Rockwell Automation 1395 DC Drive, 800-1250 Hp, FRN 5.XX-9.30 - Manual (Page 55)

Chapter 3
Functional Description
3-22
Process Trim (Circle 7 )
Process Trim Reference (Parameter 161), and Process Trim Feedback
(Parameter 162), are summed to provide the error signal into the filter
block. Process Trim Filter Constant (Parameter 713), determines the gain
of a single pole filter used in the process trim. The output of the filter is
used as the input to the process trim P/I regulator. Process Trim KI Gain
(Parameter 715) controls the integral gain, and Process Trim KP
(Parameter 716), controls the proportional gain. The output of the PI
Control is limited by adjustable high and low limits. Process Trim Low
Limit (Parameter 717), specifies the low limit of the process trim trim
output value. Process Trim High Limit (Parameter 718), specifies the high
limit. Immediately prior to the the limit test, the output of the process trim
regulator is scaled by a gain factor. Process Trim Trim Output Gain
(Parameter 719), specifies the gain value to use. Process Trim Preload
(Parameter 714), is used to preset the integral term prior to enabling of the
process trim function. Logic Command bit 15, activates the process trim
function. Process Trim Select, (Parameter 628), contains one of three
selections for determining where the output of the process trim regulator
will be applied. Possible selections include trim velocity reference, trim
torque reference, or no use of the process trim output. If used to trim the
velocity reference, the output is summed with the velocity reference, to
produce Final Velocity Reference (Parameter 104). The sum will be
limited by Parameter 721 Proc Trim Lo Sum and Parameter 722 Proc Trim
Hi Sum. If used to trim the torque reference, the output is summed with
External Torque Command (Parameter 157), to produce an input to the
Torque Select block.
Torque Select (Circle 8)
Selects the reference input to the Current Control, based on the value of
Torque Mode (Parameter 625). Torque Mode is a number coded parameter
which allows operation under several different torque modes.
There are two possible reference inputs to choose from. The output of the
Velocity PI Control, which has been converted to a torque reference, is
used as an internal torque reference. If the drive is a stand alone drive, or
considered the Master drive of a system, this reference could be used. The
external Torque Reference, (Parameter 157), is used to supply an external
torque reference for the drive. This could be used if the drive was a slave
drive in a system. This parameter can also be modified by summing the
Process Trim Output when the Process Trim Select (Parameter 628) selects
the torque reference to trim. The external torque reference is also used
when either the “Min” or “Max” torque modes are selected. These
functions automatically make a selection between the external torque
reference value and the output of the Velocity PI Control.
Torque Command, (Parameter 110), indicates the latest torque reference
value. This value is converted to an armature current reference by dividing
by the motor Field Flux Command, to be used in the Current PI Control.
The value is also used as an input to the Droop Control.