LF Ladle Refining Furnace Electrode Control Strategy

1. Electrode adjustment control strategy

Combined with the needs of electrode adjustment and control, a PLC adjustment system equipped with switching and analog input and output templates can be used to realize current and voltage signal regulation and control, and to control the input and output of related switching quantities.
In terms of electrode lifting adjustment, it is necessary to complete the setting of the proportional coefficient of the independent impedance controller, and use the PI control algorithm to realize automatic adjustment to achieve the goal of automatically adjusting the electrode impedance. On the secondary side of the transformer, a voltage detection box can be connected to detect arc voltage, and a voltage transformer can be used to convert it into a standard signal.
At the intersection center point of the contact position between the ladle car wheel and the rail, the neutral point of the transformer can be set, and the detection box can be connected with a cable. Using the system's "power circle chart" tool, the optimal operating point for each gear can be calculated.
The operating point is located on the transformer tap curve, and the tap changer can be used to switch gears. The operating point on the tap circle line is determined based on the power factor and the intersection point of the power curve to adapt to different operating conditions.

2. Electrode protection control strategy

In terms of electrode control of LF ladle refining furnace, a variety of protection control strategies need to be adopted.
First, over-current protection needs to be implemented. When the arc current exceeds the maximum set value, the system over-current protection function is used to achieve simultaneous emergency lifting of the three-phase electrodes. The greater the arc current fed back by the electrode, the faster the lifting speed.
In current detection, there is a difference between the limit value and the arc current, and a PI regulator needs to be used for integral calculation to achieve output limitation and ensure that the three-phase electrode is in a reasonable motion state.
Through statistical analysis, the maximum three-phase electrode current can be determined, which is used to implement overcurrent control and avoid electrode overload problems. Secondly, the electrode short-circuit protection needs to be strengthened. When the impedance is lower than the minimum set value and the protection time is exceeded, the short-circuit control function needs to be automatically turned on.

3. Electrode monitoring and management strategy

Using a pressure transmitter, the pressure value in the hydraulic cylinder can be converted into a standard signal to achieve PLC chain control. When the steel slag is crusted on the liquid steel surface, the electrode cannot be lowered, and the hydraulic cylinder pressure continues to decrease, which may easily cause the electrode to break.
The regulating system detects that the pressure of a certain phase is lower than the set alarm value, and quickly raises the control electrode, and then drops it again to point the arc.
If arc lighting is unsuccessful for three consecutive times, the system will raise the three-phase electrode to a high position, and then issue an audible and visual alarm when the electrode contacts a non-conductive object.
During system operation, screen monitoring and analysis needs to be implemented. Combining the system monitoring data and display status, the parameters such as transformer gear position and voltage value can be set, so that automatic and manual state switching can be completed when the current reaches the maximum.
Based on the fault problems prompted on the screen, the system report data analysis can make the system operation properly optimized. For example, if the power transmission gear is optimized, a small current is used to preheat the cold electrode for the first power transmission to reduce thermal shock loss on the electrode surface.