Pid Controller - Grundfos CUE Series Product Manual

Functions

PID controller

The CUE has a built-in PID controller for speed control
of pumps. The factory setting of gain (K
time (T ) can easily be changed in the control panel.
i
The controller can operate in both normal and inverse
mode.
Normal mode
Normal mode is used in systems in which an increase
in pump performance will result in a rise in the value
measured at the feedback sensor. This will typically be
the case in most CUE applications.
Normal mode is selected by setting the gain (K
positive value in the control panel.
Inverse mode
Inverse mode is used in systems in which an increase
in pump performance will result in a drop in the value
measured at the feedback sensor. This mode will typi-
cally be used for constant level operation (emptying
tank) and for constant temperature operation in cooling
systems.
Inverse mode is selected by setting the gain (K
negative value in the control panel.
Description
The PID controller compares the required setpoint
(p ) with the actual value (p) measured by the trans-
set
mitter (P). See fig. 21.
Setpoint p
set
CUE
p
set
Q
Fig. 21 Constant pressure control
If the measured value is higher than the required set-
point, the PID controller will reduce the speed and the
performance of the pump until the measured value is
equal to the required setpoint.
) and integral
p
) to a
p
) to a
p
Measured value p
P
Q
max
Suggested controller settings
System/application
Heating
system
CUE
p
SP, SP-G, SP-NE: 0.5
CUE
p
SP, SP-G, SP-NE: 0.5
CUE
Q
CUE
L
CUE
0.5
t
L
2
CUE
Δt
L
2
t
CUE
L
2
0.5
CUE
Δp
CUE
L
1
Δp
*Ti = 100 seconds (factory setting).
Heating systems are systems in which an increase in pump performance
will result in a rise in temperature at the sensor.
Cooling systems are systems in which an increase in pump performance
will result in a drop in temperature at the sensor.
L =Distance in [m] between pump and sensor.
1
L =Distance in [m] between heat exchanger and sensor.
2
Grundfos CUE
K
p
T
Cooling
i
1) 2)
system
0.2 0.5
0.5
0.2 0.5
0.5
0.2 0.5
–2.5 100
10 + 5L
–0.5
2
10 + 5L
0.5
2
30 + 5L *
–0.5
2
0.5 0.5*
L < 5 m: 0.5*
1
L > 5 m: 3*
0.5
1
L > 10 m: 5*
1
21