JPH08261656A - Floating melting apparatus - Google Patents

Abstract

PURPOSE: To simplify the apparatus by eliminating a magnetic shielding plate between an upper exciting coil and a lower exciting coil. CONSTITUTION: Power is supplied from a voltage type inverter 50 to a serial resonance circuit having an upper exciting coil 1 and a capacitor 8, power is supplied from a current type inverter 60 to a parallel resonance circuit having a lower exciting coil 2 and a capacitor 9, and the output frequency of the inverter 50 is set to higher output frequency than that of the inverter 60. Thus, the capacitor 8 becomes higher impedance with respect to the output frequency of the inverter 60, the capacitor 9 becomes lower impedance with respect to the output frequency of the inverter 50, and hence a magnetic shielding plate can be eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention installs a copper crucible inside two sets of exciting coils, and puts an object to be heated such as metal into the copper crucible so that the object to be heated is levitated from the crucible. The present invention relates to a levitation melting device that melts in a levitation state.

[0002]

2. Description of the Related Art FIG. 3 shows a conventional example of a schematic configuration diagram of this type of levitation melting apparatus. In FIG. 3, 1 is an upper excitation coil, 2 is a lower excitation coil, 3 is a copper crucible, 4 is a material to be melted, 5 is a high frequency power supply for the upper excitation coil, 6 is a high frequency power supply for the lower excitation coil, and 7 is a magnetic shield plate. Is.

An eddy current flows through the copper crucible 3 and an eddy current flows through the melted material 4 due to the currents flowing through the upper excitation coil 1 and the lower excitation coil 2, respectively. The direction of the eddy current flowing in the copper crucible 3 and the material to be melted 4
Since the direction of the eddy current flowing in the opposite surface portions of the is opposite to that of the eddy current, a magnetic repulsive force is generated between the copper crucible 3 and the material 4 to be melted, and this repulsive force serves as a levitation force. The melting material 4 is levitated from the copper crucible 3. Further, the melted material 4 generates heat due to resistance loss and melts.

Here, in order that the material 4 to be melted does not come into contact with the copper crucible 3 and is located substantially at the center, it is necessary to increase the levitation force below the copper crucible 3. For this reason, the lower excitation coil 2 is supplied with electric power of a frequency lower than that of the upper excitation coil high frequency power supply 5 from the lower excitation coil high frequency power supply 6.

[0005]

In the above conventional levitation melting apparatus, the upper exciting coil 1 and the lower exciting coil 2 induce each other at different frequencies, and by this induction, the high frequency power source 5 for the upper exciting coil 5 and the lower portion. In order to prevent the high frequency power supplies 6 for exciting coils from malfunctioning, it is necessary to install a magnetic shield plate 7 between the upper exciting coil 1 and the lower exciting coil 2, and this magnetic shield plate 7 also has the above-mentioned structure. Since the eddy current flows to generate heat, it is necessary to provide a cooling device (not shown), which causes a problem that the structure of the levitation melting device becomes large and complicated.

Further, as described above, by making the frequency of the power source 5 for the upper excitation coil higher than the frequency of the power source 6 for the lower excitation coil, the voltage across the upper excitation coil 1 becomes high, and in particular, the levitation melting device When used in a vacuum, there was a risk of dielectric breakdown in the upper excitation coil 1. An object of the present invention is to provide a levitation melting apparatus that solves the above problems.

[0007]

In the first invention, an LC series circuit in which a first exciting coil and a first capacitor are connected in series, a second exciting coil and a second capacitor are provided. An LC parallel circuit connected in parallel, a first high frequency power supply for supplying power to the LC series circuit, and the LC
The parallel circuit is provided with a second high frequency power supply that supplies electric power having a frequency lower than that of the first high frequency power supply.

A second invention is the same as the first invention,
The first high frequency power source is a voltage type inverter, and the second high frequency power source is a current type inverter. Also, the third
In the invention, a first exciting coil having an intermediate tap, the intermediate tap being grounded, a first capacitor connected to one end of the exciting coil, and the other end of the exciting coil, A CLC series circuit including a first capacitor and a second capacitor having the same capacity, an LC parallel circuit in which a second exciting coil and a third capacitor are connected in parallel, and power is supplied to the CLC series circuit. A first high-frequency power supply and a second high-frequency power supply that supplies power to the LC parallel circuit at a frequency lower than that of the first high-frequency power supply.

A fourth invention is based on the third invention.
The first high frequency power source is a voltage type inverter, and the second high frequency power source is a current type inverter.

[0010]

In this type of levitation melting apparatus, in order to levitate and melt the material to be melted, the frequency of the first high frequency power source is set to 10 to 100 kHz and the second high frequency power source is set to the second frequency.
The frequency of the high frequency power source is set to 1 to 10 kHz. According to this invention, said LC series circuit or CLC
Each capacitor in the series circuit has a high impedance at the frequency of the second high frequency power supply, and has little influence on the first high frequency power supply. Similarly, the capacitors in the LC parallel circuit are the same as the first high frequency power supply. The common effect is that the frequency becomes low impedance and the influence on the second high frequency power source becomes small.

According to the second and fourth inventions, the L
C series circuit or CLC series circuit as a series resonance circuit,
If the frequency of the first high-frequency power supply is set near this resonance frequency, the power-supply voltage of the high-frequency power supply can be made the lowest, and since it is sufficient to supply substantially only effective power, the voltage source inverter is suitable. If the LC parallel circuit is a parallel resonance circuit, and the vicinity of this resonance frequency is the frequency of the second high frequency power supply, the power supply current of the high frequency power supply can be minimized, and it is sufficient to supply substantially only effective power. Is preferred.

