2-178 Speed/Torque Select
Torque Regulation Mode
A torque regulated application can be described as any process that requires
some tension control. An example of this is a winder or unwind where
material is being “drawn” or pulled with a specific tension required. The
process requires another element setting the speed. Configuring the drive
for torque regulation requires [Speed/Torque Mod] to be set to “2.” In
addition, a reference signal must be selected (Torque Ref A or Torque Ref
B). If an analog signal is used for the reference, select that from the Torque
Ref A or Torque Ref B selections.
When operating in a torque mode, the motor current will be adjusted to
achieve the desired torque. If the material being wound/unwound breaks,
the load will decrease dramatically and the motor can potentially go into a
“runaway” condition.
Figure 2.37
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 2.38
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
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