JPH062097U - Electrode arc short circuit detector in electric furnace - Google Patents

Abstract

(57) [Summary] [Purpose] By automatically detecting arc formation between electrodes and immediately performing prescribed processing, it is possible to fully automate the electric furnace and enable unattended operation of the electric furnace. [Structure] The position sensor 12 detects and records the electrode position at the moment when a regular arc is generated, and at the time of the next arc activation, it is detected that a current flows through the electrode at a position above the previously recorded electrode position. By doing so, the arc short circuit between the electrodes is detected.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an electric furnace in which a metal material in a furnace body is melted / heated by an arc, and in particular, the reliability of the operation of the electric furnace is improved by automatically detecting the occurrence of an arc that short-circuits between electrodes. The present invention relates to an inter-electrode arc short-circuit detection device in an electric furnace (hereinafter referred to as an arc furnace) that can be used.

[0002]

[Prior art]

 Arc furnaces for steelmaking, sludge melting furnaces, ladle furnaces that heat by arc, etc., to heat the molten metal stored in the furnace body for steelmaking, steelmaking, metal refining, alloy production, etc. An arc furnace is used that generates an arc between these metal materials and the electrode and uses the heat generated by the arc to melt the metal material such as scrap that has been thrown in. Such an arc furnace has, for example, a structure as shown in FIG. In FIG. 3, a metallic material 1 to be treated is stored in a furnace body 2. Electrodes 3a, 3b and 3c are respectively connected to a three-phase power source (not shown) supplied via a power transformer 4. Each of the electrodes 3a, 3b, 3c is configured to be movable up and down, and an example of the lifting mechanism is configured to be coupled to the lifting mechanism 5 and to be lifted by a motor 7 via a winch 6. In the figure, the elevation mechanism attached to the electrodes 3a and 3b is not shown. Further, the control of the electric motor 7, the control function of a three-phase power source (not shown), etc. are also omitted. In the arc furnace having the above-described structure, the metallic material 1 is charged into the furnace body 2 and a predetermined voltage is applied to each electrode 3a, 3b, 3c from a three-phase power source (not shown) to control the device ( Each electrode 3a, 3b, 3c is lowered toward the furnace body 2 by means of not shown). When the tip positions of the electrodes 3a, 3b, 3c approach a predetermined distance on the surface of the metal material 1, arcs a, b, c are formed between the tips of the electrodes 3a, 3b, 3c and the surface of the metal material 1. To be done. Therefore, a three-phase power source (not shown) causes a current to flow through each of the electrodes 3a, 3b, 3c and the metal material 1 to maintain an arc, and the metal material 1 is heated. Methods for controlling electrodes in an arc furnace include those disclosed in JP-A-61-285693 and JP-A-2-103891. The one disclosed in Japanese Patent Laid-Open No. 61-285693 is provided with a detector for detecting the state of material collapse from the signal of at least one of the electric power input to the furnace, the melting time of the material, and the voltage flicker. When the condition is detected, the electrode is pulled up to prevent a short circuit between the electrode and scrap due to raw material spillage. Japanese Patent Laid-Open No. 2-103891 discloses a thyristor rectifier in which an AC power supply is rectified by a thyristor rectifier and then converted into an AC power supply for arc by an inverter, and when the load current value becomes larger than a preset value. The ignition phase angle is automatically controlled to maintain the load current at the set value.

[0003]

[Problems to be solved by the device]

 By the way, in the arc furnace as described above, for example, each electrode 3a, 3b, 3c is lowered toward the furnace body 2 in a state in which an arc is easily formed depending on the atmospheric conditions in the furnace body and the like. An arc is generated between any of the electrodes before the regular arcs a, b, and c are formed, and, for example, an arc ab is formed between the electrodes 3a and 3b to short-circuit the electrodes. Sometimes. If an arc is formed between the electrodes, it is necessary to turn off the power once and restart the startup work. For this reason, monitoring by workers is required, which makes it impossible to fully automate the arc furnace, and also causes a decrease in the operating rate of the arc furnace when the discovery of arc formation between electrodes is delayed. Was there. Except for the above problems, the present invention enables the arc furnace to be fully automated by automatically detecting the arc formation between the electrodes and immediately taking prescribed measures, enabling unattended operation of the arc furnace. It is an object (problem) to provide an inter-electrode arc short circuit detection device in an arc furnace for the purpose of, for example,

[0004]

[Means for Solving the Problems] In order to solve the above problems, in an inter-electrode arc short-circuit detection device in an arc furnace according to the present invention, the position of an electrode at the moment when a regular arc is generated is detected and recorded by a position sensor. When the arc is started next time, an arc short circuit between electrodes is detected by detecting that the arc is generated above the previously recorded electrode position.

