Ramps; Proportional Differential Pressure, Parabolic - Grundfos CUE Series Product Manual

Functions

Ramps

The controller incorporates two types of ramp:
• ramp-up and ramp-down (default)
• initial and final ramps (setting via PC-Tool).
Speed
Nominal
Max.
Min.
Initial ramp
Ramp-up
Fig. 30 Ramp-up and ramp-down of the CUE
Ramp-up and ramp-down
The ramp-up and ramp-down are used for protection
against overload when starting and stopping the CUE.
The setting is done by means of the control panel.
The ramp-up time is the acceleration time from 0 rpm to
nominal motor speed.
The ramp-down time is the deceleration time from nom-
inal motor speed to 0 rpm.
Additional set of ramp-up and ramp-down (setting via
PC Tool)
An additional set of ramp-up and ramp-down can be
remote-set to predefined ramps by means of a digital
input.
Initial and final ramps
The initial and final ramps prevent operation for a
longer time than necessary at speeds below minimum
speed.
The setting is done automatically based on the pump
family selected in the start-up guide.
Proportional differential pressure,
parabolic
Setting via PC Tool.
The proportional differential pressure can be selected
with one of these flow dependencies:
• linear (default), see page 15
• parabolic (setting via PC Tool).
When the flow dependency is selected as parabolic, the
differential pressure of the pump will be reduced with a
parabolic curve at falling flow rate and increased at ris-
ing flow rate. See fig. 31.
Time
Final ramp
Ramp-down
The pump is controlled according to a differential pres-
sure measured across the pump. This means that the
pump system offers a flow-compensated differential
pressure in the Q-range of 0 to Q
the parabolic curve in the QH diagram.
Q
max.
Fig. 31 Proportional differential pressure, parabolic curve
Grundfos CUE
CUE
Δp
, represented by
max.
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