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Hello,
I am seeking some advice on a level control loop on site.
The loop controls a tank level by driving the output of a VF drive. It is very slow reacting as the link is via telemetry and the water is pumped about 10km.
The problem is the drive continuously ramps up and down, cycling even when the PV is far from SP. For example, when the tank is at less than 50% the output on the drive will fluctuate from 50% to 100%, stay there for a short while and then repeat. I would have thought being that far from SP the output should be locked onto 100% until it approaches SP.
I have tried a wide variety of PID settings in the control block in the PLC but nothing seems to change it.
Any advice on starting PID values for slow level loops?
The modicon PLC we have uses Proportional Band, Min/Repeat and Min time constant.
Cheers.
I am seeking some advice on a level control loop on site.
The loop controls a tank level by driving the output of a VF drive. It is very slow reacting as the link is via telemetry and the water is pumped about 10km.
The problem is the drive continuously ramps up and down, cycling even when the PV is far from SP. For example, when the tank is at less than 50% the output on the drive will fluctuate from 50% to 100%, stay there for a short while and then repeat. I would have thought being that far from SP the output should be locked onto 100% until it approaches SP.
I have tried a wide variety of PID settings in the control block in the PLC but nothing seems to change it.
Any advice on starting PID values for slow level loops?
The modicon PLC we have uses Proportional Band, Min/Repeat and Min time constant.
Cheers.