JP6640566B2 - Arc furnace electrode lifting device - Google Patents

Description

  Embodiments of the present invention relate to an arc furnace electrode lifting and lowering device for rope making, which generates an arc discharge between an electrode and scrap to melt the scrap.

  In a three-phase AC arc furnace, the distance between the electrode and the scrap is controlled by raising and lowering the electrode by an arc furnace electrode lifting device. In an arc furnace electrode elevating device for steel making, limit switches are provided at upper and lower positions of an electrode supporting elevating mast which elevates and lowers integrally with an electrode, for protection of a mechanical system in electrode elevating control. In consideration of the failure of the upper limit switch and the lower limit switch, additional backup limit switches may be provided at positions higher than the upper limit switch or lower than the lower limit switch. is there.

  Due to the structure of the arc furnace, it may be difficult to provide a backup limit switch later. Also, it may be difficult to adjust the position of the attached limit switch. On the other hand, if the backup limit switch is not provided, when the limit switch fails, the electrode cannot be lifted and lowered even if the limit switch detection position is exceeded, which may cause damage to the mechanical system. is there.

JP-A-5-217671

  The embodiment provides an arc furnace electrode elevating device that enables protection of a mechanical system by backing up an upper limit switch and a lower limit switch without being restricted by hardware.

The arc furnace electrode lifting device according to the embodiment is provided on a lifting mast that is lifted and lowered integrally with the electrode, and is provided at an upper limit position where the electrode can move without damaging a mechanical system It is used in an arc furnace having a limit switch and a lower limit switch provided at a lower limit position where the electrode can move. The electrode raising and lowering device for an arc furnace includes an electrode moving distance calculating unit that outputs a moving distance of the electrode based on a rotation speed of a motor that moves the electrode up and down, and determines a position of the electrode based on the moving distance. An electrode position determining unit that outputs a stop signal for stopping the electrode; and a main control unit that stops the raising / lowering operation of the electrode based on the stop signal. The electrode position determination unit, when the moving distance is larger than a first threshold, or when the moving distance is smaller than a second threshold having a value smaller than the first threshold, The stop signal is output. The electrode position determination unit, when receiving an upper limit signal output when reaching the upper limit position of the movement of the electrode, set the position of the electrode to the upper limit position, the movement of the electrode. The position of the electrode is set to the lower limit position when a lower limit signal output when the lower limit position is reached is received.

  In the present embodiment, an electrode moving distance calculation unit that outputs the moving distance of the electrode based on the number of rotations of the electric motor, and a stop signal that determines the position of the electrode based on the moving distance of the electrode and stops the elevating operation of the electrode. Since the apparatus includes the output electrode position determination unit, the upper and lower positions of the electrode can be recognized and the raising and lowering operation of the electrode can be stopped without detecting the upper and lower limit signals. Therefore, the limit switch can be backed up without being restricted by hardware.

It is a block diagram which illustrates the arc furnace electrode raising / lowering apparatus which concerns on embodiment. It is a flowchart for demonstrating operation | movement of the arc furnace electrode raising / lowering apparatus of embodiment. It is a block diagram which illustrates the arc furnace electrode raising / lowering apparatus of a comparative example. It is a block diagram which illustrates the arc furnace electrode lifting / lowering apparatus which concerns on 2nd Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The drawings are schematic or conceptual, and the relationship between the thickness and the width of each part, the size ratio between the parts, and the like are not necessarily the same as actual ones. In addition, even when the same part is represented, the dimensions and ratios may be represented differently depending on the drawings.
In the specification and the drawings of the present application, the same reference numerals are given to the same elements as those described above with respect to the already described drawings, and the detailed description will be appropriately omitted.

FIG. 1 is a block diagram illustrating an electrode raising / lowering device for an arc furnace according to an embodiment.
As shown in FIG. 1, the arc furnace electrode lifting device 10 of the present embodiment includes an electrode position determination unit 12, an electrode lifting master control unit 14, and an electrode moving distance calculation unit 18.

  First, a configuration of a three-phase AC arc furnace using the arc furnace electrode lifting device 10 will be described. In the three-phase AC arc furnace, a three-phase AC power supply (not shown) is connected to the furnace transformer 5, and the electrode 2 is connected to the secondary side of the furnace transformer 5. The electrode 2 is arranged to be separated upward from the scrap 4 charged in the furnace body 3. A current transformer 6 is built in the secondary side of the furnace transformer 5, and the secondary side of the current transformer 6 is connected to an arc furnace electrode lifting device 10. An auxiliary transformer 7 is connected to a secondary side of the furnace transformer 5, and a secondary side of the auxiliary transformer 7 is connected to an arc furnace electrode lifting device 10.

  An elevating mast (not shown) that is raised and lowered integrally with the electrode 2 is provided with an upper limit switch 20a and a lower limit switch 20b. The upper limit switch 20a is provided at an upper limit position ULs where the electrode 2 can move without damaging the mechanical system. The upper limit switch 20a outputs an upper limit signal SUL when the electrode 2 reaches the upper limit position ULs. The lower limit switch 20b is provided at a lower limit position LLs where the electrode 2 can move without damaging the mechanical system. The lower limit switch 20b outputs a lower limit signal SLL when the electrode 2 reaches the position of the lower limit switch 20b.

  The electrode 2 is moved up and down by a motor 22 and a lifting drive system 23. In the normal operation of the arc furnace electrode elevating device 10, the electrode 2 moves up and down between the upper limit position ULs and the lower limit position LLs. The electric motor 22 is, for example, an induction motor, and is driven by an output of the arc furnace electrode lifting device 10.

  In order to detect the rotation speed of the motor 22, an electrode lifting / lowering motor rotation speed detection circuit 24 is provided. The electrode lifting / lowering motor rotation speed detection circuit 24 is, for example, a resolver or the like. The electrode lifting / lowering motor rotation speed detection circuit 24 detects the rotation speed of the motor 22, converts the rotation speed into a predetermined data format, and outputs the data to the arc furnace electrode lifting / lowering device 10.

  The arc furnace electrode elevating device 10 has a constant current-voltage ratio in accordance with the drooping characteristics of the load, based on the arc current flowing between the electrode 2 and the scrap 4 and the arc voltage between the electrode 2 and the scrap 4. Impedance constant control is performed as described above. The arc furnace electrode elevating device 10 controls the position of the electrode 2 via the electric motor 22 and the elevating drive system 23 by performing constant impedance control.

  When receiving the upper limit signal SUL or the lower limit signal SLL, the arc furnace electrode lifting device 10 stops the lifting control of the electrode 2. Further, as described later, when the arc furnace electrode lifting / lowering device 10 determines that the electrode 2 has reached the upper limit position ULs or the lower limit position LLs when neither the upper limit signal SUL nor the lower limit signal SLL is received, The lifting control of the electrode 2 is stopped.

  In the arc furnace in which the arc furnace electrode lifting device 10 is used, each of the three-phase electrodes connected to each phase of the three-phase AC power supply generates an arc discharge with the scrap 4 and is charged into the furnace body 3. The scrap 4 is melted. The distance between the electrode 2 of each phase of the three-phase alternating current and the scrap 4 is controlled independently. That is, in the arc furnace, the elevating mechanism of the electrode 2 is controlled by the arc furnace electrode elevating device 10. In the following, the lifting mechanism and the arc furnace electrode lifting device 10 for one of the three phases will be described unless otherwise specified.

