Rockwell Automation 20B PowerFlex 70, PowerFlex 700 Reference Manual - Manual (Page 174)

Speed/Torque Select
174 Rockwell Automation Publication PFLEX-RM001H-EN-P - June 2013
Figure 38
Torque Reference:
[Torque Ref A Sel], parameter 427 is scaled by [Torque Ref A Hi] and [Torque
Ref A Lo]. Then divided by [Torq Ref A Div].
[Torque Ref B Sel], parameter 431 is scaled by [Torque Ref B Hi] and [Torque
Ref B Lo]. Then multiplied by [Torq Ref B Mult].
The final torque reference, in the Torque Mode, is the sum of scaled Torque Ref
A and scaled Torque Ref B.
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 39 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 468rpm, 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.
431
Scale
Scale
433
432
429
428
434
430
/
x +
Ref A Hi
Ref A Lo
Ref B Hi
Torq Ref A Div
Torq Ref B Mult
Ref B Lo
Torque Ref B Sel
427 Torque Ref A Sel