Rockwell Automation 20G PowerFlex 750-Series AC Drives User Manual
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Rockwell Automation Publication 750-RM002B-EN-P - September 2013
Chapter 4
Motor Control
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“Int Ramp Ref ” (1) – Inertia compensation is enabled. The function is
configured to use the rate of change of P595 [Filtered Spd Ref ]. This is the
typical setting that should be used for inertia compensation on a stand-
alone drive.
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“Ext Ramp Ref ” (2) – Inertia compensation is enabled. The function is
configured to use the rate of change of P700 [Ext Ramped Ref ]. This
setting is available for applications that supply a ramped speed reference
external to the drive.
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“Spd Rate Ref ” (3) – Inertia compensation is enabled. The function is
configured to use the P596 [Speed Rate Ref ]. This parameter should
contain a value that represents the rate of change of the motor speed
reference. This setting is available for applications that supply a ramped
speed reference external to the drive.
Parameter 76 [Total Inertia] is calculated during the autotune and is used along
with the calculated acceleration or deceleration rate to calculate the torque adder.
Parameter 696 [Inertia Acc Gain] determines the gain for the inertia
compensation during acceleration. A gain of 1 results in 100% compensation.
Parameter 697 [Inertia Dec Gain] determines the gain for the inertia
compensation during deceleration. A gain of 1 results in 100% compensation.
Parameter 698 [Inertia Comp LPFBW] Inertia Compensation Low Pass Filter
Bandwidth. Sets the bandwidth of a low pass filter for the inertia compensation
function. The output of this filter supplies P699.
Parameter 699 [Inertia Comp Out] Inertia Compensation Output. Displays the
output of the inertia compensation function.
Parameter 700 [Ext Ramped Ref ] External Ramped Reference. This parameter is
meant for an external motor speed ramp input signal. This signal will be used by
the inertia compensation function when P695 [Inertia CompMode] = 2 “Ext
Ramp Ref.” This parameter will be entered in units of Hz or RPM, depending on
the value of P300 [Speed Units].
Parameter 596 [Speed Rate Ref ] Speed Rate Reference. This parameter is shared
by both the Inertia Compensation and Speed Compensation functions.
A value shared by both the Inertia Compensation and Speed Compensation
functions (active only in FV motor control modes), typically supplied by an
external controller that is also providing a rate limited speed reference. The Speed
Rate Reference corresponds to the derivative with respect to time of the speed
reference signal. Units of time are in seconds.
For example, if the controller provides a 10 second reference ramp, the controller
would also supply a Speed Rate Ref value of 1 pu / 10 sec = 0.1 sec-1 while the
reference is accelerating. When the reference is constant, Speed Rate Ref should
be zero.
For additional illustration of the control refer to PF755 Control Block Diagrams
in the PowerFlex 750-Series Programming Manual, publication
.