JPS6347237B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a melting operation command device for an induction furnace. In general, it is necessary to operate an induction furnace to maximize the input load factor to improve the actual melting capacity while saving labor and increasing the amount of hot water discharged, that is, the production amount. BACKGROUND ART Conventionally, a power supply device such as a thyristor inverter device, which limits voltage and current, which is installed in an induction furnace, has an output characteristic as shown in FIG. In other words, if the horizontal axis represents the output current and the vertical axis represents the output voltage, the line segment AM extending upward from point A on the horizontal axis and parallel to the vertical axis indicates the output current limit value and the output voltage limit. A line segment extending to the right and parallel to the horizontal axis from point D on the vertical axis that indicates the value
The point M where DM intersects is the maximum output point. Furthermore, Fig. 1 shows that the load impedance of the power supply changes depending on the amount of melted material input into the furnace and the melting state of the melted material in the furnace, and therefore the output of the power supply, output voltage, and It shows how the output current changes within each limit value. That is, the origin O
The curve represented by the line segment OM from to point M is the load characteristic when the load factor of the power supply is 100%,
The curve represented by the line segment OC shows load characteristics when the input amount of melted material is too small, the output current is low, and the load factor of the power supply is low.
The curve represented by OB shows a load characteristic in which the output voltage is low when the input amount of melted material is too large, and the load factor of the power supply device is low. In addition, the curve ○A represented by the line segment OE is a case where the melting material in the furnace during melting work is not completely melted, and the output voltage is low and the load factor is low. In this case, when the amount of melted material input is too small, the output current may be small and the load factor may exhibit characteristics that are low. Furthermore, curve ○ and b, represented by the line segment OF, indicate that the melted material in the furnace during melting work is completely melted, that is, melted through, but when the amount of molten metal is approximately 25% of the rated value of the furnace. , the load factor is low, and the curve ○C represented by the line segment OG shows that the molten material has melted through, but when the amount of molten metal is about 50% of the furnace's rated value, the load factor is low. It shows low characteristics. Including line segment OM and line segment OI
The shaded area ○D surrounded by OJ indicates that the molten material in the furnace has melted down, and the amount of molten metal is almost equal to the rated value of the furnace, and the load factor is almost 100%.
It is. Further, the curve ○ho represented by the line segment OH shows the load characteristics when there is a shortage of melted material, and the M' point shows the operating point during heat retention operation at the rated molten metal amount when melting is completed. Further, point K is an operating point when the current setting value is I _o and the voltage setting value is V _o . Conventionally, under the various operating conditions of the induction furnace that produce the load characteristics described above, the method used was to introduce molten material into the furnace at an arbitrary time based on the intuition of the operator through visual inspection of the inside of the furnace. Therefore, the amount of melted material input may be too much or too little, leading to operational problems such as a drop in the load rate as mentioned above.At the same time, it is necessary to constantly monitor the melting state, so a full-time worker is assigned. However, there was a problem in terms of operating costs. The present invention has been made in view of the above problems, and its purpose is to detect changes in the voltage, current, and load impedance of the power supply device of an induction furnace, compare each with set values, and use the results as a basis. Therefore, the melting work command for the induction furnace can improve the actual melting capacity and save labor by increasing the load ratio of the power supply device by sequentially outputting appropriate work commands to maintain the load factor at the maximum. The purpose is to provide equipment. Hereinafter, one embodiment of the present invention will be described based on the drawings. As shown in FIG. 2, 1 is a power supply device, and this power supply device 1 is composed of, for example, a thyristor inverter, and has a voltage limit and a current limit as shown in FIG. The input terminal 1a of this power supply device 1 and the power supply point 2 are connected by an electric line 3, and further,
An output terminal 1b of the power supply device 1 is connected to capacitors 5 and 6 constituting the induction furnace 4 and a coil 8 provided in the furnace body 7 through an electric line 9. A current transformer 10 for detecting the input current of the power supply device 1 is provided in the above-mentioned electric line 3, and this current transformer 10
An output terminal 10a of the detector is connected to an input terminal 11a of the detection input regulator 11. Further, a transformer 15 for detecting the output voltage of the power supply device 1 is connected to the above-mentioned electric line 9.
