Chapter 6 – Parameters
ACH 500 Programming Manual
6-29
In some mechanical systems, certain frequency ranges can cause resonance
problems. With this Group, it is possible to set up to five different frequency
ranges that the ACH 500 will skip over. For example, it is not necessary that
Parameter 20.5.4 (Crit Freq 2 Low) be greater than Parameter 20.5.3 (Crit
Freq 1 High), just as long as the Low parameter of any one set is lower than
the High parameter of the same set. Sets may overlap, but the skip will be
from the lower Low value to the higher High value.
To activate the Critical Frequency settings, select Parameter 20.5.1 (Crit Freq
Select)
YES
.
Note: Set unused Critical Frequencies to 0 Hz.
Example: Fan system with bad vibration from 18 Hz to 23 Hz and from 46 Hz
to 52 Hz. Running speed set to 60 Hz with reference. Set the parameters as
follows:
2 CRIT FREQ 1 LOW 18 Hz
3 CRIT FREQ 1 HIGH 23 Hz
4 CRIT FREQ 2 LOW 46 Hz
5 CRIT FREQ 2 HIGH 52 Hz
If, due to bearing wear, another resonance occurs at 34 – 36 Hz, the critical
frequency table can be added to as follows:
6 CRIT FREQ 3 LOW 34 Hz
7 CRIT FREQ 3 HIGH 36 Hz
Figure 6-11 shows the critical frequencies settings for fan vibration ranges
18 – 23 Hz and 46 – 52 Hz.
Figure 6-11 Critical Frequency Settings
f
1
Low
f
1
High
f
2
Low
f
2
High
f
ref
18
23
46
52
[Hz]
18
23
46
52
[Hz]
f
motor
