Lenze 8200 motec frequency inverter 0.25kW-7.5kW - Manual (Page 186)

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).