The primary side terminal of this transformer 15 is connected, and the secondary side terminal of this transformer 15 is connected to the input terminal 11b of the detection input regulator 11. In the detection input regulator 11, a signal V ₀ representing the output voltage of the power supply device 1, a signal I ₀ representing the input current of the power supply device 1, and a value obtained by dividing the above signal V ₀ by the signal I ₀ , that is, A signal V ₀ /I ₀ representing the impedance of the induction furnace 4 is output from the output terminals 11c and 11.
d and 11e, respectively. Output terminals 11c, 11d, and 11e of this detection input regulator 11 are connected to input terminals 12a, 12b, and 12c of a comparator 12, respectively. In the comparator 12, the load factor is approximately
The voltage V _o , current I _o , and impedance V _o /I _o for operation at 100% are set in advance, and the set value V _o of the output voltage of this power supply 1 and the actual output voltage
A comparison of the magnitude with V ₀ , a comparison of the magnitude of the set value I _o of the input current of the power supply 1 with the actual input current I ₀ , and a value obtained by dividing the above set value V _o by the set value I _o , that is, the induction furnace The set value V _o /I _o of the impedance of the induction furnace 4 is compared in magnitude with the signal V _o /I _o which is the actual value of the impedance of the induction furnace 4, and then the comparator 12
, signals corresponding to the results of the above-mentioned comparison calculations are outputted to output terminals 12d to 12j, respectively. When the actual voltage value V ₀ is greater than the set voltage value V _o , a signal is output to terminal 12d, and the actual voltage value
When V ₀ is smaller than the voltage set value V _o , a signal is output to the terminal 12e, and when the actual current value I ₀ is greater than the current set value I _o , a signal is output to the terminal 12f, Actual value I ₀ is current set value I _o
When the actual value of impedance V ₀ /I ₀ is larger than the set value of impedance V _o /I _o , a signal is output to terminal 12g.
A signal is output at 2h, and the actual value of impedance is
When V ₀ /I ₀ is smaller than the set value V _o /I _o , a signal is output to terminal 12i, and when the actual impedance value V ₀ /I ₀ is almost equal to the set impedance value V _o /I _o A signal is output to the terminal 12j. Output terminal 12d, 1 of this comparator 12
2e, 12f, 12g, 12h, 12i, 12j
are the input terminals 13a, 13 of the work command control device 13
b, 13c, 13d, 13e, 13f, and 13g, respectively. The work command control device 13 determines the operating state of the induction furnace 4 according to the signal input from the comparator 12, issues a predetermined work command according to this result, and transmits this signal to the work command display device. 14. The work command control device 13 calculates the actual value of the input current of the power supply device 1 as shown in Table 1.
As I ₀ becomes smaller than the set value I _o , the actual value of the impedance of the induction furnace 4 seen from the power supply 1 V ₀ /I ₀
When becomes larger than the set value V _o /I _o , a signal indicating that the amount of melted material input is insufficient is output to the terminal 13h, and the actual value V ₀ of the output voltage of the power supply device 1 is larger than the set value V _o When the actual value of the input current _I0 becomes smaller than the set value _Io , a signal representing the burn-through of the melted material is output to the terminal 13i, and the actual value of the voltage _V0 becomes larger than the set value _V0. When the actual value of the current I ₀ becomes smaller than the set value I _o and the actual value of impedance V ₀ /I ₀ becomes larger than the set value V _o /I _o , the preparation for charging the melted material is completed. A signal representing

[Table] When the actual voltage value V ₀ becomes larger than the set value V _o , the actual current value I ₀ becomes smaller than the set value I _o , and the actual impedance value V ₀ /I ₀ becomes the set value.
When it becomes smaller than V _o /I _o , a signal representing a command to input melted material is output to terminal 13k, and the actual value of the voltage is output.
