PID control problem
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Control of alkali pump: The Danfoss VLT2800 under CPU315-DP uses PID to automatically control the PH value on WINCC. Now the PH is set at 8, but the VLT2800 frequency does not change when it rises to 30.6. At this time, the PH value is around 7.4 and has not been reached. The frequency limit of the inverter is 50HZ. I don’t know why? I also tried adjusting the setting value below 7.4, but the frequency will drop! What are the common causes of such failures?
It is recommended to do PID control in step 7, do not use the upper level to do it, it is unsafe. From your phenomenon, it may be that the VLT2800 has an upper limit, or the speed of the frequency conversion is too fast and there is protection.
This was done in STEP7. The upper limit of VLT has been set to 50HZ. As for the possibility of protection due to too fast frequency conversion speed, I have not considered it. My acceleration time is set at 3S, which may be too fast.
First try to manually output 0-100%. Is the inverter changing normally? Then take a look at the input and output range of the regulator, right? Look at the settings of the inverter again. This post was last edited by zhaohh3211 on 2009-3-16 09:35 ]
Should we check the PID parameter settings? It seems that the reason is that the PID setting is unreasonable, resulting in too big a difference?
PID is usually done by the lower computer and rarely by the upper computer.~
I feel that there is something wrong with your inverter parameter settings. Different working modes of the inverter may have several parameters to limit its speed. I suggest you familiarize yourself with the mutual constraints of the inverter parameters and see if you can solve it.
It is indeed a problem with the inverter parameter setting. Parameter 205 is the most* * The value is limited to 30.5. This problem has been solved. Thank you!