Application of the hottest Mitsubishi frequency co

2022-08-15
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Application of Mitsubishi frequency converter in the efficient transformation of billet caster

abstract; This paper expounds the characteristics of fr-a240e frequency converter and the composition of AC frequency conversion speed regulation control system, and focuses on the setting of acceleration and deceleration parameters and the anti-interference measures of the frequency converter

key words: characteristic control system parameter setting anti-interference

1 Overview

compared with the traditional continuous caster, the high-efficiency continuous caster technology, with its advantages of high casting speed, high operation rate and high quality, is actually not like the "said in an article (aluminum China 2016, issue 2, page 10) in China in recent years; It can also produce 2000 and 7000 series alloys rdquo; With rapid development. The transformation of high-efficiency billet caster in China is a key scientific research project in the ninth five year plan. Many successful experiences have been summarized from several years of practice. The casting speed of 150 square billets has reached 3.0m/min, and the quality of billets has also been greatly improved. Laiwu Iron and Steel Co., Ltd. has three small billet casters. After investigation and demonstration, the 2# small billet casters have been effectively transformed. In the speed regulation system of mold vibration and tension leveler driving machine, the originally designed DC system is transformed into AC frequency conversion speed regulation system. Fr-a240e frequency converter with high performance and ultra-low noise is selected based on the process characteristics of continuous caster crystallizer vibration and tension leveler

- a240e frequency converter characteristics

continuous caster crystallizer vibration device and tension leveler are the main equipment of continuous caster, and the transmission control level is required to be high. Because the DC motor of the originally designed DC speed regulation system works under adverse conditions, its failure rate and maintenance rate are high, which directly affects the production rate and product quality of continuous caster. With the improvement of AC frequency conversion technology, the application of frequency conversion technology in continuous caster crystallizer vibration device and tension leveler has become an inevitable trend. Because fr-a240e series frequency converter has high performance, ultra-low noise and other characteristics, it is selected in the high-efficiency transformation of 2# continuous casting machine. Compared with general frequency converter, it has the following characteristics:

2.1 selection of applicable load

fr-a240e frequency converter has the output characteristics (v/f) selected according to the load characteristics, which is suitable for constant torque loads, such as conveyors, trolleys, etc., and also suitable for loads with elevator characteristics. It has the torque lifting function, adjusts the torque of the motor in the low-frequency area, and makes its output characteristics match with the load characteristics, so that the system has high dynamic quality characteristics

2.2 flux vector control

when large starting torque or full low-speed torque is required and the load changes sharply, its flux control function should be selected. The starting torque of this function can reach 150%/1hz, and in the high-speed area, the vector control can also operate with weak magnetic field for constant power speed regulation. Its speed torque accuracy can respond to the frequency performance and index, which can reach the quality index of DC speed regulation system

2.3 restart characteristics after instant stop

the instant stop and restart of the system is also a very important function for the transmission of the state. Because in the absence of magnetic field, the gradual rising curve or instantaneous speed is selected to estimate, otherwise the Chinese plastic extruder market will also have a lot of progress and breakthrough to monitor the setting of its free running time. In order to adapt to the inertia (GD) of the load, the torque can be adjusted within the range of 0.1-5s, The rising time of restart is also adjusted within the range of 0.1-5s according to the inertia and torque of the load, and the rising time of restart control output voltage

2.4 ultra low noise characteristics

the noise includes the noise that invades from the outside to make the frequency converter malfunction and the noise that the frequency converter radiates to make the peripheral equipment malfunction. In order to reduce the noise terminal voltage, the fr-a240e series frequency converter can change the carrier frequency according to the relationship between the resonance frequency of the mechanical system and the motor. When the PWM carrier frequency is reduced, the noise and leakage current emitted by the frequency converter will be reduced

3. The control system of crystallizer vibration and tension leveler

2 # continuous casting machine is composed of five Siemens S7 Series PLCs (each casting stream is automatically controlled by one S7-PLC, and the public equipment is controlled by one S7-PLC). The profibs-df bus system is adopted, and the programmer communicates with the MMI system through the communication module cp443-5. The mold vibration of the casting flow and the AC variable frequency speed regulation system of the tension leveler are incorporated into the PLC system to realize the automatic control of the production process of the continuous caster

3.1 mold vibration control system

the mold vibration AC speed regulation system composed of frequency converter has two operation modes, one is manual operation on the console, the other is full-automatic operation by PLC Manual and automatic selection can be realized on the console in the control room. During manual operation, the vibration frequency (motor speed) of the vibration device can be given manually on the console, and the start and stop of the motor can be controlled on the local control box of the operation platform. This mode is set for the maintenance and commissioning of equipment, while the normal production of continuous casting machine is to select the automatic mode. At this time, the vibration motor starts and stops automatically with the start and stop of the tension leveler. The vibration frequency of the crystallizer changes linearly according to the speed of the tension leveler, and its linear relationship is given by the continuous casting process

3.2 the control system of the tension leveler

the control system of the tension leveler is mainly responsible for the speed adjustment of ingot feeding, starting, blank drawing and stopping of the tension leveler, as well as the pressing and lifting functions of the first and second rollers of the tension leveler. Its operation right is on the console of the control room. Selecting manual can only realize the inching operation of the tension leveler, and the tension leveler operates slowly upward or downward at the speed value set in advance on the frequency converter. During automatic operation, PLC can quickly accelerate the tension leveler to the rated speed during ingot feeding according to the set process parameters. In the whole billet drawing process, the frequency converter can automatically adjust the speed according to the given value from PLC, so as to ensure that the billet drawing speed operates on the given parameter value of the process, so as to realize the full automatic control of the continuous casting production process

4. The setting of acceleration and deceleration parameters

the tension leveler and crystallizer vibration system generally require rapid startup. If the value of TQG is too large to meet the requirements of starting speed, it is necessary to increase the MD, which requires to increase the capacity of the motor, and the capacity of the frequency converter should also be increased accordingly. If the deceleration time is shortened, the regenerative braking components should be configured outside the frequency converter, so that the performance price ratio of the system will be reduced. Therefore, the acceleration and deceleration time of the system is an important parameter of the system

4.1 setting of acceleration time

the acceleration time of frequency converter refers to the time required for the frequency of the system to rise from 0 to 50Hz, that is, the time required for the motor to rise from zero speed to rated speed, and the time TQG required for the motor to rise from zero speed to working speed ng. TQG is calculated according to the following formula:

tqg=gd2ng/375 (md---mj)

MD - acceleration torque of the motor, which is taken as (1.2-1.3) me during calculation, and me is the rated torque of the motor

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