WO2020071944A1

WO2020071944A1 - Method for stirring molten metal and electromagnetic stirrer for the implementation thereof (variants)

Info

Publication number: WO2020071944A1
Application number: PCT/RU2018/000661
Authority: WO
Inventors: Евгений Анатольевич ГОЛОВЕНКО; Антон Андреевич АВДУЛОВ; Евгений Сергеевич КИНЕВ; Vladimir Evgen'evich TIMOSHEV (ТИМОШЕВ, Владимир Евгеньевич)
Original assignee: Общество с ограниченной ответственностью "Диотон"
Priority date: 2018-10-05
Filing date: 2018-10-05
Publication date: 2020-04-09
Also published as: RU2708036C1

Abstract

The inventions relate to the field of metallurgy and electrical engineering. In the present method, current phases to connected coil groups are set so that the pole pitch of an induction coil in terms of the magnetomotive force of the coil groups is (0.7-2.2) Δπ, the total width of the phase belts in terms of magnetic fluxes is up to 400 electrical degrees, and the active length of the induction coil has a fractional number or odd number of pairs of magnetic poles of the induction coil, but not more than 2. In the claimed electromagnetic stirrer, the number of end coil groups is greater than the number of turns of the central coil group, which is inverted relative to the end coil groups by virtue of the winding direction or the connection scheme, and the coil groups are connected using a "star" or "delta" connection scheme and are connected to the centre points of three pairs of power switches of a power supply inverter. According to another variant, the end coil groups are oppositely connected in series, and along the length of the core the even coil groups are inverted relative to the odd coil groups by virtue of the winding direction or the connection scheme. This provides optimal winding data at a given size of the working gap between the induction coil and the surface of the metal melt being stirred, and provides for the possibility of using semiconductor power supplies with three pairs of semiconductor power switches of an inverter.

Description

METHOD OF MIXING THE MELT OF METAL AND ELECTROMAGNETIC MIXER FOR ITS IMPLEMENTATION

(OPTIONS)

FIELD OF TECHNOLOGY

The group of inventions relates to the field of metallurgy and electrical engineering, in particular to methods and devices for force acting by a longitudinal traveling magnetic field on metal melts and can be used to mix metal melts in order to increase the melting speed of a solid charge, equalize the chemical composition and temperature throughout the volume of the melt , as well as for electromagnetic mixing of the liquid phase of the ingot during its crystallization.

BACKGROUND OF THE INVENTION

The prior art methods and devices for mixing a molten metal. Known low-frequency linear induction machine for exposure to a running magnetic field on metal melts in steel furnaces (Voldek A.I. Induction magnetohydrodynamic machines with a liquid metal working fluid. L .: Energy, 1970. -p. 152-153). The specified machine contains a two-phase winding, which is placed on the smooth surface of the inductor with the frontal parts bent to the side surfaces of the core, and in order to equalize the inductive resistances of the phases, the number of turns in the 2nd phase is taken 25-30% less than in the 1st phase. The windings are made of copper tubes and are water-cooled. During operation of the core winding, when powered by an alternating voltage of low frequency, an alternating traveling magnetic field is created, which induces currents in the molten metal located in the reservoir. The electromagnetic forces resulting from the interaction of induced currents with a magnetic field act on the metal melt, mixing it.

A disadvantage of the known device for mixing a molten metal is the high mass and dimensions, the complexity of its manufacture. The necessity of using large water-cooled copper tubes of large cross section, capable of operating at high operating currents and low voltages, is associated with the complexity of manufacturing windings with bending of the frontal parts to the side surfaces of the core and the lack of the possibility of rational matching of the inductor with the power source in terms of voltage due to an increase in the hydraulic resistance of the cooling water turns with an increase in the number of turns from water-cooled conductors, the need to ensure the reliability of numerous soldered joints and the difficulty of mounting the coil on the smooth surface of the inductor. As a result, water-cooled multiphase winding inductors have high currents and low voltage, which requires the use of specialized high-power power supplies.

A device for mixing a molten metal, comprising a core and placed on it two-phase windings (t = 2) in the form of concentric coils of a flat shape (autoswitch. SU180248, prior. 20.11.1965, Н02К). In this case, the coils of each phase form one layer. The winding is placed in such a way that the number of pairs of its poles corresponds to 2 (2p = 2), the number of teeth of the core Z = 16, the number of grooves per pole and phase q = 4, and the width of the phase zone a = 90 ° el. In the process, the device is installed at a distance from the reservoir with the molten metal with the formation of a working gap D between the surface of the device and the surface of the mixed molten metal. Then, power is supplied to the core windings, as a result of which a magnetic field is created, which induces currents in the molten metal located in the tank. The electromagnetic forces resulting from the interaction of induced currents with a magnetic field act on the metal melt, mixing it.

However, the described device has low efficiency due to the high number of pairs of magnetic poles per length, low pole division of the inductor and, therefore, the inability to work with an increased working gap D, in which refractory concrete and thermal insulation with an aggregate thickness of at least 500 mm are stored to preserve the melt thermal energy , and in some cases, with increased requirements for the mechanical strength of refractory concrete, up to 700 mm thick.

Known is a flat inductor of a Sherbius collector machine used in devices for mixing a molten metal, containing a core with many teeth and flat coils placed in grooves between these teeth in one or two layers (Voldek A.I. Induction magnetohydrodynamic machines with a liquid metal working fluid. L. : Energy, 1970 .-- pp. 148-149). The inductor is installed at a distance from the molten metal in the tank with the formation of a working gap D between the surface of the device and the surface of the mixed molten metal. They supply power to the core windings, as a result of which a magnetic field is created, which induces currents in the molten metal located in the tank. Arising from the interaction of induced currents with a magnetic field electromagnetic forces act on the molten metal, mixing and / or transporting it.

A disadvantage of the known inductor is that in spite of the simplicity of manufacturing flat coils without bends of the frontal parts, their location on the teeth of the inductor helps to reduce the coiling coefficient, since the windings of different phases are located in one groove, which demagnetize each other. A decrease in the cob winding coefficient, in turn, leads to a decrease in the magnetic field in the working gap D between the surface of the inductor and the surface of the mixed metal melt and, therefore, the efficiency of the machine as a whole. So, for example, when performing the described inductor with a single-layer winding with three distinct pole projections into double pole division, with the number of phases m = 3, the number of pole pairs 2p = 2, the number of core grooves Z = 6, the phase zone a - 120 ° el ., the number of coils in the phase zone Q = T and the relative step of the winding b = 2/3, the coil winding coefficient to ₀ b is 0.866, which reduces the inductor efficiency by about 25% and is very important for mixing the metal, although it is considered an acceptable value for electrical design This class in general. And when performing an inductor with a two-layer winding, the winding coefficient k _ob has values up to 0.75, which leads to an even greater decrease in machine efficiency (reduction to 50%) and is a critical value.

Known low-frequency linear induction machine for exposure to a running magnetic field on metal melts, including an inductor with three windings for a length with a phase zone of 60 ° el. (m = 3, 2p = 1, Z = 3, a = 60 ° e., b = 1/3, cob = 0.342) when turned on according to the AYC scheme, that is, an inverted central coil group (Neverov V.Yu. Flat unilateral linear induction machines with increased working clearance. Author's abstract of the dissertation of the candidate of technical sciences. Krasnoyarsk: 2010. - p. 20). The design features of the induction machine allow it to be used on large working gaps D due to a significant decrease in the rate of attenuation of the traveling magnetic field in the working gap D with a small number of magnetic poles per length and, consequently, a large pole division of the inductor.

