What is the purpose of Noise Reduction [nrd] in an ATV61 or ATV71 Drive?

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Issue:
Why would you enable or disable Noise reduction in an ATV61 or ATV71 drive.

Product Line:
Altivar 61, Altivar 71

Environment:
All

Cause:
Documentation

Resolution:
The noise reduction parameter is default set to NO but can be set to YES for larger size ATV71 or ATV61 drives.
The range of drives that do not have this function are (D55M3) 75 HP and larger at 230 VAC and the (D90N4) 125 HP and larger at 460 VAC.
This is explained in the programming manual where the noise reduction parameter [nrd] is explained.

Noise Reduction:
- [No] : Fixed frequency. Factory setting at and above ATV71HD55M3X, ATV71HD90N4 and ATV71HC11Y.
- [Yes] : Frequency with random modulation. Factory setting up to ATV71HD45M3X, ATV71HD75N4 and ATV71HD90Y.
Random frequency modulation prevents any resonance, which may occur at a fixed frequency.