Application of frequency conversion and speed regu

2022-07-29
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Application of variable frequency speed regulation technology in sintering proportioning system of coking plant Overview

China is the world's largest coke producer. It is estimated that about 200million tons of high-quality coal are used to produce coke every year. According to incomplete statistics of Shanxi Province alone, the annual coking consumption of coal exceeds 90million tons. China's coke export directly affects the world market. In the traditional coking process, the adjustment mainly depends on work experience, and there are the following problems: (1) the proportioning cannot be adjusted in time, and the production efficiency is low. (2) Due to the lack of measuring equipment, there are many human factors, the materials can not be well controlled, the waste phenomenon is serious, the production cost is greatly increased, the unqualified rate is large, resulting in a large number of waste products. (3) Due to the serious dust pollution of materials, the health of workers is seriously affected. Automatic security protection in recent years;, Especially after China's entry into WTO, the industrial process automation is getting higher and higher and people's awareness of environmental protection is enhanced. Frequency conversion technology has been widely used at home and abroad for its excellent performance. This paper mainly introduces the application of variable frequency speed regulation technology in sintering batching system of coking plants of Hegang and Xingang

II. System process flow and main parameters

the sintering batching system of coking plant is mainly composed of industrial control computer (including configuration software), control system (including PLC, etc.), secondary instrument (including metering instrument and expert regulator), frequency converter (model vfd110a43a), field operation panel, speed regulating belt scale and disc feeder. The coke produced is mainly composed of limestone, coal, ferroalloy and sintered materials. The first three materials have two silos respectively. The materials in the silos are respectively fed into the general conveyor belt through their respective disc feeders and measured by the electronic batching belt weigher, and then sent to the general conveyor belt through the cooperation with Jiangsu Yihang Auto Parts Technology Co., Ltd Suzhou Bandung Auto Parts Co., Ltd. and other auto parts suppliers have cooperated for a long time with the general conveyor belt to send the mixture to the silo

main parameters

(1) disc feeder

motor model is ysp160mz-4, power 11kw, rotating speed 1140rpm, AC380V, 50Hz

(2) electronic batching belt scale

belt width: 1000mm; Speed: 0.5m/s; Production capacity: 60t/h (5 sets), 30t/h (2 sets)

III. process control implementation of the system

electronic speed regulating batching system usually has two speed regulating modes: regulating the feeding of disc feeder and regulating the feeding speed of belt conveyor. The system uses an adjustable disc feeder for feeding

the control process is mainly to measure the materials conveyed by the disc feeder through the electronic batching belt scale. The control instrument receives the weighing signal and speed signal, which are transformed into the accumulated value and instantaneous flow after processing, and the accumulated value and instantaneous flow signal are transmitted to the industrial control computer (upper computer) through the RS-485 port, and the 4 ~ 20mA analog current signal is transmitted to the PID regulator, After the regulator compares the signal with the internal set value, the 4 ~ 20mA analog signal is sent to the frequency converter, and then the frequency converter adjusts the rotating speed of the disc feeder. When the flow increases, the rotating speed of the disc feeder will be reduced, on the contrary, the rotating speed of many kinds of feeders under the disc will be increased, so that the flow and stage accumulation of several materials will be kept within the set range, so as to obtain reliable product quality

the parameters and operation process of the system can be set and monitored by the industrial computer, and the value of the PID regulator can also be manually modified. The operation is convenient and the control is reliable. The whole system has achieved a high degree of automation, forming seven relatively independent and interconnected closed-loop control systems

IV. design of frequency converter control system

1. The change of material quantity of the control object

is mainly determined by the rotating speed of the disc feeder, that is, the final control object of the system is the disc feeder. The rotating speed of the disc feeder is controlled by the frequency converter. When the capacity (d1+ D2) is greater than 13, the size deviation and appearance quality are unqualified, which is related to the selection specification of the frequency converter

2. Load characteristics

from the above control process, we can see that the frequency converter is used to control the disc feeder, its load belongs to constant torque load, and the motor power is proportional to the product of load torque and speed, that is, p=t*n/9550

3. Selection of frequency converter model

the motor model of disc feeder is ysp160mz-4, the power is 11kw, and its rated current is 25A. Since the system has been in continuous operation during operation, the rated output current of the frequency converter should be greater than (1..1) times the rated current of the motor. In normal operation, the uniformity of on-site materials is good, the acceleration and deceleration frequency of the motor is relatively low, and the acceleration and deceleration time is relatively short. Although the maximum output torque of the frequency converter is determined by the maximum output current of the frequency converter, according to the calculation results and design experience, we choose Delta's frequency converter, whose model and specification is vfd110a43a

4. Proportional adjustment mode

the materials on the belt are not uniform, and the instantaneous flow of materials is always changing. Therefore, the lower computer of the system adopts PID regulator. The regulator compares the flow signal sent by the upper computer with the given value, and outputs 4 ~ 20mA signal to adjust the frequency converter according to the deviation, so as to achieve a constant flow and achieve the desired effect

5. The internal parameter setting of the frequency converter

the main frequency input is adjusted by the PID regulator output of 4 ~ 20mA, and the external terminal is controlled by the two-wire connection method. The main parameter settings are: main frequency input pr00=1, operation command pr01=2, motor stop mode pr02=1, maximum frequency pr03=60, maximum voltage frequency pr04=50, maximum output voltage pr05=380, minimum frequency pr08=2, minimum output voltage pr09=10, external terminal control pr38=1

6. Motor power supply

the motor power supply adopts dual power supply: frequency converter power supply and bypass power supply. When the frequency converter fails or is cut off artificially, the motor will automatically switch to the bypass mode, and adjust the disc feeder according to the actual needs with reference to the current to run at a constant speed, so as to ensure the uninterrupted operation of the system and ensure that the control accuracy is within a certain range

v. precautions in the use of frequency converter

due to the poor on-site working environment of the batching system, once the use is incorrect or the setting is unreasonable, it will easily cause misoperation and failure of the frequency converter, which will not only fail to achieve the expected operation effect, but even damage the equipment

1. The frequency converter is subject to external electromagnetic interference

when the system is just put into use, the circuit often malfunctions, resulting in

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