Rockwell Automation 20D PowerFlex 700S with Phase I Control Reference Manual - Manual (Page 154)

154 Rockwell Automation Publication PFLEX-RM002D-EN-E - August 2013
Chapter 1 Detail Drive Configuration and Operation
Min Mode / Max Mode
This operating mode compares the speed and torque commands. The
algebraically minimum value is used. This mode can be thought of as a Speed
Limited Adjustable Torque operation. Instead of operating the drive as a pure
torque regulator, the “runaway” condition can be avoided by limiting the speed.
A winder is a good example for the application of the Min Spd/Trq operating
mode. Max mode would be used if both speed and torque are negative.
Figure 35 illustrates how min. mode operates. The drive starts out operating as a
torque regulator. The torque reference causes the motor to operate at 308rpm.
The speed reference is 468 rpm, so the minimum is to operate as a torque
regulator. While operating in torque regulation, the load decreases and the motor
speeds up. Notice the torque command has not changed. When the speed
regulator comes out of saturation, it clamps the speed and now the drive operates
as a speed regulator. The At Speed Relay then closes.
Figure 35 - Min Mode Operation
Sum Mode
Configuring the drive in this mode allows an external torque input to be summed
with the torque command generated by the speed regulator. The drive requires
both a speed reference and a torque reference to be linked. This mode can be used
for applications that have precise speed changes with critical time constraints. If
the torque requirement and timing is known for a given speed change, then the
external torque input can be used to preload the integrator. The timing of the
speed change and the application of an external torque command change must be
coordinated for this mode to be useful. The sum mode will then work as a feed
forward to the torque regulator.