Rockwell Automation 20D PowerFlex 700S with Phase I Control Reference Manual - Manual (Page 61)

Rockwell Automation Publication PFLEX-RM002D-EN-E - August 2013 61
Detail Drive Configuration and Operation Chapter 1
Figure 21 - 10 Hz Notch
Conclusion
There are several filters used in the PowerFlex 700S for various applications.
The process trim uses a simple low pass filter to eliminate undesirable noise in the
feedback circuit. The cut off frequency of the low pass filter is set by parameter
184 [PI Lpass Filt BW]. Typical values would range from 15…20 rad/sec.
The speed loop uses a second order low pass filter after the speed error term is
developed. The cut off frequency of the second order low pass filter is by
parameter 89 [Spd Err Filt BW]. Typical value for this parameter is five times the
speed loop bandwidth (parameter 90 [Spd Reg BW]).
There are several lead lag filters used in the PowerFlex 700S. The lead lag filter has
two terms. The first term is the filter gain (Kn) and the second term is the filter
frequency (Wn). The filter can be used as “lag” to eliminate noise from entering
the control loop. The filter can be used as a “lead” to increase overall system
performance.
To eliminate noise (lag) use with the light or heavy filter.
To use the lead function:
• Set Wld equal to the desired lead in radians/second
• Set Wlg equal to 5x Wld
• Wn = Wlg
• Kn = Wlg/Wld
The torque reference has a notch filter used to eliminate resonance signals. The
notch frequency is set by parameter 118 [Notch Filt Freq]. This frequency is set
to the mechanical resonance in hertz.
Kn Wn
Light 0.7 35
Heavy 0.5 20