In the distributed control system DCS, the main control network sometimes uses the MODBUS protocol, and the remote field device uses the PRIFBUS-DP protocol. At this time, the signals of the field devices need to be transmitted to the main control network for monitoring and control, thereby implementing two different protocol networks. Communication. This case is such a situation. In the central air-conditioning compressor motor control system of a building in Fujian, Emerson EC20 series PLC (MODBUS master station) needs to monitor the site of the Danfoss VLT6000 series inverter. The Danfoss VLT 6000 uses the PROFIBUS-DP protocol to control the lower motor. This requires the use of a module that converts from PROFIBUS to MODBUS protocol. The DME master gateway PBM-G-MBS provides a solution.
1. Hardware selection of automatic control system Because of the need to convert from PROFIBUS to MODBUS protocol, then a module is needed. It can be used as a PROFIBUS master station and can also be connected to a MODBUS network. This is the master station of Dingshi. Gateway PB-G-MBS function.
2. General control requirements and functions In the central air-conditioning compressor motor control system of the building, an Emerson EC20 PLC is required to acquire the control signals in the Danfoss VLT 6000 inverter, such as temperature, pressure, etc., and then control the inverter through these signals. Finally, the linkage motor realizes the control of the on-site Freon compressor and finally realizes the temperature control of the entire building.
3. System Configuration and Layout In this system, Emerson EC20 PLC collects the data of 2 VLT6000s on the ground floor and 13 VLT6000s on the ninth floor of the ground. The communication data volume is about 180 bytes. Its automatic control system is shown in the figure below.
4, system software Dingshi master gateway PBM-G-MBS configuration software for PBconfig. The VLT6000 drive used in this case needs to be configured here. The following is the configuration process:
(1) Put the GSD file corresponding to the VLT6000 into the GSD directory and update it.
(2) Set serial port parameters. This parameter is used for MODBUS side communication.
(3) In the classification column on the right, find the device to configure.
(4) After the configuration, click Compile and Download to download the configuration information to the master gateway.
(5) Finally, the communication data can be observed in the address mapping table.
5. Conclusion In this case, we provided a solution for PROFIBUS slave station to MODBUS master station communication. In the past, such on-site requirements were basically impossible to implement. Even if they could be realized, they would need to go through a more complicated networking process. The cost was greatly increased, and the system stability was poor, which was not conducive to maintenance. Through the master station gateway PBM-G-MBS, not only provides a simple solution, but also greatly reduces the project cost, and is easy to maintain, greatly improving system stability.