226 Rockwell Automation Publication 2198-UM001D-EN-P - May 2014
Appendix D Induction Motor Support
Skip Frequency
Some machines have a resonant operating frequency (vibration speed) that is
undesirable or could cause equipment damage. To guard against continuous
operation at one or more resonant points, you can configure the SkipSpeed
parameters in the Logix Designer application>Axis Properties>ParametersList
category.
The value programmed into the SkipSpeed1 parameter, sets the center point for
an entire skip band of frequencies. The width of the band (range of frequency
around the center point) is determined by the SkipSpeedBand parameter. The
range is split, half above and half below the SkipSpeed1 parameter.
If the commanded frequency is greater than or equal to the skip (center)
frequency and less than or equal to the high value of the band (skip plus 1/2
band), the drive sets the output frequency to the high value of the band. See (A)
in Figure 110
.
If the commanded frequency is less than the skip (center) frequency and greater
than or equal to the low value of the band (skip minus 1/2 band), the drive sets
the output frequency to the low value of the band. See (B) in Figure 110
.
Figure 110 - Skip Frequency
(A)
(A)
(B)
(B)
35 Hz
30 Hz
25 Hz
Time
Skip + 1/2 Band
Skip - 1/2 Band
Skip Frequency
Frequency
Command
Frequency
Drive Output
Frequency
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