JPH06313684A - Arc furnace and induction heater - Google Patents

Abstract

PURPOSE:To eliminate influences of flicker and harmonic waves to a power network. CONSTITUTION:A generator 12 is driven by a prime mover 11. The generator 12 is so constituted as to obtain an output frequency of about 100-800Hz. An output of the generator 12 is supplied to an arc furnace 15 through a transformer 14 for the furnace. A melted material previously preheated by waste heat of the mover 11 is introduced to the furnace 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc furnace device and an induction heating device.

[0002]

2. Description of the Related Art Electric power is supplied to an arc furnace by a power supply system as shown in FIG. In FIG. 4, 66 to 15
The means for supplying the received voltage of 4 KV to the arc furnace R by stepping down with the receiving transformer T ₁ and the transformer T ₂ for the furnace is used. In FIG. 4, TCR is an electrode lift control device,
TUD is an electrode lifting device, CB is a furnace breaker, and DS is a disconnector. As described above, the power quality supplied to the arc furnace is 50HZ / 60HZ ± 1HZ. Further, the induction heating device used for manufacturing electric resistance welded pipes and the like has the same power quality as the above.

[0003]

The biggest problem in an arc furnace is that the relationship between the arc electrode and the molten scrap material is not constant, and the scrap material in the furnace melts down between the electrode and the material. Since the relative relationship collapses all at once, it has the property that the arc length fluctuates greatly, and large changes in load characteristics (maximum change short circuit) repeat at that time,
It happens frequently. As a result, a sharp voltage fluctuation (flicker) occurs, which has the effect of deteriorating the power quality from the consumer side to the power company side. In order to keep this quality within the allowable value, it is necessary to install a very expensive flicker prevention device (active filter).

Generally, the power conversion efficiency of a power company is about 35% overall. In order to supply power to an unspecified number of customers scattered throughout the country, a network is constructed using a power transmission and distribution network, and monitoring, control, and
Protects. Not only for the purpose of integrating the power of heat, but also for the users whose frequency value is important, the electric power company controls the quality so that it does not change more than 1HZ (instantaneous speed). .

However, for the purpose of obtaining heat from the equipment, the quality of the electric power does not become a problem so much, so that the wasteful depreciation of the equipment is paid. Also, due to the large fluctuations in the load characteristics, there is a need to constantly be careful not to exceed the contracted electric energy (demand) with the electric power company.

The above is the case of the arc furnace, but in the case of the induction heating device, since the heating characteristics cannot be obtained with the purchased power of 50 HZ or 60 HZ, the frequency is converted and used. In order to convert the frequency, a means of once converting the alternating current of 50HZ or 60HZ into the direct current and then converting it back to the desired frequency is adopted. In order to control the output together, rectification is usually performed using phase control with a thyristor,
You are getting DC output. However, the phase control of the thyristor exerts a distorted voltage containing harmonics of each order on the power grid. In order to keep this within an allowable value, it is necessary to install a very expensive harmonic wave suppression device (active filter or LC filter). Besides, there are the same problems as in the arc furnace. As described above, the arc furnace and the induction heating device have the above-mentioned problems.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an arc furnace apparatus and an induction heating apparatus in which the influence of flicker and harmonics on the electric power network is prevented.

[0008]

In order to achieve the above object, the present invention is directed to a first aspect of the present invention, a prime mover, a generator that is driven by the prime mover, and outputs an output having a frequency of 100HZ to 800HZ, and this power generation. The output of the machine is supplied to the primary side,
A transformer for outputting the arc furnace supply voltage to the secondary side and a preheating furnace for supplying the exhaust heat of the prime mover to preheat the material melted in the arc furnace are provided.

A second aspect of the present invention is directed to a prime mover, a generator driven by the prime mover and delivering an output having a frequency of 100HZ to 800HZ, and an output end of the generator is connected to a primary side.
A matching transformer having an induction heating coil connected to the secondary side thereof, a capacitor connected to the secondary side of the matching transformer, and a preheating furnace to which the exhaust heat of the prime mover is supplied to preheat a material to be heated Is.

