130 Control macros
pump one by one, but the auxiliary motor is always is on-line in DOL mode.
Two pumps meet the flow consumption for long term running and the 3rd pump is
reserved for shifting. All the motors shifts for autochange routine and special
auxiliary circuit is needed for the same. This system is similar to the SPFC.
Example of PFC autochange with all motors in a 3-pump constant pressure water
supply application:
Pump 1 - connected to Motor 1
Pump 2 - connected to Motor 2
Pump 3 - connected to Motor 23
Flow consumption versus pump status
Consumption Pump 1 Pump 2 Pump 3
Low VSD Off Off
Normal VSD DOL Off
↓ Off VSD DOL
↓ DOL Off VSD
Normal VSD DOL Off
VSD Variable Speed Drive (yellow colour connecting line in the figure).
Controlled by drive, tuning the output speed according to PID control.
DOL Direct On Line (red colour connecting line in the figure). Pump is running
at fixed motor nominal speed.
Off Off-line. Pump stops.
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