When V ₀ becomes smaller than the set value V _o and the actual value of the current I ₀ becomes smaller than the set value I _o and the actual value of impedance V ₀ /I ₀ becomes larger than the set value V _o /I _o ,
A signal representing the completion of feeding, which is a command to stop feeding the melted material, is output to the terminal 13l, and the actual voltage value V ₀ becomes smaller than the set value V _o and the actual current value I ₀ becomes larger than the set value I _o . And when the actual value of impedance V ₀ /I ₀ and the set value V _o /I _o are almost equal,
A signal representing the burn-through of the rated amount of melted material is output to terminal 13m, and furthermore, the actual value of voltage V ₀ becomes smaller than the set value V _o and the actual value of current I ₀ becomes larger than the set value I _o and the actual value of impedance
When the set time of timer a provided in this work command control device 13 has elapsed since V ₀ /I ₀ and the set value V _o /I _o became almost equal, a signal indicating completion of adding the rated amount of melted material is generated. is output to terminal 13n, and the actual voltage value V ₀ becomes smaller than the set value V _o , the actual current value I ₀ becomes larger than the set value I _o , and the actual value of impedance is set to V ₀ /I ₀ . When the set time of timer a has elapsed since the value V _o /I _o became almost equal, a signal representing a command to adjust the composition of the molten metal is output to terminal 13 o, and the actual voltage value V ₀ becomes the set value.
As V _o becomes smaller, the actual value of current I ₀ becomes the set value
I _o and the actual value of impedance V ₀ /
When I ₀ and set value V _o /I _o become almost equal, timer a
When the set time of timer b provided in the work command control device 13 has elapsed, a signal representing a command to measure the temperature of the molten metal is output to the terminal 13p, and the actual voltage value V ₀ is When the actual value of current I ₀ becomes smaller than the set value V _o and becomes larger than the set value I _o and the actual value of impedance V ₀ /I ₀ and the set value V _o /I _o become almost equal, timer a is activated. After the set time and the set time of timer b have elapsed, a timer c provided in the work command control device 13 is activated.
When the set time has elapsed, a signal indicating the completion of melting is output to the terminal 13q, and the actual voltage value V ₀ becomes smaller than the set value V _o and the actual current value I ₀ becomes larger than the set value I _o . And the actual value of impedance
When V ₀ /I ₀ and the set value V _o /I _o become almost equal, the set time of timer a, the set time of timer b, and the set time of timer c
When the set time and the set time of the timer d provided in the work command control device 13 have elapsed, a signal representing the hot water tapping command is output to the terminal 13r, and the actual value of the voltage is output.
As V ₀ becomes smaller than the set value V _o , the actual value of current I ₀ becomes smaller than the set value I _o , and the actual value of impedance V ₀ /I ₀ and the set value V _o /I _o become almost equal. When a signal representing a warming operation command is sent to terminal 13s,
Output to. Output terminal 13 of the above-mentioned work command control device 13
h, 13i, 13j, 13k, 13l, 13m,
13n, 13o, 13p, 13q, 13r, 13
s is the "insufficient amount of melted material input" indicator 14a of the work command display device 14, and "melted material melted through"
Display 14b, "Preparation for charging melting material" display 1
4c, "Insertion of melted material" indicator 14d, "Insertion of melted material completed" indicator 14e, "Rated amount of melted material melted through" indicator 14f, "Completion of addition of rated amount of melted material" indicator 14g, " ``Molten metal composition adjustment'' display 14h, ``molten metal temperature measurement'' display 14i, ``melt completion'' display 14j, ``molten metal release'' display 14k,
They are each connected to the "warming operation" display 14l. Next, the operation of the above-mentioned melting work command device will be explained. When the induction furnace 4 is operated, the output voltage of the power supply device 1 is inputted to the detection input regulator 11 via the transformer 15, and the input current of the power supply device 1 is detected by the current transformer 10. The output signal of this current transformer 10 is input to a detection input regulator 11. In the detection input regulator 11, the output signal of the transformer 15 is converted into a signal representing the output voltage V ₀ of the power supply device 1 and outputted, and the output signal of the current transformer 10 is converted into a signal representing the input current I ₀ of the power supply device 1. The impedance V ₀ /I ₀ of the induction furnace 4 viewed from the power supply device 1 at this time is calculated,
A signal representing this impedance V ₀ /I ₀ is output. Actual values of voltage, current and impedance output from the above-mentioned detection input regulator 11 V ₀ , I ₀ ,
V ₀ /I ₀ is input to the comparator 12 and compared with set values V _o , I _o , and V _o /I _o of voltage, current, and impedance, respectively. If the amount of melted material input into the induction furnace does not reach the rated amount after the operation of the induction furnace 4 is started, for example, the load characteristic is the curve ○ho in Fig. 1, and the actual value of the current I ₀ is smaller than the set value I _o , and a signal is output to the terminal 12g of the comparator 12. At the same time, the actual impedance value V ₀ /I ₀ is larger than the set value V _o /I _o , and the signal is output to the terminal 12h of the comparator 12. A signal is output to this terminal 12g, 12
The signal h is input to the work command control device 13.
