Rockwell Automation Publication 750-PM001N-EN-P - February 2017 467
Application Notes Appendix C
8. When the reduced speed is reached, P935 [Drive Status 1] Bit 8 “At
Speed” = 1, the next ten down stroke torques are sampled and summed.
9. The average of the down stroke torques is saved as the baseline for the new
speed. P1191 [Pump Off Status] Bit 6 “Pump Stable” is reset.
10. The pump jack runs at the reduced speed for the length of time set in
P1197 [Pump Off Time] then the pump jack resumes pumping at the base
speed command. (Step 6
in this sequence.)
If P1189 [Pump Off Action] is set to 3 “Stop After 2,” go to Step 11
.
Whenever the operator changes the base speed command, the process
starts over at Step 1
in this sequence. This action does not apply to speed
changes that are triggered by P1189 [Pump Off Action] when a pump off
condition is detected.
11. While running at the first reduced Pump Off Speed, every fifth stroke is
compared to the new baseline for a pump off condition.
If the down-stroke torque samples remain stable during the time set in
P1197 [Pump Off Time], the following occurs:
• Commanded speed returns to the original base speed
• Down stroke torque samples are compared against the original baseline.
(Step 6
in this sequence.)
If two down stroke torque samples are less than or greater than the new
baseline by the percentage set in P1195 [Pump Off Level], the following
occurs:
• The Pump Off condition persists
• The percentage set in P1196 [Pump Off Speed] lowers the commanded
speed a second time.
12. When the second reduced speed is reached, P935 [Drive Status 1] Bit 8
“At Speed” = 1, the next ten down stroke torques are sampled and
summed.
13. The average of the down stroke torques is saved as the baseline for the
second new speed. P1191 [Pump Off Status] Bit 6 “Pump Stable” is reset.
14. The pump jack runs at the second reduced speed for the length of time set
in P1197 [Pump Off Time] and resumes pumping at the base speed
command. (Step 6
in this sequence.)
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