2-120 Process PI Loop
The option to invert the sign of PI Error is selected in the PI
Configuration parameter.
• Preload Integrator - This feature allows the PI Output to be stepped
to a preload value for better dynamic response when the PI Output is
enabled. Refer to diagram 2 below.
If PI is not enabled the PI Integrator may be initialized to the PI
Pre-load Value or the current value of the commanded speed. The
operation of Preload is selected in the PI Configuration parameter.
By default, Pre-load Command is off and the PI Load Value is zero,
causing a zero to be loaded into the integrator when the PI is disabled.
As below shown on the left, when the PI is enabled the PI output will
start from zero and regulate to the required level. When PI is enabled
with PI Load Value is set to a non-zero value the output begins with a
step as shown below on the right. This may result in the PI reaching
steady state sooner, however if the step is too large the drive may go
into current limit which will extend the acceleration.
PI_Config
.Invert
-
PI_Config
.Sqrt
PI Error
PI Fbk
+
–
PI Ref Sel
PI Fdbk Sel
PI_Config
.PreloadCmd
PI_Status
.Enabled
Preload Value PI Integrator
Spd Cmd
PI Enabled
Spd Cmd
PI Output
PI Pre-load Value
PI Pre-load Value = 0 PI Pre-load Value > 0
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