JPH0331035Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a device for controlling the vertical positioning of an arc furnace electrode in a steelmaking arc furnace, etc., and particularly to a device configuration for improving the operational efficiency of the arc furnace.

[Prior art and its problems]

For example, in a steelmaking arc furnace, after steel scrap, which is the main raw material, is charged into the furnace, three carbon cylindrical electrodes are inserted into the furnace from above, and a commercial frequency three-phase AC voltage is applied to the electrodes. is applied to generate an arc between each electrode and the scrap, and the scrap is melted by the arc heat.In such an arc furnace, the electrodes are normally It is customary to control the impedance between the metal and the heated object such as scrap to a constant value, and this constant impedance control usually changes the arc current depending on the arc voltage, that is, the electrode current, by adjusting the arc length. This is done under control by adjusting the Therefore, such an arc furnace is provided with an electrode drive mechanism that drives the electrode in the vertical direction to adjust the arc length, and this electrode drive mechanism drives the electrode according to the voltage applied to the electrode. An electrode control device including the electrode drive mechanism is provided, which uses a current determined by a predetermined impedance as a reference value and drives the electrode so that the actual electrode current is equal to this reference value.

Since the electrode control device is constructed as described above, the scrap is melted by the arc, and as a result, as the surface of the scrap facing the electrode tip gradually descends, the arc length tends to become longer, so that it follows the surface. The electrode also lowers. However, if the electrode falls excessively due to a failure of the electrode drive mechanism, the bottom of the furnace will collide with the electrode, resulting in damage to the bottom of the furnace or breakage of the electrode. Usually, the electrode controller is equipped with a sensor that detects the lower limit position of the electrode.
When the electrode descends and reaches the lower limit position, the electrode drive mechanism is normally provided with a signal cutting mechanism that stops the electrode by preventing the drive signal from being input to the electrode drive mechanism by the sensor. When this signal cutoff mechanism operates, the electrode is moved above the lower limit position by a manual operation mechanism provided separately from the above-mentioned parts to continue the heating operation. As a result, in conventional electrode control devices, when the electrode reaches the lower limit position and the signal cutoff mechanism is operating, unmelted scrap may fall from around the electrode, or scraps other than the electrode may fall. Even if it becomes necessary to raise the electrode because the arc length shortens or the arc current increases because the electrode is lowered,
Since the electrode does not rise automatically because the above-mentioned shrinking mechanism is working, there is a problem in that in such cases it is necessary to manually pull up the electrode each time to continue automatic heating. However, the conventional electrode control device has a problem in that it is difficult to improve the operational efficiency of the arc furnace.

[Purpose of invention]

The present invention solves the problems with the conventional electrode control device for arc furnaces as described above, and when the electrode current increases more than the reference value with the electrode reaching the lower limit position, manual operation as described above is required. It is an object of the present invention to provide an electrode control device for an arc furnace that can automatically pull up the electrode and continue arc heating without causing any damage, thereby improving the operating efficiency of the arc furnace.

[Key points of the idea]

In order to achieve this purpose, the present invention
a deviation calculation unit that outputs a deviation signal between a current command value signal calculated from a voltage signal corresponding to the applied voltage of the arc furnace electrode and a predetermined impedance, and a current actual value signal corresponding to the energization current of the electrode; an adjustment unit to which a set value is set and the deviation signal is input, and outputs a first increase command signal or a decrease signal depending on whether the deviation signal is larger or smaller than the set value; and the first rise command. A signal and a lowering signal are input, and when the position of the electrode is below the lower limit position, a signal line cutoff section is set that does not allow the first ascending command signal and the lowering signal to pass, and a reference value is set and the deviation signal is input. , an electrode rise command section that outputs a second rise command signal when this deviation signal exceeds the reference value, and a first rise command signal that has passed through the signal line break section or is output from the electrode rise command section. a signal processing unit that outputs a raise signal when any of the second raise command signals is input; and a signal processor that drives the electrode upward when the raise signal is input from the signal processor and interrupts the signal an electrode drive mechanism that drives the electrode downward when a lowering signal passed through the section is input, and the adjusting section controls the first raising command signal or the lowering signal so that the deviation signal becomes equal to the set value. The method is characterized in that the position of the electrode is controlled by outputting a signal.

However, by configuring like this,
When the electrode current increases more than the reference value with the electrode reaching the lower limit position, a second ascending command signal is automatically output from the electrode ascending command section to the signal processing section, and from there a rising signal is sent to the electrode drive mechanism. As a result, the electrode is automatically pulled up and arc heating continues without any manual intervention, resulting in an electrode control device for arc furnaces that is effective in improving the operational efficiency of arc furnaces. This is what I did.

