Application note AN-ODV-2-068
22 October 2014
AN-ODV-2-068 Using Optiflow Multi Pump Cascade Control
4
For consistent operation, of the system, P2-27 should be equal to or greater than the Pump Settling Time, P8-19. This ensures
that Standby Mode is not activated during cascading of the Assist Pumps.
The PID Error Wake Up Level, P3-13 is entered as a % of the transducer range.
For example, in a closed loop pressure control system with a pressure transducer providing feedback, if a 0 – 10 bar feedback
transducer is used, and the system is intended to operate at 4 bar working, it may be desired to switch the drive to Standby
Mode, and only restart when the system pressure falls below 3.8 Bar. The PID Wake Up Error Level can then be calculated as
(4.0 – 3.8) / Transducer Range = 2.0%
Note : In order for Standby Mode to activate, the Output frequency must remain below the threshold set in P3-14 for the time
set in P2-27. This requires the PID settings of the Master drive to be tuned correctly to ensure that the output frequency
continues to drop when the system setpoint is held and no flow demand exists.
When Standby Mode is activated on the Master drive, the output of the PID controller will be set to zero. When the PID Error
Wake up level exceeds the programmed threshold, the
PID Controller
will restart
. The drive will not recover from Standby until
the output of the PID Controller exceeds the Standby Activation Speed
. For this reason, it is advisable to limit the minimum
output of the PID Controller, based on the chosen Standby Mode Activation Speed.
PID Low Output Limit, P3-08 = (P3-14 / P1-01)% – 1.0%
E.g. In the example above, where maximum speed = 1500 Rpm, Standby Activation Speed = 1250 Rpm
P3-08 = (1250 / 1500)% - 1.0% = 82.3%
This setting ensures a rapid recovery from Standby Mode when required.
Appendix:
Revision History
Issue
Comments
Author
Date
01
Document Creation
KB
24/04/13
02
Updated to new format
KB
28/04/14
03
Corrected error on parameter number
KB
22/10/14