However, the known inductor has low efficiency due to the reduced winding coefficient k ₀ , which necessitates compensating for a significant increase in weight and size indicators and the installed power of the electromagnetic stirrer as a whole. A device for mixing a molten metal containing a 111-shaped cross-sectional core and windings located in its grooves with the number of phases m = 2, the number of pole pairs 2p = 2, the number of core grooves Z = 4, the phase zone width a = 90 ° el ., the number of coils in the phase zone Q = l (ed. certificate SU1809507, prior 04/04/1989, Н02К41 / 025). The coils of the windings are divided along the height of the groove into several sections, placed in different parallel planes with alternating sections in the groove in phases and each of the windings immediately covers two teeth and one groove of the core. The design of the winding coils ensures the formation of longitudinal channels with respect to the grooves of the core for forced air cooling, which, together with a significant number of turns of the windings during operation, provides rational coordination of the induction load in the form of an inductor in voltage with a low-frequency power source and, therefore, helps to reduce currents in the windings.

A disadvantage of the known inductor is low efficiency. This is due to the fact that the placement of flat inductor coils with simultaneous coverage of two teeth and one groove leads to a significant increase in the average length of the coil winding, increase inductance, increase mass and electrical losses in the winding. In addition, the implementation of the coils without bending of the frontal parts, as well as with alternation in layers, leads to a low coefficient of filling the groove with copper ( _Cu -0.3-U, 4), which leads to the need to increase the depth of the grooves and entails an increase in the groove scattering of the inductor up to half of the main magnetic flux.

A known method of mixing a molten metal, including placing an electromagnetic stirrer in the form of an inductor at a distance of the working gap from the surface of the molten metal, connecting it to a power source containing a voltage converter, creating a traveling magnetic field and applying the indicated field to the molten metal (patent RU2007266, prior. 04.01 .1988, B22D 27/02). In this case, a traveling magnetic field is created with a periodic non-sinusoidal three-phase voltage (using a converter) and is used with a spectrum containing simultaneously harmonics of symmetric three-phase voltage systems of the forward and additional reverse phase sequence with amplitudes increasing with increasing frequency.

However, the described method has a low efficiency of mixing the molten metal due to the non-optimal magnitude of the pole division of the inductor. As follows from the description, the method uses a bipolar three-phase inductor, on which serves a three-phase non-sinusoidal periodic voltage with several frequencies and amplitudes. Given the indicated dimensions of the crucible (120 mm><150 mm x300 mm), the size of the working gap (D = 15 mm) and the resulting magnetic field frequencies (14.3 Hz, 28.6 Hz and 50 Hz), the used inductor ensures the penetration of the magnetic field into the molten metal to a depth of not more than a few millimeters, which does not provide mixing of all layers of the molten metal and, consequently, leads to an ingot with an inhomogeneous structure and poor mechanical properties, in particular, when the solidified part of the ingot during crystallization reaches 10 mm and proc eed.

The closest in technical essence to the claimed group of inventions is the technical solution described in the international application PCT / IB2014 / 060273 for the invention "Method and device for moving molten metal", prior. 03/28/2013, submission date 03/28/2014, B22D11 / 1 15, B22D11 / 12, B22D27 / 02, H01F7 / 20, Н02К44 / 08, Н05В6 / 34, F27D 27/00. The specified method includes placing an electromagnetic stirrer containing an inductor at a distance of the working gap from the surface of the molten metal, connecting it to a power source, creating a magnetic field with at least two pairs of magnetic poles and exposing the molten metal to said field. In this case, the connection to the power source is carried out with the adjustment of the current, voltage or phase applied to the coil groups of the inductor. A device that implements the method includes an inductor and a power source connected to it, while the inductor comprises a multiphase winding of three coil groups connected to six pairs of power switches of the inverter, that is, with the power of each coil group separately. The design of the device implements the production of at least two pairs of magnetic poles of the inductor (2p> 4) in a sequence of phases corresponding to the AYC connection diagram: the first phase (phase A) is 0 ° el., The second phase (phase U) is 60 ° el., The third phase (phase C) - 120 ° el.

A disadvantage of the known technical solution, selected as a prototype for the proposed method and an electromagnetic stirrer with a longitudinal magnetic field, is the low efficiency of mixing the molten metal, which is recognized by the authors of this invention in comparison with another embodiment of an inductor with a transverse magnetic field. This is due to the fact that two or more pairs of magnetic poles generated by the device per inductor length (2p> 4) lead to a reduction in the pole division of the inductor and, as a consequence, to a decrease in the depth of penetration of the field through increased working clearance D. Moreover, the possibility stated in the claims for creating a prototype device, for example, of three pairs of magnetic poles (2p = 6) in the absence of information about the nature of winding of coil groups and winding data of the inductor allows us to conclude that nine coil groups with inversion are used the second, fifth and seventh coil groups and the inclusion of every third coil group in phase, which also leads to a significant decrease in the efficiency of the inductor due to mismatch pole division of the inductor and the working gap D. The description of the prototype device also gives an example of an ineffective inductor with a longitudinal magnetic field of 2718 mm long for the working gap D = 500 mm and the connection diagram of the AYC windings with a phase zone of 60 ° el., but the width of the phase zone of the inductor it is overestimated by more than 30%, which leads to a critical drop in the efficiency of the inductor for the working gap D = 500 mm.

SUMMARY OF THE INVENTION

The objective of the invention is to increase the efficiency of mixing the molten metal at the lowest energy costs, reduced mass of the inductor of the electromagnetic stirrer and reduced overall dimensions.

The technical result consists in optimizing the winding data (first of all, the number of pairs of magnetic poles of the inductor and, as a consequence, the magnitude of the pole division of the inductor) for a given value of the working gap D between the inductor and the surface of the mixed metal melt and the possibility of using common industrial semiconductor power sources (with three pairs power keys of the inverter).

The technical result is achieved by the fact that in the method in which an electromagnetic stirrer is used, including an inductor connected to a low-frequency power source, the inductor is placed at a distance of the working gap D from the metal melt and create longitudinal traveling and pulsating magnetic fields, and thereby act as indicated magnetic fields on the molten metal, according to the invention, specify the phase of the current on the connected coil groups so that the pole division of the inductor by the magnetically motive force of the coils of the corresponding groups corresponded to (0.7–2.2) · D · p, the total width of the phase zones of the coil groups in magnetic fluxes was up to 400 ° el., and the fractional or odd number of pairs of magnetic poles of the inductor accounted for the active length of the inductor, but not more than 2. In special cases, the implementation of the method: - coil groups are connected to separate two pairs of power switches of the inverter of the power source;

- form magneto-motive forces of central and lateral coil groups of different phases and amplitudes so that the phase difference of the magneto-motive forces of the coil groups corresponds to 60 ° el. or 90 ° el .;

- set the phase of the current and the amplitude of the current of each coil group different from the phase of the current and the amplitude of the current of the respective adjacent coil groups;

- form a phase shift of the currents of the coil groups by the feedback signal from the magnetic flux sensors located on the teeth of the inductor;

- use an inductor with three coil groups per active length, connect each coil group to the midpoint of three separate pairs of power semiconductor switches of the inverter of the low-frequency power supply according to the “star” or “triangle” pattern and form magnetically moving forces of central and lateral coil different in phase and amplitude groups so that the width of the phase zone of each coil group in magnetomotive force corresponded or was less than 60 ° el .;

- use an inductor with four coil groups per active length, connect each coil group to the midpoint of three separate pairs of power semiconductor switches of the inverter of the low-frequency power supply according to the “star” or “triangle” pattern and set the phase currents so that the active length of the inductor falls the fractional number of pairs of magnetic poles of the inductor is 2p = 4/3, and the width of the phase zone of each coil group in magnetomotive force corresponded or was less than 60 ° el .;

- use an inductor with three coil groups per active length, connect the extreme coil groups to the midpoints of two pairs of power semiconductor keys of the inverter of the low-frequency power supply, connect the central coil group to the midpoints of the other two pairs of power semiconductor keys of the inverter of the low-frequency power supply, set the current phases to so that the active length of the inductor accounts for a fractional number of pairs of magnetic poles of the inductor 2p = 3/2, and the width of the phase zone of each coil group s on magnetomotive force corresponded to 90 ° el .;