Further, according to the third invention, an intermediate tap is provided on the first exciting coil having a high supply frequency, and the intermediate tap is connected to a ground point to increase the dielectric strength of the exciting coil. Let

[0013]

1 is a schematic configuration diagram of a flotation / melting apparatus showing a first embodiment of the present invention. Components having the same functions as those in FIG. The function different from that of FIG. 3 will be mainly described. That is, in FIG.
In the voltage type inverter 50 as the high frequency power source of the above, a three-phase AC power source is converted into a DC voltage by the diode bridge rectifier 51 and the smoothing capacitor 52, and this DC voltage is connected in reverse parallel with the diode and the semiconductor switching element. Is converted into a high frequency AC voltage by a single-phase bridge inverter 53 composed of, and high frequency power is supplied to the LC series circuit composed of the upper exciting coil 1 and the capacitor 8. The voltage type inverter 50 is a so-called series resonance type inverter in which the LC series circuit is used as a series resonance circuit and the single-phase bridge inverter 53 is operated in a switching operation in the vicinity of the resonance frequency.

Further, in the current source inverter 60 as the second high frequency power source, the three-phase AC power source is converted into a DC current by the thyristor bridge rectifier 61 and the smoothing reactor 62, and this DC current is converted into a thyristor bridge inverter 63.
Is converted into a high frequency alternating current, and high frequency power is supplied to the LC parallel circuit composed of the lower excitation coil 2 and the capacitor 9. The current source inverter 60 is a so-called parallel resonance type inverter in which the LC parallel circuit is used as a parallel resonance circuit to cause the thyristor bridge inverter 63 to perform a switching operation in the vicinity of the resonance frequency.

The capacitor 8 shown in FIG. 1 has the same function even if it is divided into both ends of the upper exciting coil 1, and a matching transformer is inserted between the voltage source inverter 50 and the LC series circuit. Also in the configuration, the function of the voltage source inverter 50 is the same. 2 is a schematic configuration diagram of a flotation / melting apparatus showing a second embodiment of the present invention. Components having the same functions as those in FIG. The function will be mainly described.

That is, in FIG. 2, the upper exciting coil 10 having the intermediate tap is grounded to the intermediate tap, and capacitors 11 and 1 are provided at both ends of the upper exciting coil 10, respectively.
2 is connected, and this CLC series circuit is used as a series resonance circuit, and the single-phase bridge inverter 53 of the voltage source inverter 50 is switched in the vicinity of this resonance frequency. The upper excitation coil 10 is formed by grounding the intermediate tap.
It is possible to double the withstand voltage of dielectric breakdown.

[0017]

According to the present invention, a magnetic shield plate is not required between the upper and lower two sets of exciting coils, so that the device can be downsized and the cost can be reduced. Further, in the upper excitation coil having the intermediate tap, the number of turns can be doubled and the output can be doubled with the same dielectric breakdown withstand capability.

Further, since two sets of high frequency power supplies can be realized by a voltage type inverter and a current type inverter respectively, the control characteristics are improved, and it is optimal for melting titanium, silicon, etc., for example.

[Brief description of drawings]

FIG. 1 is a block diagram of a flotation / melting apparatus showing a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a flotation / melting apparatus showing a second embodiment of the present invention.

FIG. 3 is a block diagram of a levitation melting apparatus showing a conventional example.

[Explanation of symbols]

 1 Upper Excitation Coil 2 Lower Excitation Coil 3 Copper Crucible 4 Dissolved Material 5 Upper Excitation Coil Power Supply 6 Lower Excitation Coil Power Supply 7 Magnetic Shield Plate 8 Capacitor 9 Capacitor 10 Upper Excitation Coil 11 Capacitor 12 Capacitor 50 Voltage Source Inverter 51 Diode Bridge Rectifier 52 Smoothing capacitor 53 Single-phase bridge inverter 60 Current source inverter 61 Thyristor bridge rectifier 62 Smoothing reactor 63 Thyristor bridge inverter

Front page continued (72) Inventor Mitsuru Fujita 1-1 Tanabe Shinden, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd. Within Fuji Electric Co., Ltd.

Claims (4)

[Claims] 1. An LC series circuit in which a first exciting coil and a first capacitor are connected in series, an LC parallel circuit in which a second exciting coil and a second capacitor are connected in parallel, and the LC series A levitation melting apparatus comprising: a first high frequency power supply for supplying electric power to a circuit; and a second high frequency power supply for supplying electric power of a frequency lower than that of the first high frequency power supply to the LC parallel circuit. . 2. The levitation melting apparatus according to claim 1, wherein the first high frequency power source is a voltage source inverter and the second high frequency power source is a current source inverter. 3. A first exciting coil having an intermediate tap, the intermediate tap being grounded, a first capacitor connected to one end of the exciting coil, and another end connected to the exciting coil, A CLC series circuit including a first capacitor and a second capacitor having the same capacity, an LC parallel circuit in which a second exciting coil and a third capacitor are connected in parallel, and power is supplied to the CLC series circuit. A levitation melting apparatus comprising: a first high-frequency power supply; and a second high-frequency power supply that supplies power to the LC parallel circuit at a frequency lower than that of the first high-frequency power supply. 4. The levitation melting apparatus according to claim 3, wherein the first high frequency power source is a voltage source inverter and the second high frequency power source is a current source inverter.