Application of the hottest frequency converter in

2022-08-23
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Application of frequency converter in medium and heavy plate finishing system

the system uses Siemens S7-300PLC to realize frequency converter network control through PROFIBUS-DP bus, so as to realize the a-automation production of medium and heavy plate finishing system. System debugging, convenient maintenance and reliable operation

in recent years, with the rapid growth of decentralized structure in production automation and process automation, the application of fieldbus system has become increasingly common. One of the reasons is that the fieldbus system realizes the data transmission between digital and analog input/output modules, intelligent signal devices, process regulation devices, programmable logic controllers (PLC) and PCs, dispersing the I/O channels near the actual field equipment, minimizing the cost of installation and wiring, thus greatly saving the cost. The second reason is that the standardized fieldbus has an "open" communication connection i:1, which allows users to choose decentralized I/O devices and field devices produced by different manufacturers. At the same time, it can also easily realize the connection of secondary and tertiary networks. Due to the large number of equipment in the finishing area of Jigang medium and heavy plate phase III project and the dispersion in a large range, it is particularly suitable to use fieldbus to realize the automatic control of the production process

system introduction

the main equipment in the plate finishing area includes: cooling bed input roller table, input lifting chain, roller plate, output lifting chain and output roller table, lubrication station and cooling fan of cooling bed, as well as flame cutting system, transportation roller table, turnover machine, electromagnetic crane, etc. Most of the original automation equipment of the plate plant adopts the products of Siemens company. In order to facilitate maintenance and network connection, the automatic control equipment in the finishing area is also mainly Siemens products, and the PLC is S7-300, of which the CPU model is 315-2dp. The drive system is all simovertmasterdrivers vector controlled frequency converters

at the same time, in the PROFIBUS-DP system of l# cooling bed and finishing area, 2# station S7-300 is the main station, and the modules of this station are the input and output points of the cooling bed system

3 sample stations, 17 sample stations are remote et-200, of which 3 sample stations et-200 is the remote I/O of the finishing system, and 17 sample stations et-200 is the remote I/O of the cold bed operation console. Station 4 ~ 8 # is the input-output system drive frequency converter, station 9 ~ 16 # is the 1 # cooling bed system drive frequency converter, and station 18 ~ 2L is the 2-sample cooling bed system drive frequency converter

bus connection

profibus-dp system is a linear bus structure with active terminators at both ends, also known as RS485 bus section. At most 32 stations can be connected on a bus section. 9-pin D-type connector is used for the interconnection between bus station and bus

the socket of type D connector is connected to the bus station, and the plug of type D connector is connected to the bus cable

every station connected to the bus, whether master or slave, behaves as an RS485 current load. The active bus terminal is connected with a terminal resistance to prevent reflection during data transmission, and when there is no station activity on the bus, it ensures that there is a certain idle state potential on the data line. In this system, there are 20 stations on a bus section. Two sample stations and one sample station are connected to the two terminals of the bus, and the terminal resistance can be converted between connection and disconnection by the switch located in the neutral plug

The prohbus-dp protocol is designed for high-speed data communication required by decentralized I/O and field devices in automated manufacturing plants. The typical DP configuration is a single master station structure. The communication between the DP master station and the DP slave station is based on the master-slave principle, that is, only when the master station requests, the DP slave station on the bus can be active

dp slave station is accessed by DP master station according to the polling table. The user data between DP master station and DP slave station is continuously exchanged without considering the content of user data. This typical structure is used in the plate 1# cooling bed and finishing area, as shown in Figure 1

setting of frequency converter

(1) the communication between frequency converter and master station S7-300 is realized by installing CBP communication board on simovertmasterdrivers.

cabinet mounted frequency converter has 6 slots for installing optional boards, and CBP communication board can be installed in any slot. After the communication board is installed, it can be started for configuration. First, the station address must be determined, which is completed through the parameter setting of the frequency converter. The process is shown in Figure 2. The CBP communication board has three indicator lights to display the communication status. The three indicators are: red is the running light; Yellow is the light for data exchange with the frequency converter; Green is the light for data transmission with profibusdp. Only when these three indicators flash at the same time, the system communication is normal

(2) PROFIBUS-DP data is exchanged in the form of messages

the data transmitted by each message can be divided into two groups, which need to be set during hardware configuration with STEP7. These two sets of data are parameter PKW and process data PZD respectively. The PKW data segment is used to read and write the parameter values of the frequency converter and all the characteristics of the read parameters. The PZD data segment transmits the control information of the frequency converter, that is, the control parameters of the frequency converter. The S7-300 of the master station sends the control word and set point to the frequency converter, and the frequency converter returns the status word and actual value. The data length of PKW and PZD can be set as required, and the data transmission rate can be set at the same time. In this system, PKW and PZD are set to 4 words and 2 words respectively, and the baud rate of communication data transmission is 1.5mbit/s

(3) functional features of inverter communication product: setting of signal control parameters

the basic process of inverter parameter setting is as follows: after the inverter is powered on, first restore the parameters to the factory settings, then carry out C to stop the configuration of BP board for tensile, shear and compression tests of samples, select p060=5 for system setting, and finally set the connection between control word and status word, Connect the vector control switching value and vector control connection value with the parameter value and control word defined in PLC. The main connection parameters of this system are shown in the attached table

(4) due to the relatively accurate positioning of the turnover machine, roller table and other equipment, and the fast production pace, each transmission frequency converter has an external braking unit and braking resistance

the braking unit is connected to the frequency converter through the intermediate circuit. When the intermediate circuit voltage reaches the predetermined value, the braking unit is automatically connected to prevent the intermediate voltage from rising. Parameters related to braking: p462 refers to the time from static acceleration to reference frequency; P463 is the unit of acceleration time; P464 is the time from deceleration of reference frequency to standing; P465 is the unit of deceleration time. According to different process requirements, each frequency converter is set with different acceleration and deceleration time

electromagnetic interference of PROFIBUS-DP

the standard method of installing PROFIBUS-DP is: there is a ground reference potential, that is, all module racks and load current circuits must be connected to the common reference potential (ground), so as to ensure that the interference current caused by unreasonable PROFIBUS-DP cable laying or improper equipment installation can be shunted as soon as possible. When using this installation method, connect the grounding of each component (S7-300, et200, simovertmasterdrivers) to the common grounding point of the control cabinet. In this way, the bus plug connector connects the shield of pr0f1bus-dp cable with all bus stations in the network, and the interference current is shunted through the connected ground wire, thus preventing the fault caused by interference

because the transmission system requires large electrical power, power cables often transmit high voltage and current. If this kind of cable is laid in parallel with PROFIBUS-DP cable for a long distance, capacitive and inductive interference will be generated on the PROFIBUS-DP cable, thus disturbing the data communication in the network. To avoid this interference, when laying PROFIBUS-DP cable, ensure the distance between PROFIBUS-DP cable and other wires and cables. During construction, 5. The calculation formula often used in random vibration experiments should lay power cables and PROFIBUS cables on isolated cable trays as far as possible

after the system is put into use, it has achieved good results:

1) the system is stable and reliable, and the maintenance and overhaul workload is less

2) the variable frequency drive system has fast response speed and accurate and reliable positioning

3) it can be easily connected with the secondary system to lay the foundation for the automation of the whole line

4) guaranteed the product quality and achieved good economic benefits

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