- use an inductor with three coil groups per active length, when installed on a furnace and connected to a three-phase or two-phase power source, and depending on the number of phases of the power source, choose a coil connection scheme groups in such a way that either connect the coil groups to the midpoints of the three pairs of power semiconductor switches of the inverter of the low-frequency power supply according to the “star” or “triangle” scheme and form magnetically motive forces of central and side coil groups of different phase and amplitude so that the width of the phase zone for each coil group in terms of magnetomotive force, it corresponded, or was less than 60 ° el., or connect the extreme coil groups to the midpoints of two pairs of power switches of the low-frequency source inverter power supply, connect the central coil group to the midpoints of the other two pairs of power switches of the inverter of the low-frequency power source, set the current phases so that the active length of the inductor accounts for a fractional number of pairs of magnetic poles of the inductor 2p = 3/2, and the width of the phase zone of each coil group according to the magnetomotive force, it corresponded to 90 ° electric, for which additional electric contacts are provided on the coil groups of the inductor to adjust the load for a particular switching circuit;

- create a combination of magnetic fluxes by forming a power source on the multiphase winding of a periodic voltage containing a spectrum of the main harmonic and additional harmonics of symmetric three-phase voltage systems of direct or reverse sequence;

- carry out the action cyclically, while the cycle includes one change in the direction of movement of the traveling magnetic field, and in each cycle, after changing the direction of movement of the traveling magnetic field, the frequency and magnitude of the voltage across the multiphase winding are changed;

- the duration of exposure to a running magnetic field in one direction is 2-4 minutes;

- use a low-frequency power supply containing a rectifier based on SE modules, when creating a longitudinal traveling and pulsating magnetic fields, control the pulse sequence for each arm of the IGBT module for the entire period, which are consistent with the control pulses of the inverter based on the SE modules;

- use a low-frequency power supply containing an inverter based on SE modules, when creating a longitudinal traveling and pulsating magnetic fields, pulses with a pulse-width modulation (PWM) frequency of less than 1000 Hz are controlled. The technical result is also achieved by the fact that in the first embodiment of the implementation of the electromagnetic mixer of the molten metal for implementing the method comprising an inductor and a low-frequency power source connected to it, the inductor has an open core with teeth and a multiphase winding of three coil groups located in the grooves between the teeth core with coverage of the back of the core, according to the invention, the number of turns of the extreme coil groups is greater than the number of turns of the central coil group, the central coil The target group is inverted relative to the extreme coil groups due to the direction of winding or connection, and the coil groups are connected in a star or triangle pattern and connected to the midpoints of three pairs of power switches of the power source inverter. In special cases, the execution of the first version of the electromagnetic stirrer:

- contains at least two additional coil groups located on the core after the extreme coil groups relative to the middle of the core;

- the teeth of the core are made wider than the back of the core;

- the core rod has a longitudinally variable cross-section;

- the back of the core is made of electrical steel, and the teeth are made of structural steel;

- the power supply on the DC bus contains a capacitance of more than 30 mF;

- the inductor is connected to a low-frequency power supply with a shielded power cable with an even number of conductors, with half of the conductors connected to the beginning of the coil groups, and the other half of the conductors connected to the end of the coil groups.

The technical result is also achieved by the fact that in the second embodiment of the electromagnetic mixer of the molten metal for implementing the method, comprising an inductor and a low-frequency power source connected to it, the inductor includes an open core with teeth and a multiphase winding of at least three coil groups located in grooves between the teeth of the core with the coverage of the back of the core, according to the invention, the extreme coil groups are connected sequentially and counterclockwise, while the number of turns of cr the lower coil groups are less than or equal to the number of turns of the central coil groups, and even coil groups are inverted along the length of the core relative to the odd ones reel groups due to the direction of the winding or wiring diagram. In special cases, the execution of the second version of the electromagnetic stirrer:

- the teeth of the core are made wider than the back of the core;

- the inductor includes three coil groups, the inverter of the power source contains four pairs of power switches, while the central coil group is connected to the midpoints of the first two pairs of power semiconductor switches, and the extreme coil groups are connected to the second two pairs of power switches;

- the inductor has four coil groups connected to the midpoints of three pairs of power switches of the inverter of the low-frequency power supply according to the “triangle” scheme, while the extreme coil groups are connected to one shoulder of the “triangle”, the second coil group along the length of the core is connected to the second shoulder of the “triangle” ”, And the third coil length along the core is connected to the third arm of the“ triangle ”;

- the inductor contains four coil groups connected to the midpoints of three pairs of power switches of the inverter of the low-frequency power supply according to the “star” scheme, while the extreme coil groups are connected to one phase of the “star”, the second coil group along the length of the core is connected to the second phase of the “star” ”, And the third coil length along the core is connected to the third phase of the“ star ”, and the zero point of the“ star ”is connected to the midpoint of two capacitors connected in series on the low-frequency DC bus and power source;

- the core rod has a longitudinally variable cross-section;

- the cross section of the Central part of the core core, on which the central coil groups are located, is larger than the cross section of the extreme parts of the core, on which the extreme coil groups are placed;

- the power source contains an active controlled rectifier based on power UVT-modules;

- the power supply on the DC bus contains a capacitance of more than 30 mF; - the inductor is connected to a low-frequency power supply with a shielded power cable with an even number of conductors, with half of the conductors connected to the beginning of the coil groups, and the other half of the conductors connected to the end of the coil groups.

The inventors have found that the efficiency of mixing a metal melt at the lowest energy, mass, and overall dimensions depends on the choice of optimal winding data corresponding to the magnitude of the working gap D between the inductor and the surface of the mixed metal melt, if it is possible to use common industrial semiconductor frequency converters as power sources for an electromagnetic mixer . According to the method, the optimization of the winding data is ensured by selecting a combination of a circuit for connecting coil groups to a power source and supplying current phases depending on a given value of the working gap D. Thus, the authors experimentally established that the claimed range of the total width of the phase zones of the coil groups by magnetic flux on the teeth crowns ( up to 400 ° el.) is optimal for obtaining the maximum electromagnetic force of the inductor F _T with a different number of pairs of magnetic poles of the inductor.

The claimed range of the pole division of the inductor by the phases of the magnetomotive force of the coil groups of the inductor t = (0.7-2.2) · D · p allows you to ensure the magnitude of the electromagnetic force of at least 50% of the maximum force at the optimal value of the pole step, and the range t = ( 0.95-1.7) · D · p - not less than 75%.

In addition, the authors revealed that for a working gap of D = 550 mm, the optimum magnitude of the pole division of the inductor t in magnetic fluxes will be about 120CH – 1250 mm, and in magnetomotive force - 2150 mm. This means that with an inductor length of 2000 mm it is more rational to use a three-zone inductor (with three coil groups) with an AZB connection circuit or a four-zone inductor (with three coil groups) with an AZBC connection circuit, which follows from FIG. 23, FIG. 25, FIG. 27, obtained by the authors of the claimed invention as a result of mathematical modeling of the inductor. For a working gap of D = 700 mm, the optimal magnitude of the pole division of the inductor in terms of magnetomotive force is 2400 mm (see Fig. 24, Fig. 26, Fig. 28). It can be seen from the figures that for the considered working gaps of 550 mm and 700 mm, the inductor with four coil groups according to the ABCU switching circuit (2p = 2) is significantly inferior to all versions of the inductor with an odd and fractional number of pairs of magnetic poles AZB (2p = 1), AZBC (2p = 4/3), ABX (2p = 3/2). The listed switching circuits AZB, AZBX, ABX suggest connecting to a symmetrical voltage system with a phase shift between adjacent coil groups along the length of the inductor 60 ° el. for three-phase execution (schemes AZB and AZBX) and for two-phase execution 90 ° el. (scheme ABX). But if you connect each coil group of the inductor to the midpoints of two separate pairs of power semiconductor switches of the inverter of the low-frequency power source and independently control the phases of the currents in each coil group, then you can set any other value of the angle of the phase shift of the currents in adjacent coil groups. This allows you to set the optimal value of the pole division of the inductor by magnetic flux with the available length of the inductor and the connection scheme of the coil groups, for example, when the working clearance D.

