Application examples
Pressure control
13−1
L EDB82MV752 EN 5.2
13 Application examples
13.1 Pressure control
A centrifugal pump (quadratic load characteristic) is to maintain constant pressure in a pipeline
system (e.g. water supply for private households or industrial plants).
Basic conditions
PLC operation (selection of the pressure setpoint, night−time pressure reduction).
On−site set−up is possible.
During the night the pressure is reduced, and the pump then operates at an unregulated, low
constant speed.
Under no operating circumstances must the pump be operated at an output frequency of less
than 10 Hz (dry running).
Avoidance of pressure surges in the water network.
Avoidance of mechanical resonance at an output frequency of approx. 30 Hz.
Overtemperature protection for the motor.
Collective fault messaging to the PLC.
On−site display of readiness for operation and the actual pressure value.
On−site facility for stopping the pump.
Functions used
Internal process controller for pressure control
– Pressure setpoint from the PLC (4 ... 20 mA)
– Actual pressure value from the sensor (0 ... 10 V)
Manual/remote switchover for on−site set−up
– Manual: Pressure setpoint entered via a pushbutton with motor potentiometer function
(UP/DOWN)
– Remote: Pressure setpoint from the PLC
Fixed speed (JOG) for night−time pressure reduction (activated via the PLC).
Protection against dry running (setpoint−independent minimum speed).
Smooth and jerk−free starting action with S−ramps.
Masking of mechanical resonances with a cancelling frequency.
PTC motor monitoring.
TRIP error message via a digital output.
Readiness for operation via a relay output.
Configurable analog outputs for actual pressure value.
Electric device lock (CINH).
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