Delta Electronics none manual Use Low-pass Filter to suppress resonance

Chapter 6 Control Modes of OperationASDA-AB Series

Use Low-pass Filter to suppress resonance

Gain

Resonance

PointGain

.			Resonance
Low-pass Filter	Gain		conditions
		is suppressed
Attenuation
Rate -3db

Low-pass Frequency

0db

Cut-off Frequency
of Low-pass Filter	Low-pass
= 10000 / P2- -25 Hz	Frequency

Resonance Frequency Frequency

Frequency	Resonance	Frequency
	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.

Revision March 2008, Doc. Name: 2007PDD23000011 6-27