The hottest powerflex700 frequency converter is us

  • Detail

Research and application of powerflex700 frequency converter in bridge crane

wound asynchronous motor, the electrical transmission of rotor series multi-level resistance is the most extensive transmission form of crane, and it is the simplest speed regulation scheme, but it has the following shortcomings:

1 When the series resistance is started step by step, it has a great impact on the crane steel structure

2. The starting current of the system is large, and the starting current is 3 ~ 6 times the rated current of the stator

3. The speed regulation performance is poor, the efficiency is low, and it is controlled by stages, with current impact. When the speed is less than half, the mechanical characteristics are soft, and it cannot work stably

4. The braking stop impact is large. The mechanical braking using electromagnetic braking is carried out at a higher speed. The braking inertia torque and braking current are large, and the short-term impact force is more than 3 times the load torque, which has a large impact on the steel structure of the whole crane

due to the existence of the above factors, there is a great impact on the surface quality of steel plate in Jigang medium plate plant, which has seriously affected the image of our products in the minds of customers. At the same time, due to poor speed regulation performance and poor controllability, it is very easy to damage the edge of thin gauge steel plate in the process of transportation, resulting in a large amount of funds for quality objection compensation

in the current control field, vector frequency conversion technology has been mature and has been widely used successfully. If this technology is introduced into the crown block of the new upper plate warehouse, it will bring the application effect of "once and for all" for the long-term operation in the future, and make this crown block a real "maintenance free" system, greatly reducing the maintenance cost and saving human resources. Therefore, based on the above considerations, it is decided to introduce vector frequency conversion control technology to the 20+20 ton crown block of Jigang medium plate plant

2. Application of ControlLogix System

according to the control requirements, we propose a solution using the ControlLogix System Integration Architecture. Design for high performance and scalability. It has multi processor, multi task, multi network and multi language; Various analog, discrete and special i/o; Maximum connectivity between workshop and information system; Features of advanced integration of sequence, process, transmission and motion control

the control system is a vector control speed regulation system composed of three parts: ControlLogix System mainframe, 1794flex i/o substation, touch screen, AB vector converter, AC variable frequency electrical test area, ypg355m-10 double shaft variable frequency motor. PLC mainly completes the control of vector converter and crane and trolley traverse converter. It receives the signals collected by 1794flex i/o substation of the operation console and transmits them to ControlLogix controller through DeviceNet Fieldbus. After the controller makes calculations, it sends them to ab vector converter through DeviceNet Fieldbus as a given signal. The touch screen is mainly responsible for communicating with PLC and monitoring the status of the whole control system. After receiving the given signal, the AB vector converter makes the speed and direction of the variable frequency drive motor according to the given size and positive and negative. The schematic diagram of electrical control system is shown in Figure 1

3. Use of incremental encoder

incremental rotary encoder consumes the bolt longitudinal axial force sequence and phase relationship when converting its angle code disk through two internal photosensitive acceptors, and obtains that the angular displacement of its angle code disk increases (positive direction) or decreases (negative direction)

because the crown block system is manually operated and changes according to the site conditions, it is not appropriate to select the absolute value encoder. For the incremental encoder, the wiring method is simple and the signal processing is convenient. The working voltage is 24VDC, and the return signal is pulse signal, which can be directly connected to the corresponding template of the frequency converter for processing, which is more suitable for this control system

the design wiring of the control board terminal of the powerflex700 vector converter is shown in Figure 2:

due to the use of fieldbus control, only some signals need to be input and output

4. Research on powerflex700 inverter in this system

in this system, the inverter adopts Rockwell AB series powerflex700 model, and its vector converter has the functions of v/f control, speed sensorless vector control and speed sensor vector control. It is suitable for heavy lifting mechanism, material handling and extrusion machine and mixer. According to the requirements of hardware wiring and vector control, the parameters of the frequency converter of the lifting device are optimized. The following is a brief introduction of some parameter settings in the system:

motor control parameters

p53=4, p88=1, p412=0 decide that the system is vector control, and use the force vector control technology of AB series frequency converter

p413=1024 is the encoder pulse frequency setting

p155, and p163 is the selection of frequency converter braking mode. Because the design braking power is far greater than the internal braking power, p163=1 is set here, and the external braking resistance is connected. After the lifting device stops, the frequency converter will stop output immediately, which will cause hook slipping in theory, so set p155=1, slope braking mode

p140 and p142 are the setting of acceleration and deceleration time. The setting of these two parameters determines the dynamic response time of the system, which will directly determine the rapidity of the vector variable frequency speed regulation system

ab series inverter has a fixed control word as the interface through field bus communication, but if you need to read the inverter parameter status, you need to use datalink to connect with the inverter

5. Idea of establishing control model

the biggest problem restricting the use of frequency converter on crown block is that the torque of frequency converter is small when starting, which makes it easy to slip hook when starting with heavy load. When controlling the sliding hook, the interlocking of the moment when the system reaches the sliding hook can be added to the starting condition of the system, so as to control the opening condition of the holding brake system, which can theoretically eliminate the possibility of sliding hook

according to the vector control schematic diagram of powerflex700 frequency converter, we can find that the final output torque current of the frequency converter determines the size of the lifting distance, and all external input parameters are variable. We are only willing to take some small equipment products for water test first

according to the torque characteristics of AC motor, when the motor is in vector control mode, if the motor is below the rated speed, the percentage of torque current and constant torque current is the percentage of output torque and rated torque. In this way, we can use the torque current output by the frequency converter as the only variable to control the slip hook. Through datalink method, the torque current of the frequency converter is collected into the ControlLogix framework, processed by 1756-l61cpu, and then the operation instruction of the frequency converter is given, so as to achieve the purpose of avoiding hook slipping

when the lifting frequency converter is started, the output speed, torque current and the actual return speed curve of the frequency converter can be in one quadrant. A vertical line is made at the lowest point of the actual speed, and the torque current value at the intersection with the torque current value is the current value required when the torque reaches

in the actual research process, the value can be obtained through the driveobserver of Rockwell's drivetools software

connect the corresponding parameters, monitor the utilization limit line of the waste foam granulator, and obtain the corresponding value

compare the data on torque current datalink with the empirical value of hook slipping, and string it into the holding brake control interlock. The control program interlock is shown in Figure 6:

6. Software programming design

this system is Rockwell controllfix integrated architecture, and the programming software is programmed with rslogix5000 software. According to the process requirements and good hardware foundation, the software design realizes reasonable interlock, comprehensive protection, simple program It is easy to read and write, convenient and fast to query and other effects. At the same time, it also realizes the smooth transmission of the interlocking signals of the lifting device, crane travel, trolley travel, and hydraulic lubrication system. It provides strong software support for the long-term stable operation of the vector frequency conversion system of the new 20+20 ton crown block

7. application effect evaluation

through the application of powerflex700 vector control frequency converter, the accurate positioning of the equipment is realized, the impact of the equipment is reduced, the stability of the main lifting is improved, the smooth lifting of thin gauge plates and long steel plates is realized, and the surface scratch of steel plates is effectively prevented. (end)

Copyright © 2011 JIN SHI