ABB ACS560 Firmware Manual page 135

Example of a 3-pump constant pressure water supply application:
Pump 1 is connected to Motor 1
Pump 2 is connected to Motor 2
Pump 3 is connected to Motor 3
Flow consumption versus pump status
Consumption
Low
↓
High
↓
Low
↓
High
↓
Low
↓
High
VSD
DOL
Off
Pump 1
VSD
DOL
DOL
DOL
Off
VSD
DOL
DOL
Off
VSD
DOL
Variable Speed Drive (yellow colour connecting line in the figure).
Controlled by drive, tuning the output speed according to PID control.
Direct On Line (red colour connecting line in the figure). Pump is running
at fixed motor nominal speed.
Off-line. Pump stops.
Pump 2
Off
VSD
DOL
Off
Off
Off
VSD
VSD
VSD
DOL
DOL
Control macros 135
Pump 3
Off
Off
DOL
VSD
Off
DOL
DOL
Off
Off
Off
VSD