Rockwell Automation 1395 Digital DC Drive FRN 5-10.10/9.30 - Manual (Page 112)

Chapter 5
Functional Description
5-26
The selected speed reference then enters a speed limit block. The
maximum and minimum limit of the speed reference are adjustable by
changing the values of Forward Speed Limit (Parameter 608) and Reverse
Speed Limit (Parameter 607). Forward Speed Limit sets the maximum
speed reference for the forward direction, and Reverse Speed Limit sets the
maximum speed reference for the reverse direction.
Pre–Ramp Velocity Reference (Parameter 102) indicates the value of the
velocity reference that has been currently selected by the Velocity
Reference Control. Parameter 102 is also the input to the Ramp Control.
Two parameters control the accel and decel rates of the Ramp function.
Accel Time, (Parameter 651), defines the time in seconds for the output of
the Ramp to go from zero to base speed (linear beyond base speed). This
rate applies to both forward and reverse speed references. Decel Time
(Parameter 652), defines the time in seconds for the output of the Ramp to
go from base speed to zero speed reference in both the forward and reverse
directions. In addition to the Ramp function, an “S” filter function has
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).