The configuration of the arc furnace electrode lifting device 10 will be described.
The electrode position determination unit 12 is connected to the upper limit switch 20a and the lower limit switch 20b. The electrode position determination unit 12 is connected to the electrode movement distance calculation unit 18. The electrode position determination unit 12 receives the upper limit signal SUL, the lower limit signal SLL, and the moving distance Lm of the electrode 2, and determines the position Po of the electrode 2 based on these values. The electrode position determination unit 12 generates a stop signal Sstop for stopping the raising / lowering operation of the electrode 2 when reaching the upper limit position ULs and the lower limit position LLs or a position corresponding thereto according to the determination result of the position Po of the electrode 2. Generate.

  The electrode elevation master control unit 14 is connected to the secondary side of the current transformer 6 and the secondary side of the auxiliary transformer 7. The electrode elevation master control unit 14 inputs a current value I corresponding to the arc current from the current transformer 6 and a voltage value V corresponding to the arc voltage from the auxiliary transformer 7, and based on these inputs, the electrode 2-scrap 4 Calculate the impedance of the inter-arc discharge. The calculated impedance is controlled to be constant, and the electrode lifting master control unit 14 generates a speed command value F for controlling the position of the electrode 2. The output of the electrode lifting master control unit 14 is connected to an electrode lifting motor driving unit 16 and supplies a speed command value F to the electrode lifting motor driving unit 16.

  The electrode elevation master control unit 14 is connected to the electrode position determination unit 12. When receiving the stop signal Sstop from the electrode position determination unit 12, the electrode lifting master control unit 14 outputs a speed command value F0 for stopping the electric motor 22. The speed command value F0 for stopping the electric motor 22 is, for example, “0”. The electrode lifting master control unit 14 may stop the output to the motor drive unit 16 when receiving the stop signal Sstop.

  The electrode lifting / lowering motor driving unit 16 outputs a driving signal T for the motor 22 according to the speed command value F supplied from the electrode lifting / lowering master control unit 14. The electrode lifting / lowering motor drive unit 16 is, for example, an inverter device.

  The electrode moving distance calculation unit 18 is connected to the electrode lifting / lowering motor rotation speed detection circuit 24. The electrode moving distance calculator 18 is connected to the electrode position determiner 12. The electrode moving distance calculation unit 18 calculates the moving distance Lm of the electrode 2 from the rotation speed N of the electric motor 22 output from the electrode lifting / lowering motor rotation speed detection circuit 24. Hereinafter, a case where the electrode 2 moves in a direction away from the scrap 4 is defined as a positive moving distance Lm, and a case where the electrode 2 moves in a direction approaching the scrap 4 is defined as a negative moving distance Lm.

The operation of the arc furnace electrode elevating device 10 of the present embodiment will be described.
FIG. 2 is a flowchart for explaining the operation of the arc furnace electrode lifting device of the embodiment.
As shown in FIG. 2, in step S1, the electrode position determination unit 12 determines whether an upper limit signal SUL or a lower limit signal SLL has been received. The upper limit signal SUL is output from the upper limit switch 20a when the electrode 2 moves upward and reaches the upper limit position SUL. The lower limit signal SLL is output from the lower limit switch 20b when the electrode 2 moves downward and reaches the lower limit position LLs. When receiving the upper limit signal SUL or the lower limit signal SLL, the electrode position determination unit 12 shifts the processing to step S2.

  In step S2, when receiving the upper limit signal SUL, the electrode position determination unit 12 sets the position Po of the electrode 2 to the upper limit position ULs. When receiving the lower limit signal SLL, the electrode position determination unit 12 sets the position Po of the electrode 2 to the lower limit position LLs. By receiving the upper limit signal SUL or the lower limit signal SLL and setting the position Po of the electrode 2 to the above-described position, it is possible to correct the error of the moving distance Lm calculated based on the rotation speed N of the electric motor 22. it can.

  In step S3, the electrode position determination unit 12 sets the position Po of the electrode 2, and outputs a stop signal Sstop for stopping the elevating operation of the electrode 2. The electrode raising / lowering master control unit 14 that has received the stop signal Sstop supplies a speed command value F0 for stopping the motor 22 to the electrode lifting / lowering motor driving unit 16. Therefore, the raising / lowering operation of the electrode 2 stops.

