PowerFlex Digital DC Drive User Manual -
Publication 20P-UM001C-EN-P - July 2008
C-20
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 (e.g., 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 [Speed Up Gain Pct] = 50 %
•
Par 446 [Speed Up Base] = 14 rpm/ms
•
Par 447 [Speed Up Filter] = 20 ms
Speed Threshold Indicators
There are two speed threshold functions available that can be programmed
via a digital output to provide indication of when the drive has exceeded
certain set points.
Par 393 [Speed Threshold] displays whether the speed of the drive is above
or below a set speed for clockwise and counter-clockwise rotation. Set the
threshold speed for clockwise rotation in Par 101 [Spd Thresh Pos] and set
Figure C.2 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 C.3 Speed-up function active
The same drive with Speed-up function active.
Top: Par 122 [Spd Feedback]
Bottom: Par 199 [Arm Current Pct]
