Siemens Sinamics G120P Operating Instructions Manual page 303

Switching-in a pump via PID
This application is used to operate several pumps connected in parallel depending on the
water demand.
One pump is controlled and monitored directly from the inverter, and the other pumps are
switched-on and off depending on the demand. Feedback from the other pumps is not
required. The monitoring is done using pressure sensors together with the PID closed-loop
controller. Cascade control is used, see Cascade control (Page 408).
The analog inputs are used to set the setpoint and to receive the feedback signals from the
various sensors, to which the PID closed-loop controller then responds. The digital outputs
are used to control the fans.
Because all pumps can be switched on and off by the inverter, the pumps can be used with
different frequencies. This ensures that no pump operates continually and the workload is
distributed equally among the pumps.
The system consists of the following components:
● Control Unit
● Power Module
● Motor
● Geared motor
● Pumps
● Pressure sensor
● Flow sensor
● Level sensor
● Motor temperature sensor (optional)
Boost
At low output frequencies, only a low output voltage is achieved using the V/f characteristic
control. This means that the output voltage can be too low to:
● Magnetize an induction motor
● Maintain the load
● Compensate for losses in the system
● Generate a tensioning, acceleration or braking torque
The boost function can be used to increase (boost) the output voltage of the inverter.
The "boost" wizard navigates you when setting the boost function.
Inverter cabinet units
Operating Instructions, 12/2014, A5E32923362A
Operation
6.10 Operation with the IOP
303