Rockwell-automation 20B PowerFlex 70, PowerFlex 700 Reference Manual Manual de usuario descargar pdf (Pagina 158)

Skip Frequency

158 Rockwell Automation Publication PFLEX-RM001H-EN-P - June 2013

Skip Frequency Figure 31 Skip Frequency

Some machinery may have a resonant operating frequency that must be avoided

to minimize the risk of equipment damage. To assure that the motor cannot

continuously operate at one or more of the points, skip frequencies are used.

Parameters 084-086, ([Skip Frequency 1-3]) are available to set the frequencies to

be avoided.

The value programmed into the skip frequency parameters 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 parameter 87, [Skip Freq

Band]. The range is split, half above and half below the skip frequency parameter.

If the commanded frequency of the drive 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 will set the output frequency to the high value of the band.

See (A) in Figure 31

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 will

set the output frequency to the low value of the band. See (C) in Figure 31

Frequency

Time

(A)

(B)

Skip Frequency

Command

Frequency

Drive Output

Frequency

Skip + 1/2 Band

Skip – 1/2 Band

35 Hz

30 Hz

25 Hz

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Rockwell-automation 20B PowerFlex 70, PowerFlex 700 Reference Manual Manual de usuario Pagina 158