Allen-Bradley PowerFlex 70 Reference Manual page 153

Time to Max Speed
Note that S-curve time is defined for accelerating from 0 to maximum speed.
With maximum speed = 60 Hz, Ta = 2.0 sec, and S-curve = 25%, acceleration
time is extended by 0.5 seconds (2.0 * 25%). When accelerating to only 30 Hz the
acceleration time is still extended by the same amount of time.
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0
0.0 0.5
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.
80.0
60.0
40.0
20.0
0.0
-20.0
-40.0
-60.0
-80.0
0.0 1.0
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.
70.0
60.0
50.0
40.0
30.0
20.0
10.0
0.0
0.0 1.0
Rockwell Automation Publication PFLEX-RM001H-EN-P - June 2013
1.0 1.5 2.0
Seconds
2.0 3.0
Seconds
2.0 3.0
Seconds
S Curve
2.5 3.0
4.0 5.0
4.0 5.0
153