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Application of Siemens high-efficiency frequency converter in blast furnace automatic control system

Abstract: This paper introduces the application of Siemens 6SE70 frequency converter in blast furnace automatic control system. The blast furnace charging system uses modern computer technology to closely combine the PLC system with the frequency converter system, realize the unity of PLC and frequency converter control, and solve the problems of wind shutdown and shutdown caused by the instability of the winch control system. The stability of the winch feeding system is improved and the failure rate of the feeding system is reduced. The flexible application of high-efficiency frequency converter has become the basis for stable and high-yield production of blast furnace

key words: frequency converter blast furnace charging winch PLC I. blast furnace winch charging and distribution process introduction blast furnace charging mainly has two forms: one is winch charging, and the other is belt charging. Because the charging area of the charging car is small, it is widely used in small and medium-sized blast furnaces, For example, the winch system of medium-sized blast furnace adopts double motor control, and then through the movement of the beam of the experimental machine, the loading system, which is very helpful for our research and development project, and the small blast furnace adopts single motor control. The main process of the winch feeding system is: various raw materials are put into the intermediate hopper after being batched under the trough. After the hopper car arrives at the pit, the intermediate bucket puts the materials into the hopper car. After the gate of the intermediate bucket is closed in place and the furnace top is ready, the hopper car starts, and reaches the furnace top through acceleration - constant speed (high speed) - deceleration 1 - deceleration 2. 2、 Control system scheme 2.1 main electrical equipment of charging and furnace top system

1, AC motor power of winch mechanism 160kW, one set of three-phase AC 380V

2. A cooling fan motor of 3.7KW, three-phase AC 380V

3. Two charging car brakes of 1kW, two-phase AC 380V

4. Skip travel encoder, one Omron

5. One intelligent master controller

6. One side of the charging car switching cabinet, AC frequency conversion to promote the development, production and utilization of ceramic aluminum new materials in diesel engines and their parts, one integrated transmission cabinet, two sides, one for use and one for standby, and one side of the braking resistor cabinet

7. Two Siemens 6SE70 200kW frequency converters are selected for the charging car, with supporting braking units

8. PLC configuration is shown in the table: cpu414 6ES7 xgab0 only 1 di 32-point DC24V 6ES7 421-1bl00-0aa0 only 6 do 32-point DC24V 6ES7 422-1bl00-0aa0 only 3 analog quantity AI 8-point 6ES7 431-1kf10-0ab0 only 2 analog quantity Ao 6ES7 432-1hf10-0ab0 only 12.2 basic process requirements

1. Skip Winch: the skip winch operates according to the skip travel curve

2. Meet the requirements of high, medium and low speed speed regulation under the manual mode of PLC and console

3. The starting, stopping, acceleration and deceleration of the hopper car should be stable, and the speed control is less affected by the load (no-load or full load)

4. The main winch is equipped with wire rope relaxation protection and limit tension protection device (overcurrent protection)

5. The hopper car has a travel limit, over limit protection device, and low-speed inspection protection

6. Reel reverse protection when the skip has not reached the end of the journey; Under the condition of truck, it is allowed to stop or descend under control. 2.3 the design scheme

system block diagram is shown in Figure 1, (1) frequency conversion and speed regulation device of main winch

we use 6SE70 full digital AC frequency conversion and speed regulation power supply device of Siemens company. The system is equipped with supporting braking unit and independent braking resistance cabinet, and adopts energy consumption braking to realize the braking of winch system. The working mode of the power supply device is one for standby and one for use, and the standby switching is completed through the three pole double throw switch in the switching cabinet. The control signal of each frequency converter completes the basic interlocking and control through the electrical equipment of the switching cabinet. The relay is used to isolate between the main PLC and the switching cabinet, and between the operation console and the switching cabinet, so that the control of the charging car can be controlled by the PLC or the operation console respectively, so as to improve the reliability of the whole system. The holding brake realizes the holding brake control and interlock control during the operation of the charging car by the holding brake special control function in 6SE70 device

the AC incoming line of the speed regulating device is decoupled through the AC incoming reactor, and the incoming reactor is set in the power switching cabinet, which is equivalent to two sets of frequency converters sharing one incoming reactor. Two outgoing reactors are respectively connected behind the change-over switch to eliminate the high-order harmonics of the outgoing line and protect the motor

the positioning of the hopper car is completed by the absolute value encoder, and the signal is gray code, which is sent to PLC in the form of switching value; The master controller adopts an incremental encoder, and the pulse signal is sent to the internal Small PLC of the master controller. The skip positioning encoder is connected with PLC through PROFIBUS DP

(2) positioning of charging car

the traditional positioning method of blast furnace winch charging car is the mechanical master controller. At present, there are many problems in using graphene to a strategic height. The positioning accuracy is poor, the on-site environment is bad, and the mechanical contacts are easy to oxidize. After the position changes, you must stop the wind, run empty car for several times, and adjust the position of charging car. The scheme we are now using is to position the hopper car by combining the intelligent master controller with the encoder (PLC), and adjust the position of the hopper car through the digital panel. If the position of the hopper car changes, just change the value of the position of the hopper car on the digital panel to complete the positioning of the hopper car. At the same time, the data detected by the master controller is compared with the data in the master PLC. When the error is less than the allowable value, it is considered that the positioning is accurate

(3) introduction to the operation of the hopper car

the hopper car is at the bottom of the pit (the other hopper car is at the top), and the material is prepared