The signals from the DCS to the frequency converter fluctuate simultaneously
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Hello everyone, I’ve run into a strange problem recently; I’d appreciate it if you could help analyze it. 2 independent AO outputs to 2 frequency converters located in different places on site. The fault is characterized by intermittent occurrences (every one or two weeks) of a drop in the current of both frequency converters, along with a corresponding decrease in the pressure at the motor outlet. The DCS cards, terminal boards, and frequency converters have all been replaced. The fault has not been resolved. The shielding and grounding resistance of the signal lines are all normal. Other than that, the cable hasn’t been replaced. Thank you all first! Is there a solution?
Just try it with a temporary cable and you’ll know
Try using a temporary cable; if that doesn’t work, redo the configuration. If that still doesn’t solve the issue, then it’s necessary to check whether there are any other interferences, and whether the current level changes as well when something is altered Could there be any major sources of interference?
Is there a signal isolator between your DCS and the frequency converter?
Plan to add 2 and give it a try. I wonder if it will work or not.
The key is 2 independent circuits and 2 independent frequency converters. It’s strange when they occur at the same time.
OP, this is a interference issue! If there are no issues with the card components and cables (firstly, they must comply with design and installation specifications), then the problem of coupling interference between signals needs to be considered. Additionally, since the frequency converter is a device that converts AC to DC and then back to AC, it is theoretically possible for high-frequency voltage interference from the frequency converter to occur. Therefore, the following recommendations are given: 1. Add isolation between the DCS system and the frequency converter (use analog safety isolators for analog signals, and isolation relays for digital signals) ； 2. Make appropriate adjustments to the PID parameters of the control loop to prevent coupling phenomena.
Thank you, I plan to install a signal isolator.