According to a third aspect of the invention, the AC output of the generator is input,
A forward converter that obtains a DC output is provided, and an inverse converter that receives the DC output of the forward converter and that provides an induction heating coil with an output of a frequency higher than the output frequency of the generator is provided.

[0011]

Operation: The output frequency of the generator driven by the prime mover is set to 10
Since it is set to 0HZ to 800HZ, the heating characteristics by the arc furnace or induction heating can be improved. Also, in advance,
Since the melted material and the material to be heated are preheated by using the exhaust heat of the prime mover, it is possible to improve the utilization efficiency of the heat generation energy.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a first embodiment, and in FIG. 1, 11 is a prime mover composed of a marine engine or the like, and a generator 12 is connected to the prime mover 11. The output of this generator 12 is 5 MW
.About.100 MW and an output frequency of 100 HZ to 800 HZ are used. For example, using a generator with an output frequency of 300 HZ ± 15 HZ has the advantage that the weight of the iron core is about 1/6 of 50 HZ. The output end of the generator 12 is connected to the primary side of the arc furnace transformer 14 using an aluminum bus 13. An arc furnace 15 is connected to the secondary side of the arc furnace transformer 14 using a flexible cable 16. Reference numeral 17 denotes a preheating furnace for preheating the molten material, and the heat discharged from the prime mover 11 is supplied to the preheating furnace 17. The exhaust heat temperature from the prime mover 11 is about 400 ° C. at high temperature. By preheating the melted material at this temperature before being put into the arc furnace 15, the conversion efficiency in the arc furnace 15 becomes good. A circuit 18 controls the field of the generator 12. 19 is a vacuum breaker.

In the first embodiment constructed as described above, the molten material is preheated in the preheating furnace 17 before the molten material is charged into the arc furnace 15. The molten material that has been preheated is the arc furnace 1
It is thrown in 5. The arc furnace 15 melts the melting material with the output from the generator 12. The arc current control in the arc furnace 15 is performed by the field control circuit 18.

With the construction as in the first embodiment, the following effects can be obtained.

(A) The exothermic energy of fossil fuel can be used 90% or more (including the reuse of exhaust heat).

(B) High level energy (arc) that cannot be obtained by combustion energy (temperature, energy density) can be used in the form of electric energy.

(C) Flicker does not affect the electric power network of the electric power company.

(D) A large-capacity marine engine can be used. As a result, heat costs can be lower than electricity purchase.

(E) The flywheel can be eliminated or minimized without the frequency variation control of ± 1 HZ.

(F) It is not necessary to allocate a management device or an operator to the power demand so that the demand value of the contract condition with the power company is not exceeded.

(G) When the load is short-circuited, the demagnetization characteristics act on the generator, resulting in a decrease in output and at the same time, the frequency (100 Hz-
800 HZ), the current value itself also decreases due to the increase in short-circuit impedance, and the current rising characteristic (di
/ Dt) is significantly reduced, and current limiting control is possible without short-circuit interruption. As a result, the operating rate can be improved.

(H) No on-road tap change is required.

(I) The total cost versus performance can be greatly improved.

FIG. 2A shows a second embodiment of the present invention. The same parts as those of the first embodiment of FIG. 1 are designated by the same reference numerals. In FIG. 2A, 20 is the output current I of the generator 12.
The voltage V detection unit supplies the current I and voltage V detected by the detection unit 20 to the field control circuit 18. The field control circuit 18 uses the current I and the voltage V to generate the power from the generator 12.
Field is controlled and its output is controlled. 21a, 2
1b and 21c are matching transformers, and these transformers 21a and 21c
The primary side of b, 21c is connected to the output end of the generator 12,
The secondary side is connected to induction heating coils 23a, 23b, 23c for heating the work 22 which is the material to be heated. Two
4a, 24b, 24c are power factor adjusting capacitors, 25a,
Reference numerals 25b and 25c denote rolls that convey the work 22 preheated in the preheating furnace 17.

