (not shown in FIGS. 4, 5, 6). The value of I _pore = 38 A, located in the middle between the values in the main data array 19: I _o = 40 A and in the critical data set 20: I _k = 36 A at $$t_{Pl}^{\circ }={1540}^{\circ }C$$

differs from them in absolute value by +/- 5%. We can assume that when I _i decreases by (5 ÷ 10)% with respect to I _o determined in the first experiments with the new heater 1, its replacement is justified.

: Z_пор=4,2 Ом × n²=3,06 мОм, а величина R₁=6,12 мОм. Находящееся посередине между основным 19 и критическим 20 массивами данных вычисленное значение R₁ нагревателя 1 отличается от них на 6%, что близко к 5% - различиям прямо измеренного I_пор. Тенденция аварийного массива данных 21 демонстрирует даже для t°=1400°С уменьшение измеренного значения I, практически неизменное значение V и уменьшение вычисленного значения P, а также превышение вычисленных значений Z и соответственно R₁ над аналогичными параметрами критического массива данных 20. Эти данные свидетельствуют о неконтролируемом локальном нарастании R₁ и в конечном итоге локальных увеличений плотности тока. Если выбирать пороговое значение I_пор из значений критического массива данных 20, различие достигнет 10%. Использование V_пор при аналогичных условиях обеспечивает (2÷3) % различие, P_пор обеспечивает (6÷12) %, в соответствии с формулой P=I×V.Calculated on the primary winding of the ratio V / I value of the impedance Z, consisting of parallel-connected R ₁ of the heater 1, as well as coordinated by power, i.e., in a first approximation, R ₁ = Z _Tr , and converted to the secondary winding of the impedance Z _{Tr of} power transformer 2 at a frequency of 50 Hz, are: Z = R _1/2 and, accordingly, R ₁ = 2 × Z. R _{1 of the} heater 1, taking into account n power transformer 2, is: R ₁ = 2 × Z × n ² . When n = 0.027, n ² = 7.3 × 10 ^-4 , therefore, for the main data array 19, the value of R ₁ is in the range 2 (3.5 ÷ 4.1) × n ² = 2 (2.55 ÷ 2, 99) = (5.1 ÷ 5.98) mOhm. For the critical data set 20, similarly, the value of R ₁ is in the range 2 (3.13 ÷ 3.57) = (6.26 ÷ 7.14) mOhm. Estimated threshold value for $$t_{Pl}^{\circ }={1540}^{\circ }C$$

: Z _pore = 4.2 Ohm × n ² = 3.06 mOhm, and the value of R ₁ = 6.12 mOhm. Located in the middle between the main 19 and critical 20 data sets, the calculated value of R _{1 of the} heater 1 differs from them by 6%, which is close to 5% - differences directly measured I _then. The trend of the emergency data array 21 even shows for t ° = 1400 ° C a decrease in the measured value of I, a practically unchanged value of V and a decrease in the calculated value of P, as well as an excess of the calculated values of Z and, accordingly, R ₁ over the same parameters of the critical data array 20. These data indicate about an uncontrolled local increase in R ₁ and ultimately local increases in current density. If you select a threshold value of I _then from the values of the critical data array 20, the difference will reach 10%. The use of V _then under similar conditions provides (2 ÷ 3)% difference, P _then provides (6 ÷ 12)%, in accordance with the formula P = I × V.

Thus, the use, based on the data recorded during the experiments, of the threshold values of the values of the electrical parameters I and / or V, available for direct measurement on one of the windings of the power transformer, as well as the measured or calculated value of P, makes it possible to monitor the quality of work electric furnace heater, eliminating the unpredictable interruption of experiments and making an informed decision on the continuation or termination of experiments to replace the heater, acceleration, control growing and reducing the cost of experiments, eliminating the possibility of uncontrolled interaction of the heater material with the melt sample during the experiment, and ultimately ensuring the reliability and accuracy of the results.

Technical solutions containing the above combination of distinctive features, as well as a combination of restrictive and distinctive features, are not identified in the prior art, which, when the above technical result is achieved, allows us to consider the proposed technical solution as inventive.

Claims (4)

1. A method of monitoring the operation of an electric furnace heater connected to a power transformer, based on measuring one or more electrical parameters on one of the windings of the power transformer, characterized in that the measured electrical parameter is compared with a predetermined threshold value, when the electrical parameter reaches the threshold value, a decision is made about the termination of the heater. 2. A device for monitoring the operation of an electric furnace heater, comprising an electric furnace heater, a power transformer, a temperature controller connected to one of the power transformer windings, electrical parameter control units connected to one of the power transformer windings, a temperature sensor, a computer connected to a temperature controller, a temperature sensor and control units for electrical parameters, characterized in that two comparison units with electrical values for each of them are adjusted according to Ogove values U U _{por.1 por.2,} multiplexer differentiator, a logical AND unit, the signal inputs of the multiplexer are connected to the control units of electric parameters, its control input connected to the computer, and the output bus is connected to one input of AND logic device, other the input of which is connected to a temperature sensor connected in parallel to one of the inputs of the differentiating unit and the computer, the other input of the differentiating unit is connected to the output of the logical device AND, the outputs of the comparison blocks under are connected to the computer, the input of one of the comparison blocks is connected to the output of the differentiating block, the input of another comparison block is connected to the output of the logical device I. 3. A device for monitoring the operation of an electric furnace heater according to claim 2, characterized in that the electric parameter control units are made in the form of meters of current and / or voltage and / or power consumption. 4. A device for monitoring the operation of an electric furnace heater according to claim 2, characterized in that the temperature sensor is made in the form of a thermocouple.

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