[0005]

[Action]

 In the present invention, as described above, the arc short circuit between electrodes is detected by detecting the arc generation above the electrode position where the normal arc is generated. Therefore, it is detected at the moment when the arc short circuit between electrodes occurs. can do.

[0006]

【Example】

 An example of applying the inter-electrode arc short-circuit detecting device in the arc furnace according to the present invention to the arc furnace described in FIG. 3 in the related art will be described in detail with reference to the drawings. FIG. 1 shows a situation in which one embodiment of the present invention is applied to FIG. The same elements and devices as those in FIG. 3 are denoted by the same reference numerals. In FIG. 1, reference numeral 1 denotes a metal material to be processed by this arc furnace, which is stored in a furnace body 2. Electrodes 3a, 3b and 3c are connected to a three-phase power source (not shown) via a high voltage circuit breaker 20 and a power source transformer 4. The electrodes 3a, 3b, 3c are respectively connected to the lifting mechanism 5 and are lifted by a motor 7 which is coupled to a winch winding mechanism 6 via a winch 6A by a coupling mechanism having a predetermined gear ratio. ing. In FIG. 1, the illustration of the lifting mechanism for the electrodes 3a and 3b is omitted as in FIG. A position sensor 12, for example, pulsin as means for measuring and detecting the electrode position corresponding to the structure of the mechanism for coupling with the winch winding mechanism 6 is coupled to the electric motor 7 at a predetermined place of the lifting device. The position sensor 12 is input to the control device 10 including the control drive function of the electric motor 7, and the electric motor 7 is controlled by the control device 10. The tip positions of the electrodes 3a, 3b, 3c are indicated by 3aa, 3ba, 3ca, respectively, and a, b, c indicate arcs generated between the electrodes 3a, 3b, 3c and the metal material 1, respectively. , Ab indicate arcs generated between the electrodes 3a and 3b.

Next, an outline of the control device 10 in the configuration of the arc furnace shown in FIG. 1 will be described with reference to FIG. In FIG. 2, reference numeral 1 denotes a metal material to be processed by this arc furnace, which is stored in a furnace body 2. Reference numeral 3 indicates the above-mentioned three electrodes 3a, 3b, 3c as a whole, and is connected to a three-phase power source (not shown) via a high voltage circuit breaker 20 and a secondary voltage variable power transformer 4. ing. The electrode 3 is configured to be moved up and down by an electric motor 7 which is connected to an elevating mechanism 5 and is connected to a winch winding mechanism 6 via a winch 6A. In FIG. 2, for convenience of explanation, the lifting mechanism 5 is illustrated so as to lift and lower each electrode 3 in common. A position sensor 12 for measuring and detecting an electrode position, for example, pulsin, is connected to the electric motor 7 corresponding to the structure of the mechanism for coupling with the winch winding mechanism. The position sensor 12 is connected to a sensor input circuit 16 provided in the controller 10 and set according to the type characteristics of the position sensor. Further, 13 is a current detector provided on a connection line connecting to each electrode as a means for detecting the arc generation, and is connected to the sensor input circuit 16. The sensor input circuit 16 is connected to the signal processing function 15, and the signal processing function 15 is connected to a storage function 17 for temporary recording as a storage means. The control device 10 is also provided with a position comparison means 18 which will be described in detail later, and the position comparison means 18 is functionally connected to the storage function 17. The signal processing function 15 is connected to the control driving function 19 of the electric motor 7, and the control driving function 19 is connected to the electric motor 7 to drive the electric motor 7 and raise and lower the electrode 3. Further, the signal processing function 15 operates the high voltage circuit breaker 20 to cut off the current supply to the electrode 3.