In the second embodiment configured as described above, the work 22 is preheated in the preheating furnace 17 in advance (heated to be higher than room temperature indicated by the broken line as in the time-temperature characteristic shown in FIG. 2B). , Induction heating coils 23a, 23b, 2
3c to carry. Induction heating coils 23a, 23b, 2
Since the frequency of, for example, 300 HZ output from the generator 12 is supplied to 3c, the work 22 is gradually heated from the left side to the right side in the drawing, and its temperature rises. FIG. 2B shows the progress of the temperature rise.
Is. As shown in FIG. 2B, the work 22 is heated to about 950 ° C. by the induction heating coil 23c. In addition,
The field control of the generator 12 controls the entire second embodiment.

FIG. 3A shows a third embodiment, which is shown in FIG.
The same parts as those of the first and second embodiments of FIG. 2 are designated by the same reference numerals. In FIG. 3A, 31 is an inverter transformer with a frequency of 300 HZ, the primary side of this inverter transformer 31 is connected to the output end of the generator 12, and the secondary side is connected to the forward converter 32. The output converted into the direct current by the forward converter 32 is again converted into the alternating current by the reverse converters 33a, 33b, and 33c, but at this time, the output frequency is about 5 times that of the generator 12 (about 1500 HZ). To be converted. The outputs of the inverse converters 33a, 33b, 33c are the induction heating coil 2
3a, 23b, 23c, and the work 22 is fed to the work 22 shown in FIG.
The temperature is raised to the temperature distribution shown in. Since the work 22 is heated at a high frequency (1500 HZ) as in the third embodiment, the heating characteristic becomes good. Further, the entire control is performed by the field control of the generator as in the second embodiment.

With the configuration as in the second and third embodiments, the following effects can be obtained in addition to the effects of the first embodiment.

(B) Harmonic effects are not given to the power network.

(B) It is possible to construct with its own lead time without being influenced by the transmission network expansion schedule of the electric power company, and the timing of capital investment is not lost.

(C) By increasing the number of poles of the generator and increasing the output frequency, it is possible to reduce the amount of iron core, reduce the shape of the generator, and reduce the manufacturing cost.

[0031]

As described above, according to the present invention,
There are advantages that the heat generation energy of fossil fuels can be effectively used, that the power grid is not adversely affected by flicker and harmonics, and that frequency fluctuations do not have to be controlled. In addition, there is an advantage that it is not necessary to manage the power demand so as not to exceed the demand value of the contract conditions with the power company.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of the present invention.

FIG. 2A is a schematic configuration diagram showing a second embodiment, and B is a temperature distribution characteristic diagram.

FIG. 3A is a schematic configuration diagram showing a third embodiment, and B is a temperature distribution characteristic diagram.

FIG. 4 is an explanatory diagram showing a conventional arc furnace power supply system.

[Explanation of symbols]

 11 ... motor 12 ... generator 14 ... arc furnace transformer 15 ... arc furnace 17 ... preheating furnace

Claims (3)

[Claims] 1. A prime mover, a generator driven by this prime mover and delivering an output of a frequency of 100 HZ to 800 HZ, the output of this generator is supplied to a primary side, and an arc furnace supply voltage is supplied to a secondary side. An arc furnace apparatus comprising: a transformer for outputting; and a preheating furnace which is supplied with exhaust heat of the prime mover and preheats a material melted in the arc furnace. 2. A prime mover, a generator driven by this prime mover and delivering an output having a frequency of 100 HZ to 800 HZ, an output end of this generator is connected to the primary side, and an induction heating coil is provided on the secondary side. An induction heating apparatus comprising: a matching transformer connected thereto; a condenser connected to a secondary side of the matching transformer; and a preheating furnace for preheating a material to be heated to which exhaust heat of the prime mover is supplied. . 3. A forward converter for receiving an AC output of a generator and obtaining a DC output as an output, and a DC output of this forward converter for inputting an induction heating coil with a frequency higher than the output frequency of the generator. The inverse heating device according to claim 2, further comprising: