Rockwell Automation 1395 DC Drive, 800-1250 Hp, FRN 5.XX-9.30 - Manual (Page 38)

Chapter 3
Functional Description
3-5
Velocity Control
The Velocity Control compares the velocity reference to the velocity
feedback to determine the velocity error.
Torque Reference Select
The 1395 can operate as either a speed regulated or a torque regulated
drive, and therefore has the capability to accept either a velocity reference
or a torque reference input. In addition, the Torque Reference Select block
allows the drive to operate as a torque regulated drive and still have the
velocity control operational. In this case, the drive can receive both a
velocity reference and a torque reference at the same time. The Torque
Reference Select block selects from either the output of the Velocity
Control, or the External Torque Reference or both, depending on the mode
of operation being commanded from the Drive Logic Control block. The
reference which is selected is scaled based on the motor ratings to a current
reference.
Armature Current Control
Armature current reference is compared to the Armature Current Feedback
derived from the output of the current transformers (CT’s). The Armature
Current Control block produces a Voltage Reference which is applied to the
Armature Sync and Firing Logic. In addition, the Armature Current
Control monitors the Three-Phase AC Voltage and Armature Voltage
Feedback.
Armature Sync and Firing Logic
The Voltage Reference output from the Armature Current Control is
converted to a phase angle reference and then a time reference. The signal
is then synchronized to the incoming three-phase line to produce the gate
firing pulse for the SCRs located in the Armature Bridge. The Logic also
provides synchronizing information to the Field Sync and Firing Logic.
Field Flux Control
The Field Current Control uses the Field Flux Reference from the Velocity
Control to develop a field current reference. This reference is then
compared to the Field Current Feedback derived from the current
transformers in the incoming AC line to the Field Bridge. The error
between the field current reference and feedback produces a field Phase
Angle which is sent to the Field Sync and Firing Logic.