The implementation of the method of mixing the molten metal is provided by the use of an electromagnetic mixer according to any of two options. So, the features of performing a multiphase winding (the number of coil groups from 3 to N or the scheme of their connection with each other (splitting into parts of one of the phases of a multiphase winding) and the execution of coil groups inverted due to the direction of winding or the connection circuit provides a fractional and odd number of pairs magnetic poles per active inductor length, and the use of coil groups with a different number of BHTKOBW ,, where i = l, ..., N is the number of coil groups, ensures the symmetry of their resistance for different connection diagrams for pairs of power switches, which together leads to obtaining optimal winding data of the inductor for varying the working gap D. The fractional and odd number of pairs of magnetic poles per active length of the inductor, in turn, allows you to generate the total value of the phase zones of the coil groups by magnetic fluxes less than 400 ° el., which also helps to obtain optimal winding data of the inductor based on the size of the working gap D. In FIG. 15 is a vector diagram of the magnetomotive forces (MDS) of the coil groups of a multiphase winding and the magnetic fluxes of the teeth through the area of the active surface of the tooth (or on the crowns of the teeth). In the MDS diagram, coil groups with phases A, B, X, and Y are represented by magnetic fluxes Fi, F ₂ , F _3, and F ₄ shifted by 90 ° el. In this case, adjacent magnetic fluxes on the active surface of the teeth Fi, Ф ₂ , Фз, Ф ₄ , Ф _{5 are} shifted relative to each other not by 90 ° el., But by different angles from 83 ° el. up to 128 ° el., and the total angle of shift between the angles of the magnetic fluxes Fi and Ф ₅ is 412 ° el. For the schemes AZB (2p = 1), AZBX (2p = 4/3) and ABX (2p = 3/2) the phase angle of the magnetic flux will be respectively about 276 ° el. (see Fig. 4), 323 ° el. (see Fig. 9), 350 ° el. (see Fig. 12). The difference in the phase shift angle in MDS from the width of the phase zone of a planar inductor in magnetic flux is due to the presence of edge effects and a relatively small number of magnetic poles per length. Based on the fact that the total magnitude of the phase zones of the coil groups by magnetic flux does not coincide in magnitude with the total magnitude of the phase zones by MDS, the width of the magnetic pole of the inductor can be determined by the MDS of the coil groups t = // 2p or by the total magnitude of the phase zones of the coil groups of

magnetic fluxes t = - -—, where c is the total value of the phase zones of the coil

groups of magnetic flux or phase shift of the magnetic flux in the first and last prong along the length of the inductor. Physically, the phase shift can be determined on a real inductor using magnetic flux sensors or measuring coils on the crowns of the teeth. Thus, the width of the magnetic pole in magnetic flux for an inductor 2000 mm long with the inclusion of coil groups according to the schemes AZB (2p = 1), AZBC (2p = 4/3), ABX (2p = 3/2) and ABCU (2p = 2) will be equal to about 1304 mm, 1114 mm, 1028 mm, 874 mm, respectively.

The supply of the device with additional coil groups, the implementation of the core rod with a longitudinally cross-sectional cross-section, in particular with an increased cross-section of the central part of the rod compared to the extreme parts of the rod, reduces the influence of edge effects on the magnetic field in the melt and increases the efficiency of the inductor as a whole . The implementation of the teeth wider than the back causes an increase in the active width of the inductor and, consequently, the expansion of the zone of influence of the magnetic field, which further contributes to an increase in the mixing efficiency.

In a flat machine, the magnitude of the total magnetic flux along the back of the core will be unequal along the length of the back of the core (more under the central coil groups and less under the extreme coil groups), so the cross section of the back of the core is larger under the central coil groups and less under the extreme in length, which allows to achieve reducing the mass of the inductor, the consumption of active materials and copper losses of the extreme coils.

The electromagnetic stirrer inductor is an inductive load for the power source and operates at a frequency close to 1 Hz. The lower the frequency of the PWM on the SWT modules of the inverter of the power source, the lower the voltage loss at the higher harmonics, the greater the current in the inductor winding, the less the loss in the SWT modules of the inverter, it heats up less. Therefore, the PWM frequency for inductors is selected less than 1 kHz and, often, close to 100 Hz.

The most loaded part of the core with the maximum magnitude of magnetic fluxes is the back of the core, and the less loaded ones are the teeth. Considering that magnetic flux conducts magnetic flux to the best extent, which is also characterized by low losses in steel, but which is quite expensive, it is more preferable to make the core core of electrical steel and the teeth of structural steel, which together leads to maximum efficiency and minimization of costs to manufacture the core of the inductor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a general view of a furnace with an electromagnetic mixer of molten metal;

FIG. 2 is a general view of a crystallizer with an electromagnetic mixer of a metal melt (during crystallization);

FIG. 3 - inductor with three coil groups in length and winding data of a multiphase winding m = 3, 2p = 1, Z = 3, q = l, a = 60 ° el. with a vector diagram of the magnetomotive forces of the coil groups;

FIG. 4 shows the distribution of magnetic fluxes of an inductor with three windings along the length of FIG. 3 in a three-phase design (an inductor with a split winding) and a vector diagram of the magnetomotive forces of the coil groups (Fi, F ₂ , F ₃ ) and magnetic fluxes (Fi, F ₂ , Fz, F4) on the crowns of the teeth of the core;

FIG. 5 - a connection diagram of an inductor with three coil groups per length according to the AZB scheme according to the “star” scheme with inversion of the winding direction (a) and inversion of the winding connection (b);

FIG. 6 - connection diagram of an inductor with three coil groups per length according to the AZB scheme according to the “triangle” scheme with inversion of the winding direction (a) and inversion of the winding connection (b);

FIG. 7 - inductor with three main coil groups in length and winding data of a multiphase winding m = 3, 2p = 1, Z = 3, q = l, a = 60 ° el. and two additional reel groups;

FIG. 8 - inductor with three coil groups in length and winding data of a multiphase winding m = 2, 2p = 3/2, Z = 3, q = l, a = 90 ° el. with a vector diagram of the magnetomotive forces of the coil groups; FIG. 9 shows the distribution of magnetic fluxes of an inductor with three windings along the length of FIG. 8 in a two-phase design (split-coil inductor) and a vector diagram of the magnetomotive forces of the coil groups (F _ls F ₂ , F ₃ ) and magnetic fluxes (Fi, Ф ₂ , Ф ₃ , Ф ₄ ) on the crowns of the teeth of the core;

FIG. 10 is a connection diagram of an inductor with three coil groups per length according to the AVX scheme of FIG. nine;

FIG. 1 1 - an inductor with four main coil groups per length and winding data of a multiphase winding m = 3, 2p = 4/3, Z = 3, q = l, a = 60 ° el. with a vector diagram of the magnetomotive forces of the coil groups;

FIG. 12 shows the distribution of magnetic fluxes of an inductor with four windings over the length of FIG. 1 1 in a three-phase design (an inductor with a split winding) and a vector diagram of the magnetomotive forces of the coil groups (F _t , F ₂ , F ₃ , F ₄ ) and magnetic fluxes (Fi, Ф ₂ , Ф ₃ , Ф ₄ , Ф ₅ ) on core tooth crowns;

FIG. 13 is a connection diagram of an inductor with four coil groups per length according to the AZBC scheme of FIG. eleven ;

FIG. 14 - inductor with four main coil groups per length and winding data of a multiphase winding m = 2, 2p = 2, Z = 4, q = l, a = 90 ° el. with a vector diagram of the magnetomotive forces of the coil groups;

FIG. 15 shows the distribution of magnetic fluxes of an inductor with four windings along the length of FIG. 14 in a two-phase design (a split-coil inductor) and a vector diagram of the magnetomotive forces of coil groups (Fi, F ₂ , F ₃ , F ₄ ) and magnetic fluxes (Fi, F ₂ , F ₃ , F ₄ , F ₅ ) on the teeth crowns core;

FIG. 16 is a connection diagram of an inductor with three coil groups per length according to the AZBC scheme of FIG. fourteen;

FIG. 17 is a circuit diagram of a frequency converter with a rectifier, a DC link and an inverter based on three pairs of power switches (Ai, A ₂ , A ₃ );

FIG. 18 - voltage inverter of the frequency converter based on six pairs of power switches (Ai, A ₂ , A ₃ , A ₄ , As, A ₆ ) and the inclusion of a three-phase three-zone inductor according to the scheme with parameters m = 3, 2p = 1, Z = 3, q = l, a = 60 ° e .;

FIG. 19 is an electrical diagram of a frequency converter with a rectifier, a DC link and an inverter based on three pairs of power switches (Ai, A ₂ , Az) and the inclusion of a three-phase three-zone inductor in a star according to a circuit with parameters w = 3, 2p = 1, Z = 3 , q = l, a = 60 ° e .; FIG. 20 is a circuit diagram of a frequency converter with a rectifier, a DC link and an inverter based on three pairs of power switches (Ai, A ₂ , A ₃ ) and the inclusion of a three-phase three-zone inductor in a triangle;

FIG. 21 - voltage inverter of the frequency converter based on three pairs of power switches (Ai, A ₂ , A ₃ ) And turning on the three-phase four-zone inductor according to the scheme with parameters m = 3, 2p = 4/3, Z = 4, q = l, and = 60 ° el .;

FIG. 22 - voltage inverter of the frequency converter based on four pairs of power switches (Ai, A ₂ , Az, A ₄ ) and the inclusion of a two-phase three-zone inductor according to the scheme with parameters w = 2, 2p = 3/2, Z = 3, q = l, a = 90 ° el .;

FIG. 23 - dependence of the tangential force of the electromagnetic stirrer on the melt in the furnace for four options for connecting windings depending on the length of the inductor with a working gap of 550 mm;

FIG. 24 - dependence of the tangential force of the electromagnetic stirrer on the melt in the furnace for four options for connecting windings depending on the length of the inductor with a working gap of 700 mm;

FIG. 25 - dependence of the ratio of the tangential force of the electromagnetic stirrer on the melt in the furnace to the mass of the inductor for four options for connecting windings depending on the length of the inductor with a working gap of 550 mm;

FIG. 26 - dependence of the ratio of the tangential force of the electromagnetic stirrer on the melt in the furnace to the mass of the inductor for four options for connecting windings depending on the length of the inductor with a working gap of 700 mm;

FIG. 27 - dependence of the ratio of the tangential force of the electromagnetic stirrer on the melt in the furnace to the consumed active power for four options for connecting windings depending on the length of the inductor with a working gap of 550 mm;

FIG. 27 - dependence of the ratio of the tangential force of the electromagnetic stirrer on the melt in the furnace to the consumed active power for four options for connecting windings depending on the length of the inductor with a working gap of 700 mm;

FIG. 28 - dependence of the ratio of the tangential force of the electromagnetic stirrer on the melt in the furnace to the consumed active power for four options for connecting windings depending on the length of the inductor with a working gap of 700 mm; FIG. 29 - dependence of the tangential force of the electromagnetic stirrer on the melt in the furnace on the phase shift angle of the magnetomotive forces of adjacent coil groups for three (N = 3) and four (N = 4) coil groups of the inductor with a length of 2200 mm and a working gap of 550 mm;

FIG. 30 - the optimal value of the inductor and the pole division of the inductor at 2p = 1 of the working gap D.

DETAILED DESCRIPTION OF THE INVENTION

To implement the inventive method, an electromagnetic stirrer is used in one of two versions, which includes a flat inductor 1 connected to a power source 2. The inductor 1 contains a core 3 with teeth with a back 4 core and teeth 5 and a multiphase winding 6 in the form of several coil groups 6.1. .. 6.N, where N is the number of coil groups. The core 3 is made of sheets of electrical steel or structural steel.

Multiphase winding is a coil group 6, each of which in turn consists of several flat concentric coils of copper wire, formed by winding on the back 4 of the core 3 in the grooves between the teeth 5 of a width of 2C, which can be made wider than the back 4 of the core. The cooling of the multiphase winding can be performed by air (using an air cooling system 7, Fig. 1 and Fig. 2) or water (by supplying coolant to a copper tube from which coils can be made).

The power supply 2 consists of an input link, a rectifier 12 (in particular, based on thyristors for a passive rectifier (Fig. 17) or power IGBT modules for an active rectifier), a DC link 13 (capacitive at least 24 mF and inductive filters and break -module) and inverter 14. The power supply 2 is connected to the inductor by a power cable 8. The cable can be shielded with earth and an even number of conductors, with half of these conductors connected to the beginning of coil group 6 and the other half of The connected conductors are connected to the end of coil group 6. Such a connection reduces the amount of interference from cable 8 from current to other objects, for example, nearby signal cables and magnetic sensors.

According to the first embodiment of the electromagnetic mixer of the coil groups, there can be three or more (3.4 ... N), and the extreme coil groups 6.1 and 6.N are connected in series and counterclockwise, the number of their turns Wi and W _{N is} less than or equal to the number of central turns coil groups 6.2 ... 6.N-1, and even lengths of the core 3 coil groups are inverted relative to the odd coil groups due to the direction of the winding or wiring diagram.

According to the second embodiment of the electromagnetic stirrer of coil groups 6, only three were used (Z = 3), the extreme coil groups 6.1 and 6.3 have a larger number of BHTKOBWI AND W ₃ than the central coil group 6.2 with the number of turns W ₂ , the central coil group is inverted relative to the extreme coil groups due to the direction of the winding or connection diagram, and the coil groups are connected according to the “star” or “triangle” pattern and connected to the midpoints of three pairs of power switches of the inverter of the power supply 2.

According to the claimed method, the electromagnetic stirrer according to one of the above embodiments is installed at a distance of the working gap D from the surface of the molten metal 9, under the hearth of the furnace 10 (Fig. 1) or the side wall of the bath, the furnace is the distance of the working gap D, or near the wall of the crystallizing ingot 11 under the mold 12 in a casting machine with a working gap D between opposite inductors and is connected to a low-frequency power supply 2 according to a given scheme. When you turn on the low-frequency power supply 2 in the multiphase windings of the inductor 1, a low-frequency electric current appears, while the phases of the current are set so that the pole division t of the inductor by the magnetomotive force of the coil groups 6 corresponds to (0.7-2.2) · D · p, the total width of the phase zones of the coil groups ys in magnetic fluxes was up to 400 ° el., and the active / inductor length accounted for a fractional or odd number of pairs of magnetic poles of the inductor. The current displaced in space and time in the windings creates a longitudinal traveling and pulsating magnetic field, which acts on the molten metal 9 in the bath of the furnace 10. The distribution of magnetic fluxes of each of the windings is limited by the pole pitch t '. The resulting magnetic flux of the inductor 1 is formed by the magnetic fluxes of all the windings of the inductor 1, as shown in FIG. 4. The magnetic flux Фд pulsates in the radial direction from the axis of the coil A - X, Фв - the axis of the coil B - U, Фс - the axis of the coil C - Z. In this case, the teeth 5 of the core 3 serve as magnetic field concentrators and direct most of the pulsating magnetic fluxes direction of the molten metal 9. The magnetic fluxes directed along the winding axis are closed along the back 4 of the core and teeth 5 of the core 3, along the working gap D and directly along the molten metal 9. The resulting magnetic flux forms a traveling magnetic field, the wave of which moves along the ind axis Ktorov with velocity Vi = 2-Tf, where t - the value of the inductor pole pitch, f - frequency of the supply voltage inductor 1. The magnetic fluxes of each of the windings are closed within one pole division. An alternating magnetic flux penetrates the molten metal 9, inducing an electromotive force (EMF), which, in turn, leads to the appearance of current. The interaction of alternating magnetic flux and currents in the molten metal 9 creates electrodynamic forces (normal R _p and tangential F _T PO with respect to the surface of the melt at the inductor installation site) and sets the molten 9vanny furnace 10 in motion, providing the desired technological effect - homogenization of the molten 9 in chemical composition and temperature, as well as the acceleration of melting of the solid mixture.

Each of the windings is covered not only by its own magnetic field, but also by the magnetic fluxes of the remaining windings within the same pole division. So, for example, in the inductor 1 in FIG. 4, in the first tooth 5 of core 3, the magnetic flux of the phase A winding and part of the magnetic fluxes of phases B and C are summed, and the total flux Fi is formed. In the remaining teeth 5, a similar picture is observed. The fluxes F _I ... F _N + _I on the crowns of the teeth 5 do not include the scattering fluxes, which form a significant part for the inductor 1 with windings 6 wound through the back 4 of the core 3. The magnitude of the magnetic flux determines the magnetic induction of the core material 3 and the relative magnetic permeability, as well as inductive resistance of the windings 6. With an equal linear current load of the inductor 1, the magnitude of the magnetic flux of different sections of the core 3 is different and is determined by the winding data of the multiphase winding 6 of the inductor 1, phases and amp currents in the coil group. The magnitude of the magnetic flux will be determined by the magnitude of the MDS of the coil groups, the degree of saturation of the magnetic circuit and the ratio of the magnitude of the working gap D and the magnitude of the pole division of the inductor. In FIG. Figure 4 on the left shows a vector diagram of the MDS of coil groups and magnetic fluxes at the output of tooth 5 for an inductor with three coil groups per length and the number of pairs of magnetic poles AZB. The phase shift between the MDS in the vector diagram is 60 ° el. And the flows at the exit from the teeth Фц Ф ₂ , Фз and Ф _{4 are} shifted by greater degrees than 60 ° el., And in total are about 276 ° el., Which occurs due to the openness of the core of the planar inductor and edge effects.

In addition to the fact that the fluxes within the pole division of the inductor are added, the electromagnetic processes in the inductor are affected by the effect of power transfer between the windings of different phases of the multiphase winding 6, which is due to the mutual inductance of the windings of different phases and a small number of poles, when the coil groups of different phases are in unequal conditions along the length of the core 3 with a small number of poles due to the unequal mutual position of the coil groups, which ultimately leads to a significant asymmetry of the load in the form of a low-pole flat inductor for the power source. For example, for a three-zone inductor with phase rotation in the AZB coil groups (see Fig. 3), the following system of equations for the multiphase winding voltages will be characteristic:

where UA, UB, He are the voltage of the windings of phases A, B, C;

IA, IB, IC - currents in windings from phases A, B, C;

GA, g in, rc - active resistances of phases A, B, C;

ХА, ХВ, Х _С - reactance of phases A, B, C;

ХАВ, ХВС, ХСА - mutually inductive resistances of windings of different phases.

Due to the fact that the mutual inductances х _А в and хвс are significantly higher than the mutual inductance ХС _А in this system, when the inductor is switched on to a symmetric EMF system with equal amplitude and 120 ° el shifted. phases of voltages, current phases differ significantly from 120 ° el. due to the presence of mutual inductance. A more symmetrical system of currents, MDS and magnetic fluxes can be created using two separate pairs of power semiconductor switches for each coil group with the ability to set a certain amplitude and voltage phase, taking into account the mutual inductance of different phases, longitudinal and edge effects in a flat inductor. However, this method leads to asymmetry of stresses and limits the magnitude of stresses for a given load.

The proposed inductors with split windings according to the connection diagrams AZBX (see Fig. 11) and ABX (see 8) represent a much more symmetrical load than a three-zone inductor according to the AZB circuit (see Fig. 3). The fact is that the two coil groups at the ends of the rod along the length, connected in series and in the opposite direction, have the same current, but the two coil groups of phase A are equally affected by the magnetic fluxes of phases B and C, but since they are in antiphase, then the power transferred to one coil group is equal in magnitude but opposite in phase than that transferred to another. That is, extreme power transfer coil groups compensates each other for the two parts of the phase A winding. And the system of equations for the four-zone inductor with phase rotation in the AZBX coil groups (see Fig. 11) will look like:

Obviously, the system of equations (2) corresponds to a significantly more symmetric load than the system of equations (1). Therefore, split-coil inductors are significantly more profitable than inductors according to the AZB scheme in terms of symmetry, stabilization of operation and operating conditions of the power source.

To improve the symmetry of currents in a three-phase inductor do not care. 3 can be achieved by performing an unequal number of turns of the phases W, which leads to the result shown in FIG. 4, and the possibility of connecting the inductor 1 to a common industrial frequency converter for standard induction motors. In this case, the capacitance on the DC bus of the frequency converter must be selected in such a way as to ensure an emergency stop of the electromagnetic stirrer in emergency braking mode without critical overvoltage on the DC bus capacitors.

When connecting each individual coil group to two separate pairs of power semiconductor switches, it is possible to adjust the phase shift in the MDC of adjacent coils to match the magnitude of the pole division of the inductor by magnetic flux with the length of the inductor, the number of coil groups and the size of the working gap, as shown in FIG. . 29. For a three-zone and four-zone inductor, there is an optimal value for the phase shift between the windings of the adjacent windings, which ensures maximum melt force. A variant of connecting a three-zone inductor with three coil groups for a length of six pairs of power semiconductor switches is shown in FIG. 18, where three coil groups are connected to three standard inverter power assemblies with three pairs of power switches Ai, where i = l _ 6 is the number of the pair of power switches VT _j . There is a way to obtain maximum melt force and load symmetry of the power source when setting rational MDS coil groups by providing a given shift phases of currents of coil groups along the length of the inductor by a feedback signal from magnetic flux sensors located on the teeth of the inductor.

Also, by setting the unequal amount of phase shift in adjacent coil groups along the length, the input and output edge effects can be partially compensated. You can also compensate for these effects by placing additional coil groups along the length of the core at its beginning and end, as shown in FIG. 7.

The best solution is to choose such an inductor length for a given working gap in order to obtain maximum melt forces at standard MDS phase angle angles of 60 ° el. Such inductor lengths are shown for various operating clearances shown in FIG. 30. In this case, a three-phase inductor can be connected to a common industrial semiconductor frequency converter (Fig. 17), for example, according to the circuit for a three-zone inductor (see Fig. 19, Fig. 20, Fig. 22) or for a four-zone inductor for the AZBX circuit - FIG. 21.

MODES FOR CARRYING OUT THE INVENTION

The claimed group of inventions was tested using various methods, including on physical models of electromagnetic stirrer options on a scale of 1: 10, on a test site with an inductor acting on a load cell and in the form of existing pilot plants installed on existing furnaces and mixers. The most reliable information on the effectiveness of electromagnetic mixing can be given by analyzing a series of samples from the furnace after a certain time using the theory of experimental design in metallurgy. However, conducting such studies on several device modifications is difficult. In this regard, the evaluation of the efficiency of mixing the molten metal was carried out by assessing the mixing speed of the melt in the magnetic field of the inductor, the integral force F _T on the melt, the ratio of the tangential force to the power of the inductor and to the mass of the inductor (F _T / Рда F _{T /} m,), which were obtained as a result of calculations, measurements of the operation of the electromagnetic stirrer at idle and by affecting the load cell and only in some cases were verified by the time of dissolution of the ligature additives in existing m Photocopier.

The main implemented options are presented in table 1 and table 2 for an inductor 2200 mm long with a working gap of 550 mm and an inductor 2500 mm long with a working gap of 700 mm, respectively. Inductors 2200 mm and 2500 mm long are made with multiphase windings with four coil groups and three reel groups. The magnitude and phase of the currents was set separately for each coil group from the power source with two separate pairs of power semiconductor switches. The melt velocity in the zone of action of the magnetic field of the inductor is determined by calculation, since there are currently no reliable methods for determining the flow velocity of high-temperature and aggressive molten aluminum in the furnace.

An analysis of the data in Tables 1 and 2 shows that, with a working gap of D = 550 mm, it is optimal to use an electromagnetic stirrer that provides a fractional number of pairs of magnetic poles per active inductor length, namely 2p = 4/3 with an AZBC connection diagram, with a working gap D = 700 mm optimal is the use of an electromagnetic stirrer, providing an integer number of pairs of magnetic poles per active length of the inductor, namely 2p = 1 with the connection circuit AVX. An inductor of length f = 2200 mm with a number of pairs of magnetic poles 2p = 4/3 with an AZBC connection diagram at a working gap of D = 550 mm showed a tangential force of 647 N and a melt velocity in the magnetic field of the inductor of 2.48 m / s. The ratio of the tangential force to the power of the inductor 8.32 N / kW and the ratio of the tangential force to the mass of the inductor 134 N / t show the greatest efficiency compared to other versions of the multiphase winding. The value of "the ratio of pole division to the value of p · D" equal to 0.95 is included in the claimed range from 0.7 to 2.2. The option with 2p = 2 and the connection circuit ABCU has t / (p · D) = 0.64, which is outside the range of 0.7-2, 2 and has low characteristics.

Table 1 - Examples of carrying out the invention when performing an inductor 2200 mm long with a working gap of 550 mm

Table 2 - Examples of the invention when performing an inductor with a length of 2500 mm with a working clearance of 700 mm

An inductor of length f = 2500 mm with a number of pairs of magnetic poles 2p = 1 with an AZB connection diagram at a working gap of D = 700 mm showed a tangential force of 585 N and a melt velocity in the area of the magnetic field of the inductor of 2.62 m / s. The ratio of tangential force to inductor power of 7 N / kW and the ratio of tangential force to inductor mass of 74 N / t show the greatest efficiency in comparison with other versions of the multiphase winding. The value of “the ratio of pole division to the value of p · D” equal to 1.14 is included in the claimed range from 0.7 to 2.2.

Placement of an inductor with a length of f = 2500 mm with the number of pairs of magnetic poles 2p = 1 with an AZB connection scheme at a working gap of D = 550 MM does not allow to obtain an increase in the melt velocity in the zone of action of the magnetic field of the inductor relative to an inductor of length I = 2200 mm with the number of pairs of magnetic poles 2p = 4/3 with the AZBC connection diagram, but it will reduce the parameters “ratio of tangential force to inductor power” and “ratio of tangential force to inductor mass” because the force on the melt under the influence of the inductor and the melt speed in the magnetic field inductor field will not increase. This is due to the fact that for each design of the inductor there is a certain limit on the possible melt speed and, therefore, the force acting on the metal melt when using a flat running longitudinal magnetic field inductor, which is a linear induction motor, decreases. Therefore, an inductor of length f = 2200 mm with a number of pairs of magnetic poles 2p = 4/3 with an AZBC connection scheme is considered optimal and sufficient for electromagnetic mixing of the melt in a furnace with a working gap of D = 550 mm, although, if the dimensions of the inductor allow, an inductor can be used length I = 2500 mm and more.

Inductors in connection circuits AZB and AZBC were switched on not only from a power supply with two separate pairs of power semiconductor switches, but also from common industrial semiconductor power supplies with three pairs of power semiconductor switches according to “star” and “triangle” circuits, which in some cases reduced or increased tangential force on the measuring stand due to changes in the phase shift a from 60 ° el. up to 49-52 ° e., which in some cases were closer or further from the optimal values, but generally not changing the overall picture.

Using the method of mixing the molten metal and the design options of the electromagnetic stirrer improves the efficiency of mixing the molten metal at the lowest energy cost, low mass of the inductor of the electromagnetic stirrer and its overall dimensions due to the optimization of winding data for a given value of the working gap D between the inductor and the surface of the mixed molten metal, if possible use of general industrial semiconductor power supplies. LIST OF ABBREVIATIONS AND DESIGNATIONS

D is the distance between the active surface of the inductor and the stirred melt (working gap);

m is the number of phases of the multiphase winding of the inductor;

p is the number of pairs of poles of the inductor;

2p is the number of poles of the inductor;

Z is the number of teeth of the core;

q is the number of grooves of the core per pole and phase;

a - phase zone of the inductor (according to the phase difference of the currents in adjacent coil groups); c is the width of the phase zone of the inductor by the total magnetic flux to the inductor dyne;

Xs = ci + ci + · · + C _N , where N is the number of inductor coil groups — the sum of the widths of the phase zones of the magnetic flux of the coil groups;

t is the magnitude of the magnetic pole division of the inductor according to the MDS is determined by the expression t = // 2p;

t 'is the magnitude of the magnetic pole division of the inductor, at which the magnetic flux on the crowns of the teeth changes by 180 ° el., which for an inductor with an odd and fractional number of magnetic poles is determined by the expression t = 180 ° el. / xs;

Q is the number of coils in the phase zone of the inductor;

b is the relative pitch of the multiphase winding;

Wi is the number of turns of the coil group number i;

k _cu ^is the fill factor of the groove with copper;

V 1 - synchronous speed of the running magnetic field of the inductor;

cob - winding coefficient;

2c is the active width of the inductor;

I is the active length of the inductor;

Aa-xx - designation of the beginning and end of the phase A winding, equal to 0 ° el .;

Bb-Yy - designation of the beginning and end of the phase B winding, equal to 120 ° el .;

CC-Zz - designation of the beginning and end of the phase C winding, equal to 240 ° el .;

AZB (analogue of AYC) - connection diagram for three coil groups of a three-phase inductor with a phase zone width of 60 ° el .;

AZBX - connection diagram of four coil groups of a three-phase inductor with a phase zone width of 60 ° el .; ABX - connection diagram of three coil groups of a two-phase inductor with a phase zone width of 90 ° el .;

ABXY - connection diagram of four coil groups of a two-phase inductor with a phase zone width of 90 ° el .;

F _T is the total tangential force of the traveling magnetic field on the melt in the furnace, the projection of the force on the axis, which coincides with the traveling magnetic field;

F _n - total normal force of the alternating magnetic field on the melt in the furnace, the projection of the force on the axis normal to the wall with the melt at the installation site of the inverter;

nor is the mass of the inductor;

Pi is the installed power of the inductor;

MDS - magnetomotive force;

EMF - electromotive force;

PWM - pulse width modulation;

Bl, B2, VZ - diode-thyristor modules of the rectifier of the power source;

VS1, VS2, VS3 - thyristors;

VD1. VD2. VD3 - diodes;

Lf - inductor on the DC bus;

Cf — capacitor on the DC bus;

VT7 - power switch for controlling energy dissipation on a braking resistor;

Rb is a braking resistor;

Al, A2, AZ - a pair of semiconductor keys of the inverter;

VT1 ... VT6 - inverter semiconductor switch.

Claims

CLAIM

1. A method of mixing a molten metal, in which an electromagnetic stirrer is used, including an inductor connected to a low-frequency power source, the inductor is placed at a distance of the working gap D from the surface of the molten metal and a longitudinal traveling and pulsating magnetic field is created, and the indicated magnetic fields act on the molten metal characterized in that the phases of the current are set to connected coil groups so that the pole division of the inductor by the magnetomotive force of the coil groups corresponded to (0.7-2.2) · D · p, the total width of the phase zones of the coil groups in magnetic fluxes was up to 400 ° el., and the fractional or odd number of pairs of magnetic poles of the inductor accounted for the active length of the inductor, but not more than 2 .

2. The method according to p. 1, characterized in that the coil groups are connected to a separate two pairs of power switches of the inverter of the power source.

3. The method according to p. 2, characterized in that they form magnetically-different forces of the central and lateral coil groups of different phases and amplitudes so that the phase difference of the magnetically-moving forces of the coil groups corresponds to 60 ° el. or 90 ° email.

4. The method according to p. 2, characterized in that the phase of the current and the amplitude of the current of each coil group are set different from the phase of the current and the amplitude of the current of the respective adjacent coil groups.

5. The method according to p. 2, characterized in that they form a phase shift of the currents of the coil groups on the feedback signal from the magnetic flux sensors located on the teeth of the inductor.

6. The method according to p. 1, characterized in that they use an inductor with three coil groups per active length, connect each coil group to the midpoint of three separate pairs of power semiconductor switches of the inverter of the low-frequency power source according to the “star” or “triangle” pattern and form Magnetomotive forces of central and lateral coil groups of different phases and amplitudes, so that the width-phase zone of each coil group is magnetically motive or less than 60 ° e.

7. The method according to p. 1, characterized in that they use an inductor with four coil groups per active length, connect each coil group to the midpoint of three separate pairs of power semiconductor switches of the inverter of the low-frequency power source according to the “star” or “triangle” pattern and set phase current in such a way that the active length of the inductor accounts for a fractional number of pairs of magnetic poles of the inductor 2p = 4/3, and the width of the phase zone of each coil group in magnetomotive force corresponds to or is less than 60 ° el.

8. The method according to p. 1, characterized in that they use an inductor with three coil groups per active length, connect the extreme coil groups to the midpoints of two pairs of power semiconductor switches of the inverter low-frequency power source, connect the central coil group to the midpoints of the other two pairs of power semiconductor keys of the inverter of the low-frequency power supply, set the current phase so that the active length of the inductor accounts for a fractional number of pairs of magnetic poles of the inductor 2p = 3/2, and the width the phase zone of each coil group in terms of magnetomotive force corresponded to 90 ° el.

9. The method according to p. 1, characterized in that the use of an inductor with three coil groups per active length, when installed on a furnace and connected to a three-phase or two-phase power source, and depending on the number of phases of the power source, choose a circuit for connecting the coil groups in this way either connect the coil groups to the midpoints of three pairs of power semiconductor switches of the inverter of the low-frequency power supply according to the “star” or “triangle” scheme and form magnetically moving forces of different phase and amplitude the neutral and lateral coil groups so that the width of the phase zone of each coil group in terms of magnetomotive force corresponds to either less than 60 ° e. two pairs of power switches of the inverter of the low-frequency power source, set the current phases so that the active length of the inductor accounts for a fractional number of pairs of magnetic poles of the inductor 2p = 3/2, and the width of the phase zone of each coil group in terms of magnetomotive force corresponded to 90 ° el. for which additional electric contacts are provided on the coil groups of the inductor to adjust the load for a particular switching circuit.

10. The method according to p. 1, characterized in that they create a combination of magnetic fluxes by forming on a multiphase winding a periodic voltage power source containing a spectrum from the main harmonic and additional harmonics of symmetric three-phase voltage systems of direct or reverse sequence.

11. The method according to p. 1, characterized in that it is carried out cyclically, the cycle includes one change in the direction of movement of the traveling magnetic field and in each cycle after changing the direction of movement of the traveling magnetic field, the frequency and magnitude of the voltage across the multiphase winding are changed.

12. The method according to p. 1 1, characterized in that the duration of exposure to a running magnetic field in one direction is 2-4 minutes

13. The method according to p. 1, characterized in that they use a low-frequency power source, including a rectifier based on UV-modules, when creating a longitudinal traveling and pulsating magnetic fields control the pulse sequence for each arm of the UV-module for the entire period, which are consistent with control inverter pulses based on SE modules.

14. The method according to p. 1, characterized in that they use a low-frequency power source, including an inverter based on SE modules, when creating a longitudinal traveling and pulsating magnetic fields, pulses with a PWM modulation frequency of less than 1000 Hz are controlled.

15. The electromagnetic stirrer for implementing the method according to claim 1, comprising an inductor and a low-frequency power source connected to it, the inductor comprising an open core with teeth and a multiphase winding of three coil groups located in grooves between the teeth of the core with coverage of the back of the core, characterized the fact that the number of turns of the extreme coil groups is greater than the number of turns of the central coil group, the central coil group is inverted relative to the extreme coil groups due to the direction windings or connections, and the coil groups are connected according to the “star” or “triangle” scheme and connected to the midpoints of three pairs of power switches of the inverter of the power source.

16. The mixer according to claim 15, characterized in that it contains at least two additional coil groups located on the core after the extreme coil groups relative to the middle of the core.

17. The mixer according to item 15, wherein the teeth of the core are made wider than the back of the core.

18. The mixer according to claim 15, characterized in that the core rod has a longitudinal cross-section variable in the longitudinal direction.

19. The mixer according to claim 15, characterized in that the back of the core is made of electrical steel and the teeth are made of structural steel.

20. The mixer according to claim 15, characterized in that the power supply on the DC bus contains a capacitance of more than 30 mF.

21. The mixer according to claim 15, characterized in that the inductor is connected to a low-frequency power supply by a shielded power cable with an even number of conductors, with half of the conductors connected to the beginning of the coil groups, and the other half of the conductors connected to the end of the coil groups.

22. The electromagnetic stirrer for implementing the method according to claim 1, comprising an inductor and a low-frequency power source connected to it, the inductor comprising an open core with teeth and a multiphase winding of at least three coil groups located in grooves between the teeth of the core with a back coverage core, characterized in that the extreme coil groups are connected sequentially and counterclockwise, while the number of turns of the extreme coil groups is less than or equal to the number of turns of the central coil groups, and in length not core even-numbered coil groups are inverted with respect to the odd-numbered coil groups due to the direction of the winding or the connection circuit.

23. The mixer according to claim 22, characterized in that it contains at least two additional coil groups located on the core after the extreme coil groups relative to the middle of the core.

24. The mixer according to item 22, wherein the teeth of the core are made wider than the back of the core.

25. The mixer according to item 22, wherein the inductor includes three coil groups, the inverter of the power source contains four pairs of power semiconductor switches, while the Central coil group is connected to the midpoints of the first two pairs of power semiconductor switches, and the extreme coil groups are connected to the second two pairs of power keys.

26. The mixer according to item 22, wherein the inductor includes four coil groups connected to the midpoints of the three pairs of power semiconductor switches of the inverter of the low-frequency power supply according to the "triangle", while the extreme coil groups are connected in one shoulder of the "triangle", the second longest core coil group is connected to the second shoulder of the “triangle”, and the third longest core coil group is connected to the third shoulder of the “triangle”.

27. The mixer according to item 22, wherein the inductor includes four coil groups connected to the midpoints of three pairs of power semiconductor switches of the inverter of the low-frequency power source in the "star" circuit, while the extreme coil groups are connected to the same phase of the "star", the second longest core coil group is connected to the second phase of the “star”, and the third longest core coil group is connected to the third phase of the “star”, and the zero point of the “star” is connected to the midpoint of two connected series tionary capacitors at the DC bus low frequency power source current.

28. The mixer according to claim 22, characterized in that the core rod has a transverse section that is variable in the longitudinal direction.

29. The mixer according to claim 22, characterized in that the cross section of the central part of the core core on which the central coil groups are located is larger than the cross section of the extreme parts of the core on which the extreme coil groups are located.

30. The stirrer according to item 22, wherein the back of the core is made of electrical steel, and the teeth are made of structural steel.

31. The mixer according to claim 22, wherein the power source comprises an active controllable rectifier based on power UVT modules.

32. The mixer according to item 22, wherein the power source on the DC bus contains a capacitance of more than 30 mF.

33. The mixer according to item 22, wherein the inductor is connected to a low-frequency power source by a shielded power cable with an even number of conductors, with half of the conductors connected to the beginning of the coil groups, and the other half of the conductors connected to the end of the coil groups.