Delta Electronics ASDA-B Series manual Nlp, Use Notch Filter to suppress resonance

Chapter 6 Control Modes of OperationASDA-B Series

P2 - 25

NLP	Low-pass Filter Time Constant	Communication Addr.: 0219H
	(Resonance Suppression)
Default: 20		Related Section:
Applicable Control Mode: P/S/T		Section 6.3.7, P2-32
Unit: 0.1ms
Range: 0 ~ 10000
Settings:

This parameter is used to set low-pass filter time constant of resonance suppression.

0: Disabled

Use Notch Filter to suppress resonance

Gain	Resonance
	Point
	Low-pass
	Frequency
Resonance	Frequency
Frequency .

			Resonance
Gain	Gain		conditions
			is suppressed
Notch Filter
0db			Low-pass
Attenuation
			Frequency
Rate P2-24
Resonance	Frequency	Resonance	Frequency
Frequency		Frequency .
P2-23

Use Low-pass Filter to suppress resonance

Gain	Resonance	Gain
	Point
	Low-pass	0db
	Frequency
Resonance	Frequency
Frequency

	.							Resonance
		Low-pass Filter		Gain				conditions
Attenuation							is suppressed
Rate -3db		Cut-off Frequency
		of Low-pass Filter				Low-pass
		= 10000 / P2- -25 Hz				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 figures above). 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.

6-24 Revision January, 2009