RU2433365C1 - Induction crucible furnace - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: furnace includes crucible, inductor with the main and additional coils, power supply, two capacitors one of which is in-series connected to the main coil and power supply, thus forming the main circuit, and the other one is connected to additional coils which are arranged around the main coil and are connected in series and opposite, thus forming short-circuited loop; at that, the number of turns of additional coils and capacity of capacitors are chosen so that the resonance condition can be met between inductively connected main and short-circuited loops.

EFFECT: invention allows effective mixing of molten metal and increases power factor of the plant.

3 dwg

Description

The invention relates to the field of metallurgy, in particular to induction crucible furnaces.

Known induction crucible furnace (AS No. 437900, IPC F27B 14/00, published 02.01.75), containing a crucible and a sectional inductor with increasing ampere turns to the upper end located above the melt zone.

Known induction crucible furnace (A.S. No. 954768, IPC F27D 11/06, published 08/30/82), containing a crucible, an inductor, the working part of which consists of a main single-phase coil and additional coils, powered by a current whose phase lags by 15- 90 electrical degrees from the phase of the current in the main coil.

The disadvantages of the known furnace include the fact that when it is used, high demands are placed on the power source, it has a low power factor Cosφ, and in general the installation has a low mixing intensity.

The basis of the invention is to increase the intensity of mixing of the metal in the furnace and power factor.

The problem is solved in that the induction crucible furnace containing the crucible, the inductor with the main and additional coils and a power source, according to the invention additionally contains two capacitors, one of which is connected in series with the main coil and the power source, forming the main circuit, and the other is connected to additional coils, which are placed around the main coil and connected in series and counterclockwise, forming a short-circuited circuit, while the number of turns of the additional coils and capacitively five capacitors are selected so as to satisfy the resonance condition is inductively coupled between ground and short-circuit path.

Figure 1 shows a sketch of an induction crucible furnace; figure 2 presents the electrical equivalent circuit of the induction crucible furnace; figure 3 is a vector diagram of currents and voltages.

(здесь и далее точкой обозначены комплексные величины), образуя основной контур.The induction crucible furnace contains a crucible 1, a main coil 2, around which there are two additional coils 3 ₁ , 3 ₂ connected in series and counterclockwise. The number of turns of the additional coils is not the same. The induction crucible furnace contains two capacitors 4 and 5. One of the capacitors 4 is connected to additional coils 3 ₁ , 3 ₂ so that it forms a short-circuited circuit. The main coil 2 with a capacitor 5 connected in series with it is connected to a single-phase AC voltage source

(hereinafter, the dot denotes complex quantities), forming the main contour.

Induction crucible furnace operates as follows.

в основной катушке возникает переменный электрический ток

который создает переменный магнитный поток

пронизывающий витки дополнительных катушек 3. Так как количество витков дополнительных катушек неодинаково, в последней возникает электрический ток

, создающий переменный магнитный поток

.When connecting the main circuit with the main coil 2 and capacitor 5 to a voltage source

an alternating electric current occurs in the main coil

which creates a variable magnetic flux

piercing turns of additional coils 3. Since the number of turns of additional coils is not the same, an electric current arises in the latter

creating a variable magnetic flux

.

и

имеют пространственный сдвиг, а в точках плоскости сечения между двумя дополнительными катушками l-l' (фиг.1) они перпендикулярны.Variable magnetic flux

and

have a spatial shift, and at the points of the plane of the section between the two additional coils ll '(Fig. 1) they are perpendicular.

и

образуют вращающееся магнитное поле, которое приводит расплавленный металл во вращательное движение по всей окружности тигля 1, причем вращающий момент имеет максимальное значение при условии, что величина фазового сдвига между переменными магнитными потоками

и

составляет 90°.Space-shifted magnetic fluxes

and

form a rotating magnetic field that causes the molten metal to rotate around the entire circumference of the crucible 1, and the torque has a maximum value provided that the magnitude of the phase shift between alternating magnetic fluxes

and

is 90 °.

To determine the relationship between the parameters of the elements of the electric circuit of the inventive furnace, allowing to obtain a phase shift of 90 °, we write the equations for two inductively coupled main and short-circuited circuits according to the law of Kirchhoff in a complex form (figure 2)

R ₁ , L ₁ , C ₁ - active resistance, inductance and capacitance of the main circuit;

R ₂ , L ₂ , C ₂ - active resistance, inductance and capacitance of the short-circuited circuit;

M ₁₂ = M ₂₁ - mutual inductance between the main and short-circuited circuits;

ω is the angular frequency of the supply voltage.

Knowing the magnitude of the inductances L _{1 of the} main coil 2 and L _{2 of the} additional coils 3, the capacitance of the capacitors 4 and 5 is chosen so that the condition

In this case, from equations (1) and (2) we have

When the condition ωМ ₁₂ = R _{2 is} fulfilled, expressions (4) and (5) are transformed to

.

.

Equations (1) and (2), subject to the above conditions, corresponds to the vector diagram of currents and voltages, presented in figure 3.

совпадает по фазе с напряжением сети

т.к. нагрузка (установка с индукционной тигельной печью) работает в режиме резонанса, т.е. потребляется из сети только активная мощность, и коэффициент мощности индукционной тигельной печи Cosφ=1.Current

coincides in phase with the mains voltage

because the load (installation with an induction crucible furnace) operates in resonance mode, i.e. only active power is consumed from the network, and the power factor of the induction crucible furnace is Cosφ = 1.

отстает по фазе от тока

на 90°, следовательно, такой же фазовый сдвиг относительно друг друга имеют переменные магнитные потоки

и

, что обеспечивает максимальный вращающий момент, а следовательно, и интенсивное перемешивание расплава металла.As follows from the vector diagram (figure 3), the current

lags in phase from current

90 °, therefore, the same phase shift relative to each other have variable magnetic fluxes

and

that provides maximum torque, and consequently, intensive mixing of the molten metal.

Claims (1)

An induction crucible furnace comprising a crucible, an inductor with a main and additional coils and a power source, characterized in that it further comprises two capacitors, one of which is connected in series with the main coil and the power source, forming a main circuit, and the other is connected to additional coils, which are placed around the main coil and connected in series and counterclockwise, forming a short-circuited circuit, while the number of turns of the additional coils and capacitance of the capacitors is chosen in such a way in order to satisfy the resonance condition between the inductively coupled main and squirrel-cage loops.

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