Here, the work command control device 13 outputs a signal indicating an insufficient amount of melted material input to the terminal 13h, and inputs the signal from the terminal 13h to the "insufficient amount of melted material input" indicator 14a of the work command display device 14. However, a message indicating that the amount of melted material input is insufficient is displayed. Next, when the molten material that does not reach the rated amount input melts down, for example, curve ○○ in Figure 1,
○C is the load characteristic, and the actual voltage value V ₀ is the set value
is greater than V _o and terminal 12 of comparator 12
A signal is output to the terminal 12g of the comparator 12, and a signal is output to the terminal 12g of the comparator 12 because the actual value _I0 of the current is smaller than the set value _Io .
The signal g is input to the work command control device 13.
Here, the work command control device 13 outputs a signal representing melted material burn-through to the terminal 13i, inputs the signal of this terminal 13i to the "melted material burn-through" display 14b of the work command display device 14, The burn-through of the melted material is displayed. Furthermore, in this state, the actual value of impedance V ₀ /I ₀ is the set value
If it is larger than V _o /I _o , a signal is output to the terminal 12h of the comparator 12, and the signal at this terminal 12h is input to the work command control device 13. here,
The work command control device 13 outputs a signal to the terminal 13j indicating that it is possible to input the melted material, and inputs the signal from the terminal 13j to the "preparation for charging the melted material" indicator 14c of the work command display device 14. A display indicating preparation for inputting the melting material is displayed. This display of preparation for charging continues until the rated amount is completed. Further, when the actual impedance value V ₀ /I ₀ becomes smaller than the set value V _o /I _o after the melted material has melted through, a signal is output to the terminal 12i of the comparator 12, and the signal at this terminal 12i The command is input to the command control device 13. Here, the work command control device 13 sends a signal representing a melt material input command to the terminal 1.
3k, and the signal from this terminal 13k is sent to the "adding melted material" indicator 14d of the work command display device 14.
is input, and a command to input the melted material is displayed. When the actual voltage value V ₀ becomes smaller than the set value V _o due to the introduction of melted material into the induction furnace, a signal is output to the terminal 12e of the comparator 12, and the actual impedance value V ₀ /I ₀ is the set value
becomes larger than V _o /I _o , and terminal 1 of comparator 12
A signal is output at 2h, and at this time, the actual value _I0 of the current is smaller than the set value _Io , and a signal is output to the terminal 12g of the comparator 12.
Signals e, 12g, and 12h are sent to the work command control device 1.
3 is input. Here, the work command control device 13
outputs a charging completion signal, which is a command to stop charging the melted material, to the terminal 13l, and inputs the signal from the terminal 13l to the "melted material charging complete" indicator 14e of the work command display device 14, indicating that the charging of the melted material is complete. is displayed. Next, when the rated amount of melted material charged into the induction furnace melts down, the actual value of voltage V ₀ is less than the set value V _o and the actual value of current I ₀ is greater than the set value I _o As well as the actual value of impedance
V ₀ /I ₀ becomes almost equal to the set value V _o /I _o , and signals are output to terminals 12e, 12f, 12j of the comparator 12, respectively.
