PCP/ESP program features 47
Shutdown procedure
There are two ways to stop the drive: by coast stop or backspin control. If Backspin
control is disabled, then the drive performs normal coast stop.
Pump backspin control
Pump backspin control protects the pump during shutdown process. Backspin control
may be performed by two different function: backspin function and start delay
function.
Backspin function eliminates the effect of uncontrollable rotation of the pump in
opposite direction, that is caused by the back flow of fluid. Backspin function allows to
keep this reverse rotation below the defined speed limit. This sequence can be
performed with any stop command. User can enable this function using parameter
80.01 Backspin enable.
When zero speed is reached, the drive begins ramping to the backspin speed
reference with an acceleration time in parameter 80.03 Backspin acc time. If the
torque in the pump is driving the motor in the reverse direction, then the actual
backspin speed is equal to the backspin speed reference. If torque in the pump is not
driving the motor in reverse, the actual speed is not equal to backspin speed
reference.
Backspin speed reference is based on actual torque.
As torque decreases, backspin speed reference increases. If torque is constant,
backspin speed range increases with the decrease in backspin speed reference.
The following procedure and time scheme describes the operation of backspin
function:
1. The Drive receives an external stop command and starts to decelerate the pump
down along the defined ramp (74.11 Rod dec time).
2. At zero speed, the fluid starts flowing back from the pipe. The function keeps the
drive operational (delaying the internal stop command).
3. Backward flow accelerates the pump in reverse direction. The Backspin function
keeps the acceleration rate under the acceleration level (80.03 Backspin acc
time).
4. The Backspin function keeps the reverse speed under the Backspin speed limit
(80.05 Backspin speed range trim) until the back flow starts running out and the
torque starts decreasing.
5. When the actual torque goes below the limit (80.04 Backspin stop torque), the
function stops and initiates the Coast to stop command to the drive.
Backspin Speed Ref
= Backspin Limit -
Max Torque
* Backspin Limit *Backspin Speed Range
Actual Torque Filtered
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