Rockwell Automation 1395 DC Drive, 800-1250 Hp, FRN 5.XX-9.30 - Manual (Page 54)

Chapter 3
Functional Description
3-21
been provided. Desired Contour (Parameter 653), specifies the rounding of
the edges of the velocity profile or “S” filtering. These functions can be
bypassed by setting bit 5 in Logic Command.
Ramp Velocity Reference (Parameter 103), is the output of the Ramp and
Contour function blocks. The value of this parameter is conditionally
offset by the Droop function (if used), to become the Final Velocity
Reference (Parameter 104). The output of the Droop Control (Circle 6) is
derived from Torque Command (Parameter 110), along with Droop Percent
(Parameter 657) and Droop Gain (Parameter 658). Ramp Velocity
Reference (Parameter 103), is the output of the Ramp and Contour function
blocks. The value contained in this parameter is conditionally offset by the
Droop and Process Trim functions (if used), to become the Final Velocity
Reference, (Parameter 104). The output of the Droop Control (Circle 6) is
derived from Torque Command (Parameter 110), along with Droop
Percent, (Parameter 657) and Droop Gain, (Parameter 658). The Process
Trim Control (Circle 4) allows either the speed reference or torque
reference to be trimmed according to the process. It contains its own PI
Control block, along with filters and limiting functions. A selection block
in logic, controlled by Process Trim Select (Parameter 628), sends the
output to be summed with the input to the velocity loop, or summed with
External Torque Reference (Parameter 157), to be used as a torque
reference.
Velocity Feedback Control (Circle 4)
The 1395 allows different methods of motor speed feedback. A digital
encoder, analog DC tachometer or armature voltage may be selected as
feedback methods. Feedback Device Type (Parameter 621), selects the
source for motor velocity feedback. Velocity Filter Select (Parameter 631)
provides the option of using a filter and designating what type it will be.
The output of the Feedback Filter block provides the Velocity Feedback
(Parameter 106). The “No Feedback” option is typically used for drives
operating as torque regulators (torque mode select).
Velocity Pl Control (Circle 5)
Compares the speed reference value from the Velocity Reference Control
to the actual motor speed, from the Velocity Feedback Control. The Final
Velocity Reference (Parameter 104), is modified by KF Velocity
(Parameter 661). This parameter controls the amount of velocity reference
that will be summed with velocity feedback. This is filtered and modified
through a Proportional/Integral (PI) Control function. The proportional
gain of the PI Control is determined by the value of KP Velocity Loop
(Parameter 660). A value of 8 in Parameter 660 will provide a gain of 1.
The integral gain of the PI Control is determined by the value of KI
Velocity Loop (Parameter 659). The output of the velocity control
firmware is a torque reference, which is limited before being applied to the
torque selection block.