Rockwell Automation 20P PowerFlex Digital DC Drive - Manual (Page 290)

290 Rockwell Automation Publication 20P-UM001I-EN-P - February 2013
Appendix C Application Notes
Speed Up Function
The Speed-up function is used to avoid oscillations in the presence of loads with a
high moment of inertia. When this function is enabled (default value of 0 “Speed
Up” in Par 1016 [SpdFuncSelect]), a D (derivative) value is added to the speed
feedback circuit, which allows you to increase the integral gain of the speed
regulator. It is also useful in the case of cyclical non-constant loads on the motor
(for example, cams). The feedback applied to the speed regulator is made of two
components:
• the motor speed
• the output signal from the Speed Up function
Parameters used in the example:
• Par 445 [Spd Up Gain Pct] = 50%
• Par 446 [Speed Up Base] = 14 rpm/ms
• Par 447 [Speed Up Filter] = 20 ms
Figure 81 - Speed-Up function inactive
Oscillation during a speed change due to a high moment of inertia.
Top: Par 122 [Spd Feedback]
Bottom: Par 199 [Arm Current Pct]
Figure 82 - Speed-up function active
The same drive with Speed-up function active.
Top: Par 122 [Spd Feedback]
Bottom: Par 199 [Arm Current Pct]