Next, the operation of the present invention in the above-mentioned configuration will be described. In the arc furnace having the above-mentioned configuration, when the metal material 1 is charged into the furnace body 2 and the operation of the arc furnace is started, a three-phase alternating voltage is applied to the electrodes 3a, 3b, 3c via the transformer 4. To be done. Power is supplied from the control drive function 19 to the electric motor 7 by the function of the signal processing function 15 to drive the electric motor 7. The rotation of the electric motor 7 causes the winch winding mechanism 6 to send the winch 6A to move the electrode 3 up and down mechanism 5. When lowered, the tips 3aa, 3ba, 3ca of each electrode approach the surface of the metal material 1. The elevating device 5 is activated to lower the electrodes 3, and the position signals output from the position sensor 12 during the lowering of each electrode 3 are converted by the sensor input circuit 16 into position signals that can be read by the signal processing function 15. It is input to the signal processing function 15. When the tips of the electrodes 3 approach the surface of the metal material 1 and satisfy a predetermined condition, arcs a, b, between the tips 3aa, 3ba, 3ca of the electrodes and the surface of the metal material 1 shown in FIG. c is formed, and heating of the metal material 1 is started. When each electrode 3 starts forming an arc with the metal material 1 as described above, and the signal processing function 15 detects the start of arc discharge from the current value detected by the current detector 13, the position sensor 12 at that timing is detected. The electrode position signal output from is recorded in the memory function 17. After the above operation, the arc discharge is continued and the operation of the arc furnace is executed. When the operation of the arc furnace is interrupted, each electrode 3 is raised, and then the descent is started again, and when the arc generation is confirmed in the signal processing function 15 as described above, the signal processing function 15 records in the memory function 17 first. The electrode position at the moment of the occurrence of the arc is read out, and the signal comparing means 18 compares the read electrode position with the current electrode position. Comparison results If it is judged that the current electrode position is lower than the memory electrode position within a predetermined error, it is assumed that the arc is generated normally, and this arc furnace continues to operate. To do. As a result of comparing the current electrode position with the electrode position read from the recording function, if it is determined that the current electrode position is above the memory electrode position, it is determined that an arc short between electrodes has occurred, and the high voltage circuit breaker 20 is made to function and the electric power transmission to each electrode 3 is stopped. Further, the signal processing function 15 reverses the drive of the electric motor 7 to raise the electrode 3 to a predetermined position and notifies the operator of the arc short circuit between the electrodes by a predetermined alarm function (not shown).

The above description is for the basic configuration and the basic operation in the embodiment of the present invention. For example, in FIG. 2, one position sensor for each electrode 3 is shown in total. However, as shown in Fig. 1, when each electrode is controlled and driven individually, position sensors are provided for each electrode and controlled individually. In that case, naturally, three input circuits of the position sensor input circuit 16 of the control device 10 are provided. Further, although the position sensor 12 is described as a pulsin, for example, any other sensor may be used, and in that case, the input circuit 16 is naturally set corresponding to the type characteristic of the position sensor 12. Further, although the position sensor 12 is described as being mounted on the electric motor 7, it may be mounted on an appropriate position of the lifting mechanism which can measure the position of the winch winding mechanism 6A and other electrodes and which is not contaminated by the metal material 1 or the like. Also, the case where the electrode 3 is lifted and lowered by the winch mechanism has been described, but the type structure of the position sensor and the mounting position may be set so that the electrode position can be accurately detected for other lift mechanisms as well. Also, the position sensor of the electrode may correspond to any position of the electrode, but it is of course necessary to take measures against the length variation due to wear of the electrode. Further, in correspondence with the control function of the entire arc furnace, the configuration of each element function described above and the necessary means based on the technical idea of the present invention may be appropriately executed by a control function that is arbitrarily combined.

[0010]

[Effect of device]

 Since the present invention is configured as described above, the following excellent effects are obtained. It can be detected at the moment when the arc short circuit between the electrodes occurs. It is possible to automatically detect arc short circuits between electrodes, enabling unattended operation of arc furnace equipment. Since the arc short circuit between the electrodes can be detected at the moment when it occurs, the work efficiency can be improved. By detecting a short circuit between the electrodes, the power supply is turned off to save energy. By detecting the arc short circuit between the electrodes, the furnace lid etc. are not affected and the safety is excellent.

[Brief description of drawings]

FIG. 1 is a configuration explanatory view for explaining a schematic configuration of an example of an arc furnace to which the present invention is applied.

FIG. 2 is a schematic block configuration diagram showing a control device for controlling the arc furnace shown in FIG. 1 based on the present invention.

FIG. 3 is a schematic configuration example diagram illustrating a schematic configuration of a conventional arc furnace.

[Explanation of symbols]

 1: Metal Material 2: Furnace Body 3, 3a, 3b, 3c: Electrode 6: Winch Winding Mechanism 7: Electric Motor 10: Control Device 12: Position Sensor 13: Arc Detection Means (Current Detector) 17: Storage Means Function) 18: Position comparison means 20: High voltage circuit breaker

Claims (1)

[Scope of utility model registration request] 1. An electrode which is connected to a three-phase power source and is configured to be movable up and down is brought close to a metal material in a furnace body, and an arc is generated between the electrode and the metal material to melt the metal material. In an electric furnace for heating or heating, a position sensor attached to a lifting device for each electrode, a means for detecting the generation of an arc, a means for recording the electrode position at the moment when the arc measured by the position sensor is generated, When the next arc is started, a position comparison means for comparing the measured value of the position sensor at the moment when the arc is generated with the electrode position measured by the recorded position sensor, and the comparison result is more than the recorded electrode position. If it is at the upper part, it is determined that an inter-electrode arc short-circuit has occurred and a predetermined measure is executed, and the inter-electrode arc short-circuit detection device in an electric furnace is characterized. .