Rockwell Automation 20A PowerFlex 70EC/700VC - Manual (Page 94)

90 S Curve
Time to Accelerate
When accelerating from 0 to maximum speed, with maximum speed set to 60 Hz,
Ta = 2.0 sec, and S Curve = 25%, acceleration time is extended by 0.5 seconds (2.0
x 25%). When accelerating to only 30 Hz the amount of jerk control (S Curve) is
the same, but the extended amount of acceleration time is different.
Crossing Zero Speed
When the commanded frequency passes through zero, the frequency will S Curve
to zero and then S Curve to the commanded frequency as shown.
The following graph shows an acceleration time of 1.0 second. After 0.75 seconds,
the acceleration time is changed to 6.0 seconds. When the acceleration rate is
changed, the commanded rate is reduced to match the requested rate based on the
initial S Curve calculation. After reaching the new acceleration rate, the S Curve is
then changed to be a function of the new acceleration rate.
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Seconds
Hz
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
0.0 1.0 2.0 3.0 4.0 5.0
Seconds
Hz
-80.0
-60.0
-40.0
-20.0
0.0
20.0
40.0
60.0
80.0
0.0 1.0 2.0 3.0 4.0 5.0
Seconds
Hz
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0