Rockwell Automation 20P PowerFlex Digital DC Drive - Manual (Page 285)

Rockwell Automation Publication 20P-UM001I-EN-P - February 2013 285
Application Notes Appendix C
Approximately half of the value of parameter 19 [S Curve Time] is added to the
initial “S” and half of the value is added to the final “S.”
When the S-shaped ramp > Linear ramp, the linear portion becomes zero.
To calculate the total ramp time when s-curve is enabled, the amount of time in
each section of the profile needs to be determined; T1 = initial S and final S, and
T2 = linear.
So, the total ramp time T3 = T1+T2+T1 (each ramp has two equal “S” portions
and one linear portion). In the following equations, Ta = linear ramp time (Pars
24, 32, 660, and 662), Ts = S-curve time (Par 19).
For S-shaped ramp <= Linear ramp
• T1 = (Ts * Ts) / (2 * Ta)
• T2 = Ta – T1
For S-shaped ramp > Linear ramp
• T1 = Ts/sqrt(2)
• T2 = 0
S-curve Acceleration Ramp Example:
Acceleration ramp parameter configuration:
• Par 18 [Ramp Type Select] = 1 “S shaped”
• Par 660 [Accel Time 1] = 5 s (Ta)
• Par 19 [S Curve Time] = 3.5 s (Ts)
In this case, S-shaped ramp <= Lramp, so T1 and T2 are calculated as:
T1 = (3.5 * 3.5) / (2 * 5)
T1 = 12.25 / 10
T1 = 1.23 s
T2 = 5 – 1.23
T2 = 3.78 s
The resulting total ramp time is calculated as:
T3 = 1.23 + 3.78 + 1.23
T3 = 6.24 s
Therefore, the total acceleration ramp time with S-curve enabled in this example
increased the total ramp time without S-curve by 1.24 seconds.