[Example of idea]

FIG. 1 is a block diagram of an embodiment of the present invention, and the figure also shows an arc furnace 1 etc. for convenience of explanation. In the figure, 1 is an arc furnace for steelmaking, etc. into which a heated object 2 such as scrap is charged, and 3 is an arc furnace 1.
A carbon cylindrical electrode for an arc furnace is inserted from above, and 4 is an arc formed by one phase of the three-phase AC voltage applied between the object to be heated 2 and the electrode 3. It is. Although only one electrode 3 is shown in the figure, three electrodes are actually inserted into the arc furnace 1 so as to correspond to the three-phase voltage. Reference numeral 5 denotes a power supply device that supplies electric power to the arc furnace 1 via the electrode 3, and includes a shield breaker, a furnace transformer, etc., and 6 detects the voltage applied to the electrode 3 and responds to this applied voltage. A voltage detector outputting a first signal (voltage signal) 6a, 7 is an electrode 3
This is a current detector that detects the current flowing through the circuit and outputs a second signal (current signal) 7a corresponding to this current.
8 receives the first signal 6a and the second signal 7a,
Calculate the electrode current command value Is using the applied voltage of the electrode 3 corresponding to the signal 6a and a predetermined impedance,
A deviation calculating section 9 outputs a deviation signal 8a according to the deviation of the current flowing through the electrode 3 with respect to this current command value Is, and 9 is an input of the deviation signal 8a, and a first rising command signal 9a or a lowering signal is input according to this input signal. 9b
This is an adjustment section that outputs the control signal 10 as a control signal 10. 1
3, when the up signal 12a is input, the electrode 3 is driven upward to increase the length of the arc 4 and reduce the current flowing through the electrode 3, and when the down signal 9
When b is input, the electrode drive mechanism drives the electrode 3 downward to shorten the length of the arc 4 and increase the current flowing through the electrode 3. It is configured to be supported by a beam 13a and driven in the vertical direction by the drive mechanism. 11a and 11b are both limit switches built into the electrode drive mechanism 13, and are configured to open the circuit when the electrode 3 falls below the lower limit position. A signal 9b inputted to the signal processing section 12 and outputted from the adjustment section 9 is inputted to the electrode drive mechanism 13 via a limit switch 11b. 14, a reference value (for example, zero in this example) is set and a deviation signal 8a is inputted, and when this deviation signal 8a is, for example, larger than the reference value zero, that is, positive, in other words, the electrode 3 is energized. The actual current value is the current command value Is mentioned above.
The signal processing section 12 outputs the second ascending command signal 14a to the signal processing section 12 when the signal is larger than the first ascending command signal 9a and the second ascending command signal 14. is configured to output a raise signal 12a to the electrode drive mechanism 13 even if the signal is input. 15 is the above-mentioned deviation calculation section 8, adjustment section 9, and switches 11a and 11a.
and a signal processing section 12.
, an electrode drive mechanism 13 , and an electrode elevation command section 14
This is an electrode control device for an arc furnace consisting of the following.

