Chapter 6 Control Modes of Operation|ASDA-A&A+ Series
6-30 Revision April 2009
Notch Filter
Usually, if the users know the resonance frequency, we recommend the users can eliminate the
resonance conditions directly by using notch filter (parameter P2-23, P2-24). However, the range of
frequency setting is from 50 to 1000Hz only and the range of resonant attenuation is 0~32 dB only.
Therefore, if the resonant frequency is out of this range, we recommend the users to use low-pass filter
(parameter P2-25) to improve resonant condition.
Please refer to the following figures and explanation to know how to use notch filter and low-pass filter
to improve resonant condition.
Use Notch Filter to suppress resonance
0db
Notch Filter
Attenuation
Rate P2-24
Resonance
Frequency
.
Resonance
Point
Gain
Frequency
.
Gain
Frequency
Gain
Frequency
Low-pass
Frequency
Low-pass
Frequency
Resonance
Frequency
P2-23
Resonance
conditions
is suppressed
Resonance
Frequency
Use Low-pass Filter to suppress resonance
Low-pass Filter
Cut-off Frequency
of Low-pass Filter
= 10000 / P2-25 Hz
-
0db
Resonance
conditions
is suppressed
.
.
Gain
Frequency
Gain
Frequency
Gain
Frequency
Low-pass
Frequency
Low-pass
Frequency
Resonance
Frequency
Attenuation
Rate -3db
Resonance
Point
Resonance
Frequency
When the low-pass filter (parameter P2-25) is adjusted from 0 to high value, the value of Low-pass
frequency will become smaller (see the figure on page 6-26). The resonant condition is improved but the
frequency response and phase margin will also decrease and the system may become unstable.
Therefore, if the users know the resonance frequency, the users can eliminate the resonance conditions
directly by using notch filter (parameter P2-23, P2-24). Usually, if the resonant frequency can be
recognized, we recommend the users can directly use notch filter (parameter P2-23, P2-24) to eliminate
the resonance. However, if the resonant frequency will drift or drift out of the notch filter range, we
recommend the users not to use notch filter and use low-pass filter to improve resonant conditions.
Call 1(800)985-6929 for Sales
Call 1(800)985-6929 for Sales
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