  If the electrode position determination unit 12 does not receive any of the upper limit signal SUL and the lower limit signal SLL in step S1, the process proceeds to step S4. In step S4, the electrode position determination unit 12 determines whether the calculated position Po is below the upper limit position ULs. If the position Po is lower than the upper limit position ULs, the process proceeds to the next step S5.

  In step S5, the electrode position determination unit 12 determines whether the calculated position Po is above the lower limit position LLs. If the position Po is above the lower limit position LLs, the process returns to step S1.

  When the electrode 2 moves up and down between the upper limit position ULs and the lower limit position LLs, the above-described loop is repeatedly executed.

  If the position Po of the electrode 2 is not below the upper limit position ULs in step S4, the process proceeds to step S6. When a transition is made to step S6, the timer starts operating. This timer continues to operate until the position Po of the electrode 2 becomes lower than the upper limit position ULs. In step S6, the electrode position determination unit 12 determines whether the operation time of the timer has exceeded a preset time (timeout time) Tout. When the operation time of the timer exceeds the timeout time Tout, in step S7, the electrode position determination unit 12 outputs a stop signal Sstop. The electrode raising / lowering master control unit 14 that has received the stop signal Sstop supplies the speed command value F0 to the electrode lifting / lowering motor driving unit 16 to stop the motor 22. The electrode 2 stops the elevating operation.

  When the operation time of the timer does not exceed the timeout time Tout, the electrode position determination unit 12 returns to Step S4 to determine the position Po. If the position Po of the electrode 2 falls below the upper limit position ULs in step S4 before the timeout time Tout has elapsed, the timer is stopped and reset.

  If the position Po of the electrode 2 is not higher than the lower limit position LLs in step S5, the process shifts to step S8. When the process proceeds to step S8, the timer starts operating. This timer continues to operate until the position Po becomes higher than the lower limit position LLs. In step S8, the electrode position determination unit 12 determines whether the operation time of the timer has exceeded the timeout time Tout. When the operation time of the timer exceeds the timeout time Tout, the process proceeds to step S9, and the electrode position determination unit 12 outputs a stop signal Sstop. The electrode lifting master control unit 14 that has received the stop signal Sstop supplies the speed command value F0 to the electrode lifting motor driving unit 16 and stops the motor 22. The electrode 2 stops the elevating operation.

  If the operation time of the timer does not exceed the timeout time Tout, the process returns to step S5 to determine the position Po. Here, when the position Po of the electrode 2 becomes higher than the lower limit position LLs in step S5 before the timeout time Tout has elapsed, the timer is stopped and reset. Note that the timeout time of the timer operating in step S6 and the timeout time of the timer operating in step S8 may be the same or different.

  When detecting the arrival of the electrode 2 at the upper limit position ULs or the lower limit position LLs based on the moving distance Lm output from the electrode moving distance calculating unit 18, a timer is used to eliminate erroneous detection due to noise or the like. And the protection of the elevating operation can be safely performed.

The operation and effect of the arc furnace electrode lifting device 10 of the present embodiment will be described in comparison with the arc furnace electrode lifting device 110 of the comparative example.
FIG. 3 is a block diagram illustrating an arc furnace electrode elevating device 110 of a comparative example. The arc furnace electrode lifting device 110 of the comparative example is different from the arc furnace electrode lifting device 10 of the present embodiment in that it does not have an electrode position determination unit and an electrode moving distance calculation circuit.
As shown in FIG. 3, in the arc furnace electrode lifting device 110 of the comparative example, the electrode lifting master control unit 114 calculates the impedance based on the current value I corresponding to the arc current and the voltage value V corresponding to the arc voltage. Then, the position of the electrode 2 is controlled so that the deviation from the reference impedance becomes zero. When receiving the upper limit signal SUL, the electrode raising / lowering master control unit 114 stops the control in the upward direction and outputs a control signal in the downward direction. When the lower limit signal SLL is received, the control in the descending direction is stopped, and a control signal in the ascending direction is output.