Since the electrode control device 15 is configured as described above, the object 2 to be heated is melted by the arc 4 in the arc furnace 1 while the electrode 3 has not reached the lower limit position. As the length increases, the current flowing through the electrode 3 becomes smaller, so the deviation signal 8a
becomes negative, and in this case, the adjustment section 9 outputs a lowering signal 9
b is output and this signal is the limit switch 11.
This is input to the electrode drive mechanism 13 via b, and as a result, the electrode 3 falls and the arc 4 becomes shorter, so that the deviation signal 8a eventually becomes the set value zero, that is, the electrode current 6a becomes equal to the current command value Is. The adjustment section 9 is configured as follows. Further, the adjustment section 9 outputs a positive deviation signal 8a when the length of the arc 4 becomes shorter and the current flowing through the electrode 3 increases, and when such a positive deviation signal 8a is input, the adjustment section 9 outputs a first ascending command signal 9a. This signal is inputted to the signal processing section 12 via the limit switch 11a, and as a result, a raise signal is inputted from the processing section 12 to the electrode drive mechanism 13, causing the electrode 3 to rise, so that the arc 4 becomes longer. In this case as well, the deviation signal 8a
is configured so that the set value is zero. That is, in FIG. 1, the adjustment section 9 adjusts the first rise command signal 9 so that the deviation signal 8a becomes equal to the set value zero.
The position of the electrode 3 is controlled by outputting a control signal 10 consisting of a signal a and a lowering signal 9b, and this control causes the arc current, that is, the current flowing through the electrode 3, to vary depending on the voltage applied to the electrode. However, as shown in the figure, when the object 2 to be heated melts and the electrode 3 gradually lowers and finally reaches the lower limit position, the limit switches 11a and 11b are both opened, so the signals 9a and 9b are both signals. The shear is cut at the sheath section 11. Therefore, if such a signal line or disconnection section 11 is provided, the electrode 3 will not be driven by the adjustment section 9 after the electrode 3 reaches the lower limit position. Accidents such as electrode breakage and hearth bottom damage due to collision with the hearth bottom will not occur. In this case, the limit switch 11a
is open, unmelted scrap falls from around the electrode 3, or an electrode other than the electrode 3 descends, increasing the current flowing through the electrode 3, and as a result, the deviation signal 8a increases. Even if the signal becomes positive and the first ascending command signal 9a is output from the adjustment section 9, this signal is cut off at the signal line break section 11, but on the other hand, in this case, the deviation signal 8a becomes positive and the electrode rises. Since the command unit 14 automatically outputs the second ascending command signal 14a, according to the electrode control device 15, if the current flowing through the electrode 3 increases after the electrode 3 reaches the lower limit position, the electrode 3 2 is automatically raised by the rising command signal 14a, and as a result, the limit switches 11a and 11b are both closed, so that from now on, the above-mentioned electrode position control when the electrode 3 is above the lower limit position is performed by the control device. Continued by 15. In other words, if the electrode control device 15 is used, the electrode 3 can be controlled without manual operation.
is raised from the lower limit position, the operating efficiency of the arc furnace 1 is improved.

In the above embodiment, if the deviation signal 8a becomes positive when the electrode 3 is above the lower limit position,
Although both the signal 9a and the signal 14a are input to the signal processing section 12, the signal processing section 12 is configured to output one rising signal 12a even in such an input state. Further, in the above-described embodiment, the adjustment section 9 and the electrode elevation command section 14 determine whether the deviation signal 8a is positive or negative, that is, the setting value and reference value for performing this determination operation are set to zero, and the signals 9a, 9b, 14a However, the present invention is not limited to such a configuration, and the setting value of the adjustment unit 9 for the deviation signal 8a and the reference value of the electrode elevation command unit 14 for the deviation signal 8a are finite. The value may be set to .

[Effect of idea]

As described above, according to the present invention, when the electrode current increases more than the reference value with the electrode reaching the lower limit position, the second ascending command signal is automatically output from the electrode ascending command section to the signal processing section. From there, a raising signal is output to the electrode drive mechanism, and eventually the electrode is automatically pulled up and arc heating continues without any manual intervention, which is effective in improving the operating efficiency of the arc furnace. This has the effect of providing an electrode control device for an arc furnace.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention. 1... Arc furnace, 3... Electrode, 6a... First signal, 7
a...Second signal, 8...Difference calculation section, 8a...Difference signal, 9...Adjustment section, 9a...First rise command signal, 9b
...Down signal, 10...Control signal, 11...Signal edge section, 12...Signal processing section, 12a...Up signal, 13
... Electrode drive mechanism, 14 ... Electrode elevation command section, 14a
...Second ascending command signal.

Claims (1)

[Claims for Utility Model Registration] A deviation signal between a current command value signal calculated from a voltage signal corresponding to the voltage applied to an electrode for an arc furnace and a predetermined impedance, and a current actual value signal corresponding to the current flowing through the electrode. a deviation calculation unit 8 which outputs a set value and receives the deviation signal, and outputs a first raising command signal or a lowering signal depending on whether the deviation signal is larger or smaller than the set value; an adjustment section 9; a signal line cutting section 11 into which the first up command signal and down signal are input and which does not allow the first up command signal and down signal to pass when the position of the electrode is below the lower limit position; a value is set and the deviation signal is input, and if this deviation signal exceeds the reference value, an electrode rise command section 14 outputs a second rise command signal.
and a signal processing unit 12 that outputs a rise signal when either the first rise command signal that has passed through the signal line break section or the second rise command signal output from the electrode rise command unit is input. , an electrode drive mechanism 13 that drives the electrode upward when the up signal is input from the signal processing section, and drives the electrode downward when the down signal that has passed through the signal line break section is input; , wherein the adjustment unit 9 controls the position of the electrode by outputting the first raising command signal or lowering signal so that the deviation signal becomes equal to the set value. Electrode control device.