HMI and PLC communication failure - Database & Sql Blog Articles

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The two hmis used in our factory use DP communication with one S7-300. Now some devices will automatically stop, while others are running normally, and the devices are basically the same every time, as long as each After the communication indication on the secondary HMI interface suddenly turns red (sometimes the HMI turns red on the 1st, and sometimes the HMI turns red on the 2nd), it will be followed immediately, and then restarted. I have done a CPU diagnosis, and I have a sudden interruption of the inverter at station 9 (about 1S).
A: This problem is caused by electromagnetic interference generated by the inverter. It is recommended that:
1. The power line and signal line should be routed separately, and the metal hose should be well grounded. And install a reactor in the power supply.
2. The RS485 communication port must be connected to the host computer by optically isolated transmission to improve the anti-interference performance of the communication system.
3. The power supply of the external computer, HMI or instrument and instrument should be separated from the power supply of the inverter. Try to avoid sharing an internal transformer.
4. Install an inductive magnetic loop filter on the input or output of the inverter.
5. The E end of the inverter should be connected to the control cabinet and the outer casing of the motor. To be connected to the security ground, the grounding resistance should be less than 100Ω, which can absorb the surge interference.
6. Independent shielding should also be carried out on the disturbed instrumentation. The thermometers, PID regulators, plc, sensors or transmitters on the market must be equipped with a metal shielded enclosure and connected to the security ground. If necessary, the above-mentioned inductive magnetic loop filter can be added to the power incoming end of such a meter.