BENSHAW RSi H2 Series - Flow Compensation

PID Control
238
890053-00-02
6.3.5 Flow Compensation
In a system with a pipeline, longer pipes and higher flow rate cause greater pressure loss. A flow
compensation operation can compensate for pressure loss by increasing the value of the PID
reference.
Group
Code
Name
LCD Display
Parameter Setting
Setting Range
Unit
AP1
30
Flow Comp
function options
Flow Comp Sel
-
0
No
-
1
Yes
31
Max Comp
amount
Max Comp Value
-
0–Unit Band
-
Flow Compensation Setting Details
Code
Description
AP1-30
Flow Comp Sel
Sets the Flow Compensation function options.
AP1-31
Max Comp Value
Sets the maximum compensation amount. This function is based on a PID
operation. The amount is in the same units used for the PID reference.
Longer pipes cause the actual pressure to decrease which in turn increases the difference
between the pressure reference and the actual pressure. When comparing two systems of equal
pipe lengths, more pressure loss is caused in the system with greater flow. This explains the
pressure difference between (A) and (B) in the figure (when the flows are different). To
compensate for the pressure loss, the value of AP1-31 is set to the maximum amount of
compensation when the inverter has the maximum frequency and adds to the PID reference after
calculating compensation amount based on the output frequency.
The final PID reference=PID-11+Compensation amount. Compensation amount is shown below.