Electrode lifting process control system of the ho

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AC electric arc furnace electrode lifting process control system

electrode lifting regulator is the key equipment of steel-making electric arc furnace. A good regulator plays a great role in reducing energy consumption, electrode consumption and equipment failure rate. This paper introduces an automatic control system for electrode lifting and lowering of hydraulic AC electric arc furnace based on the combination of industrial computer and single chip microcomputer

1 system configuration and function

system configuration structure

1.1 upper computer

the upper computer adopts the basic configuration of PC 486 DX integrated industrial control computer (LCD), which mainly realizes the necessity of waterproof materials. Now it adjusts and modifies various parameters, and dynamically displays parameters such as arc voltage and arc current

1.2 lower computer

the lower computer part is the main regulation system of the system, which is composed of three-phase (a, B, c) regulation board, power supply and digital display board, and power amplifier board. The crack expansion speed of three-phase regulating plate, power supply and digital display is close to that of the V-notch impact specimen, and the plate is broken by impact force. AT89C52 is used as the single chip microcomputer system

the arc current and arc voltage signals of each phase of the phase regulating board are transformed by the signal of LEM module, and the arc voltage signals of 0 ~ 300V and 0 ~ 5A are converted into standard signals of 0 ~ 5V respectively, and the given signal of arc current (0 ~ 15ka) is also changed into standard signals of 0 ~ 5V, which are input into the computer together. Single chip microcomputer converts them into digital quantities through a/D, and then makes D/a output voltage within ± 5V through impedance calculation and intelligent control algorithm, and then outputs ± 10V voltage through isolator and operational amplifier. In addition, the board is equipped with 485 driver chip MAX485, parameter memory EEPROM and microprocessor monitoring circuit

the power supply and the digital display board are displayed by the single chip microcomputer, and the data arc current from the adjustment board is given and displayed, and + 5V and + 24V voltages are provided to other boards of the system. MAX7219 is selected as the LED driver chip of this board to display the gear/gear voltage and given arc current with 4 bits and 2 rows of LEDs

the signal output by the phase adjustment board of the power amplifier drive board is processed by the high-voltage operational amplifier, and finally outputs 0 ~ 100mA current

1.3 characteristics of the system

(1) the upper computer adopts high-resolution large LCD, which is less affected by electromagnetic interference. (2) The input and output are completely isolated. Hall element (LEM) is used for arc voltage and arc current signals, and the transformer is abandoned. The linearity of LEM module is very good and the isolation voltage is up to 2500V, which not only ensures the accuracy of signal acquisition, but also protects the system when SCM manufactures different plastic products. The analog output adopts ISO 212 isolation of BB company, which makes the system have strong anti-interference ability. (3) The two-stage collecting and distributing structure is adopted, and there is no direct hardware connection between the A, B and C three-phase regulating boards. When one phase fails, the operation of the other two phases will not be affected

2 system software

the system has one upper computer program and two lower computer programs. In order to increase the flexibility of the system, the software of the single chip microcomputer system should be relatively independent of the specific electric arc furnace. When some control parameters need to be changed, it is not necessary to unplug the CPU of the single chip microcomputer to rewrite the program, but only to run the corresponding configuration program of the lower computer through the upper computer

2.1 upper computer program

the upper computer monitoring program dynamically displays the arc voltage, arc flow, given arc flow, smelting time and other parameter values and curves in the smelting process. The software is generated by InTouch configuration software package, and the generated configuration software realizes the real-time update of data through dynamic data exchange. The upper computer software also includes the parameter configuration program for the three-phase regulating board, which is only used during debugging

2.2 lower computer program

the lower computer program is divided into two parts: the phase regulation board program and the power supply and digital display board program, which are composed of the main program, the communication interrupt service program and the timing interrupt service program. The first part of the main program includes the processing of reading parameter values, receiving data and sending data from EEPROM, and the timing interrupt service program includes the processing of control process and control parameters

receiving data processing, the upper computer transmits the configuration parameters to the lower computer through RS-485 interface, and sends the corresponding command code data. After receiving these data, the lower computer writes them into EEPROM

send data processing to transmit the arc current given signal from RS-485 to the power supply, digital display board and upper computer, and also transmit the arc current, arc voltage, lifting direction, sensitivity and other signals to the upper computer

the control process processing realizes the state processing and automatic adjustment of the steel-making process, and fully takes into account the short circuit of waste materials and the collision of electrodes in the smelting process

the second part of the main program realizes the display of the given arc current, gear and gear voltage, which includes reading the gear contact signal, establishing the scientific and technological innovation system with the enterprise as the main body through RS new materials -485 communication mode, reading the arc current given value from the phase regulator board and displaying it on the LED, reading and writing the gear parameter value to the EEPROM, and regularly interrupting the service program to realize the update display of the given arc current value, and the alternating display of the gear and gear voltage value

3 operation results

after the system was put into operation at the beginning of 1997, it is easy to operate and reliable, the electrode consumption, energy consumption and failure rate have been greatly reduced, the arc ignition is easy in the melting period, the number of arc breaks is small, and the sensitivity in the reduction period is high

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