Is it better to use a variable-frequency pump for regulation, or a mains-frequency pump with a control valve?
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Recently we have been discussing whether it is better to control flow rate and tank level using variable-frequency pumps, or by using conventional frequency pumps along with control valves The original design called for using a variable-frequency pump to carry out PID control; however, it has been suggested that a fixed-frequency pump combined with an automatic control valve is a better option for regulating flow or level, as the variable-frequency pump is not effective for this purpose. It is said that although variable-frequency pumps save electricity, their response speed to adjustments is slow. I would like to ask the experts: which is better, using a variable-frequency pump for regulation, or a normal-frequency pump combined with a control valve?
This depends on the actual operating conditions; there is no absolute answer as to which one is better. For example, in cases where the pump outlet has only one pipeline with no other branches and rapid speed adjustment is not required, using variable frequency control offers better economic benefits. For example, when there are multiple branches at the pump outlet and all of them need to be controlled, a combination of variable frequency voltage stabilization and control valves for flow regulation yields better control results. It depends on the specific manufacturing process.
It depends on the control requirements, which are specifically two factors: 1. Residence time, for example, 5 minutes. 2. The allowable range of liquid level variation, for example 10%. The shorter the residence time, the smaller the allowable variations, which requires more sensitive control; conversely, it becomes more difficult to control, in which case FV control is more appropriate. Generally speaking, the tolerance for L control parameters is high, so using variable frequency may be appropriate ； The tolerance for F/T control parameters is low, so careful analysis is required when using variable frequency.
What does FV mean, and what is L?