JPS61159080A - Crucible type induction furnace - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a winding structure for a crucible induction furnace.

It is desirable that the crucible-type induction furnace be able to melt metal in a short time by inputting electric power as effectively as possible.

[Prior art and its problems]

As shown in Figure 2, a conventional crucible-type induction furnace is made up of a furnace body 1 made of a refractory material, around which a ζ coil 2 is wound.The coil 2 is generally a water-cooled coil insulated with a heat-resistant insulating material. When a metal (iron, aluminum, copper, etc.) is placed in the furnace and an alternating current is passed through the coil 2, an eddy current flows through the metal due to electromagnetic induction, and the metal is melted by the heat. As shown in Figure 2, when the furnace space is divided into the lower part and the upper part B, a cold lump of metal is first inserted into part A, and once the cold lump is melted, it is poured into the molten metal. Additional lumps are added, and the coil is energized until the molten metal fills part B. When the part B is completely filled with molten metal, the energization is stopped, the furnace body is tilted, and the molten metal is taken out. use,
It is designed so that some of the molten metal remains at the bottom, and a cold lump of metal is charged again to repeat the melting process. By the way, since this induction furnace has no iron core, the absorption power effective for melting is P.
.

When the voltage is E1, the current is E, and the power factor is E, P=EIa
Mφ, and this absorbed power is N turns -
It is approximately proportional to the magnetomotive force of the coil, that is, NI. Furthermore, the resistivity and magnetic permeability of the metal change when it is a cold lump and when it is in a molten state, and therefore the penetration depth of eddy currents differs. Since the penetration depth was greater in the molten state, the absorption power was also greater. In the melting process, there is a long period in which a cold lump of metal exists in part A, and in this state, the coil that contributes to melting is the part N in contact with part A.
Since there are only a times of absorption and the absorption power is small, it takes even more time. When the molten metal comes up to part B, the absorption power increases and it is filled with molten metal for a short time, but the molten metal is immediately taken out and used, so in the end, the excitation coil in contact with part B is useful for melting. It takes only a short amount of time, and the overall efficiency is poor and the dissolution process takes a long time.

As another conventional example to improve the above-mentioned drawbacks, as shown in Fig. 8, a middle tap is provided on the coil 2, and when there is no metal to be melted in the upper part, the tap is switched and the upper coil is disconnected. Although it is a large current tap changeover switch 81.8! The impedance will be too low if the lower coil is used alone, and excessive current will flow if the full voltage is applied, so the voltage must be adjusted in combination with a tapped transformer, and the current capacity of the lower coil must be changed. Since the absorption power cannot be increased,
Although it saves power, it does not improve melting efficiency and has the drawbacks of being expensive.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a crucible-type induction furnace which eliminates the above-mentioned drawbacks, has a simple structure, and improves melting efficiency.

[Key points of the invention]

The present invention divides the coil of a crucible-shaped induction furnace into two parts, upper and lower Cζ,
In an attempt to improve melting efficiency, the lower coil has fewer turns than the upper coil, has a larger current capacity, and is connected to an AC power source in parallel to heat the lower part of the furnace with more power than the upper part. It is something.

[Embodiments of the invention]

FIG. 1 shows an outline of the coil of the crucible-type induction furnace according to the embodiment of the present invention, in which the coil 2 wound around the furnace body 1 is divided into upper and lower halves, and the number of turns N1 of the lower coil is the number N1 of turns of the upper coil.
! The conductor cross section of the lower coil is made larger than that of the upper coil, and each fill is connected in parallel to the AC power supply. Assuming that the power supply voltage is E1, the power absorbed by the upper and lower coils is Pl, the current is 11, the power factor is rna4, the absorbed power of the upper coil is P''s current 12, and the power factor is αφ. Since Nl < Nl, the impedance of the N1 coil decreases and 11 increases.The conductor of the N1 coil is made thick to withstand IS.The rate of decrease in impedance is greater than the decrease in the number of turns of the coil. Therefore, the magnetomotive force it Nl)ig
It becomes N*. Therefore, the input power of the lower coil is greater than that of the upper part, and the melting efficiency of the lower part of the furnace increases, thereby increasing the melting efficiency of the furnace as a whole, thereby making it possible to shorten the melting time.

〔Effect of the invention〕

According to the present invention, by increasing the power input to the lower part of the furnace than to the upper part, the melting efficiency is improved, the melting process is shortened, and workability is improved.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a coil of a crucible-shaped induction furnace according to an embodiment of the present invention, Fig. 2 is a sectional view showing the schematic structure of a conventional crucible-shaped induction furnace, and Fig. 8 is a schematic diagram of a switched tapped coil. It is.

Claims (1)

[Claims] 1) The coil wound around the outer circumference of the furnace body is divided into two parts at the top and bottom of the furnace body, the lower coil has fewer turns than the upper coil, the conductor cross section is made larger, and each coil is connected in parallel to an AC power source. A crucible-shaped induction furnace characterized by: