Evoqua WALLACE & TIERNAN MFC, Instruction Manual

Page: 84 / 268

84
WT.050.580.000.DE.IM.0714
Functions
MFC
4.
Special Functions • The control direction can be switched.
• Automatic determination of the control parameter using the
integrated fuzzy module. The fuzzy module determines the
control parameter from the embedded Tconst and Tvar
process times.
• The setpoint can be switched between internal and external
• Ypi stop function during a change in control variable
• Control variable Wq available optionally as proportional or
indirect proportional as well as factor adjustment
• Smooth switch from compound-loop-control to single feed
forward control or single feed back control via digital input 1, 2
or 3 available
Yout = Wq x (DF
Wq
+ ek x Kp x (1 + t/tn)) x Yout-factor
Ratio Feedback
control
t Internal controller cycle time
tn Integral action time
Kp Control amplification 100 / Xp
ek Setpoint-actual value control deviation
DF
Wq
Learned dosing factor for the current flow rate
Wq Flow rate signal in %
Yout Determined controller output value %
Yout factor This factor offers the option to increase the dosing
output if the setpoint is not reached with a dosing
factor DF of 100 %.
Setting range: 1.0– 4.0
Factory setting: 1.0
Determining combi-
control process times
To adjust the control for compound-loop-control, the Tconst and
Tvar process times must bet entered in the parameter menu path.
These times refer to control loop dead times,which on the one
hand are independent of the control variables, and on the other
hand depend proportionally on the control variables.
The constant dead time< Tconst > (independent of control
variable) consists of the control variable measurement dead time
(measuring dead time) and possible dosing delays.
The variable dead time< Tvar > depends on the current control
variable and is entered in the menu at a control variable of 100%.
The following calculation examples apply for the use of the MFC
for flow-controlled chlorine dosing with chlorine overfeed
correction (potable water control loop).
Note:
If this factor is increased, there is a danger that the
setpoint value will also not be reached with a higher
flow rate value, because the Yout value takes the value
100 % prematurely.