Rockwell Automation 21G PowerFlex 750-Series AC Drives Programming Manual - Manual (Page 470)

470 Rockwell Automation Publication 750-PM001J-EN-P - October 2014
Appendix B Application Notes
Pump Off Control Outlines
Automatic /Position Baseline Set
The following is a general outline of how the initial Pump Off control is
configured in the PowerFlex 753. This is the default configuration, using the
down stroke torque with P1187 [Pump Off Config] set to 0 “Automatic” or 1
“Position” and P1190 [Pump Off Control] set to 1 “Baseline Set.”
Set Base Speed Command
A commanded speed setting is chosen, based on well characteristics, that
produces desired pump performance most of the time. Pump off control is then
set up to maintain acceptable pump performance when conditions temporarily
change.
1. Pump off control requires the drive to be “At Speed.” Check P935 [Drive
Status 1] Bit 8 to verify this operating condition.
2. When P935 [Drive Status 1] Bit 8 “At Speed” = 1, the internal pump jack
at speed bit is set and the current speed command is saved.
3. The next ten down stroke torques are sampled and added together.
4. The average of the down stroke torques is saved as the baseline for the
current speed.
5. P1191 [Pump Off Status] Bit 6 “Pump Stable” = 1.
When Bit 6 = 0, the drive is averaging a new baseline torque.
6. The pump jack is running under normal conditions.
7. While running under normal conditions, every fifth stroke is compared
against the baseline to check for a pump off condition. The stroke count
can be monitored in test point TP 2043.
Change in Cycle Torque
If the cycle torque sample is less than or greater than the fixed setpoint by
the percentage set in P1195 [Pump Off Level], P1191 [Pump Off Status]
Bit 5 “PumpOff Alarm”= 1 and the drive waits for a second sample.
If the second sample is also less than or greater than the fixed setpoint by
the percentage set in P1195 [Pump Off Level], a Pump Off condition is
detected.
Run At Reduced Speed
When a Pump Off condition exists, and P1189 [Pump Off Action] is set
to 0 “Change Speed,” the percentage set in P1196 [Pump Off Speed]
lowers the commanded speed.
Reduced Speed = Commanded Speed - (Commanded Speed x P1196)