  On the other hand, when a failure occurs in the upper limit switch 20a or the lower limit switch 20b, the upper limit signal SUL or the lower limit signal SLL despite the electrode 2 reaching the upper limit position ULs or the lower limit position LLs. Might not be output. Since the electrode lifting master control unit 114 cannot output a control signal based on the upper limit signal SUL and the lower limit signal SLL, the electrode 2 continues the lifting operation beyond the upper limit position ULs and the lower limit position LLs. . As a result, the mechanical system of the AC arc furnace may be damaged. As described above, providing a backup limit switch further above and below for backup due to a failure of the limit switch or the like is difficult due to a significant change in the control system, or is physically difficult. In some cases, it is difficult to add to

  On the other hand, in the arc furnace electrode elevating device 10 of the present embodiment, the position Po of the electrode 2 is calculated based on the output of the electrode moving distance calculation unit 18 to determine whether the position Po of the electrode 2 is appropriate. Is provided. Therefore, in the arc furnace electrode elevating device 10, the limit switch can be backed up without adding a limit switch as hardware. In the arc furnace electrode elevating device 10 of the present embodiment, since no hardware is added, the position where the electrode 2 is stopped or the set value corresponding to the position where the electrode 2 is stopped can be arbitrarily set. For example, since the stop position of the electrode 2 can be provided further above the upper limit position ULs or further below the lower limit position LLs, an optimum protection system can be constructed according to the circumstances of the plant.

  According to the embodiment described above, it is possible to realize an arc furnace electrode elevating device capable of protecting a mechanical system by performing backup of an upper limit switch and a lower limit switch without considering hardware restrictions. Can be.

  Although some embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalents thereof. The above-described embodiments can be implemented in combination with each other.

2 electrode, 3 furnace body, 4 scraps, 5 furnace transformer, 6 current transformer, 7 auxiliary transformer, 10 arc furnace electrode lifting / lowering device, 12 electrode position determination unit, 14 electrode lifting / main control unit, 16 electrode lifting / lowering motor Drive unit, 18 electrode moving distance calculation unit, 20a upper limit switch, 20b lower limit switch, 22 motor, 23 lifting drive system, 24 electrode lifting motor rotation speed detection circuit

Claims (2)

An upper limit switch and an upper limit switch provided at an upper limit position at which the electrode can be moved without damaging a mechanical system are provided on a lifting mast which is lifted and lowered integrally with the electrode. An arc furnace electrode lifting device for an arc furnace having a lower limit switch provided at a lower limit position,
An electrode moving distance calculation unit that outputs a moving distance of the electrode based on a rotation speed of a motor that moves the electrode up and down,
An electrode position determination unit that determines a position of the electrode based on the moving distance and outputs a stop signal to stop the electrode.
Based on the stop signal, a main control unit that stops the elevating operation of the electrode,
With
The electrode position determination unit,
Outputting the stop signal when the moving distance is larger than a first threshold value or when the moving distance is smaller than a second threshold value having a value smaller than the first threshold value;
When receiving the upper limit signal output by the upper limit switch when reaching the upper limit position of the movement of the electrode, set the position of the electrode to the upper limit position, the lower limit position of the movement of the electrode. An arc furnace electrode elevating device for setting the position of the electrode to the lower limit position when receiving a lower limit signal output from the lower limit switch when the lower limit switch is reached.   The electrode position determination unit outputs the stop signal when the moving distance exceeds the first threshold value for more than a first time, and the second threshold value when the moving distance exceeds a second time. 2. The arc furnace electrode lifting device according to claim 1, wherein the stop signal is output when the stop signal is smaller than a value.

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