The signal j is input to the work command control device 13.
Here, the work command control device 13 sends a signal to the terminal 13 indicating that the rated amount of the melted material has melted through.
The signal of this terminal 13m is inputted to the "nominal amount of melted material burn-through" display 14f of the work command display device 14, and the rated amount of melted material burn-through is displayed. Furthermore, when the set time of timer a provided in the work command control device 13 has elapsed from this state, a signal indicating completion of inputting the rated amount of melted material is output to the terminal 13n of the work command control device 13, and this terminal 13n This signal is input to the "completion of adding the rated amount of melted material" indicator 14g of the work command display device 14, and the completion of adding the rated amount of melted material is displayed. Also, at this time, a signal representing a command to adjust the composition of the molten metal is output to the terminal 13o of the work command control device 13, and this signal from the terminal 13o is input to the “adjustment of molten metal composition” display 14h of the work command display device 14. The command for adjusting the composition of the molten metal is displayed. When the set time of timer b has elapsed after the set time of timer a has elapsed, a signal representing a command to measure the temperature of the molten metal is output to the terminal 13p of the work command control device 13, and this signal at the terminal 13p is used as the work command. “Molten metal temperature measurement” display device 1 of display device 14
4i, and a molten metal temperature measurement command is displayed. Furthermore, when the set time of timer c elapses after the set time of timer b has elapsed, a signal indicating the completion of melting is output to the terminal 13q of the work command control device 13, and this signal is sent to the work command display device 1.
4 is input to the "dissolution complete" display 14j, and a display indicating the completion of dissolution is performed. Further, when the set time of timer d has elapsed after the set time of timer c has elapsed, a signal representing a hot water tapping command is output to the terminal 13r of the work command control device 13, and the signal of this terminal 13r is transmitted to the work command display device 14. “Hot water” indicator 1
4k, and the hot water is displayed. In addition, when the rated amount of molten metal is kept warm after melting is completed, the actual voltage value V ₀ is smaller than the set value, and the actual current value I ₀ is also smaller than the set value I _o . At the same time, the actual impedance value V ₀ /I ₀ becomes almost equal to the set value V _o /I _o , and a signal representing a warming operation command is output to the terminal 13s of the work command control device 13. “Keep warm operation” indicator 1 of command display device 14
4l is input, and the heat retention operation is displayed. As explained above, in the present invention, the actual values of the voltage and current of the power supply device that supplies power to the induction furnace, the actual value of the load impedance calculated from the actual values of the voltage and current, and the load factor of the power supply device are set to the maximum value. It is equipped with a comparison means for comparing the set values of voltage, current, and load impedance, respectively, and a work command means for issuing a command for a predetermined work item according to the result of this comparison. is carried out based on the commands of the work command means, and the induction furnace is operated so that the load factor of the power supply device is maximized. Therefore, it is possible to improve the actual melting capacity, that is, increase the amount of hot water dispensed. Further, since there is no need to constantly monitor the operating state of the induction furnace, labor savings can be achieved.

[Brief explanation of drawings]

FIG. 1 is a graph showing the load characteristics of a power supply device for an induction furnace, and FIG. 2 is a block diagram showing an embodiment of the present invention. 1...Power supply device, 4...Induction furnace, 10...Current transformer, 1
1...Detection input adjuster, 12...Comparator, 13
...Work command control device, 15...Transformer.

Claims (1)

[Claims] 1. means for detecting the actual value of the voltage of the power supply device for supplying power to the induction furnace; means for detecting the actual value of the current of the power supply device; a calculation means for calculating the actual value of the load impedance; An induction furnace characterized by comprising a comparison means for comparing each and outputting a signal according to the result of the comparison, and a work command means for commanding a predetermined work item in response to the output signal of the comparison means. Melting work command device.