Danfoss VLT AQUA Drive Design Manual page 114

5. How to Install
5.2.13. Control Cable Length
Digital in / digital out
Dependent on what kind of electronics is being used, the maximum cable
impedance may be calculated based on the 4 kΩ frequency converter
input impedance.
NB!
Noise is always a factor to be reckoned with.
5.2.14. Electrical Installation, Control Cables
5
Illustration 5.10: Terminal 37: Safe Stop input available with Safe Stop Function only!
Very long control cables and analog signals may in rare cases and depending on installation result in 50/60 Hz earth loops due to noise from mains supply
cables.
If this occurs, you may have to break the screen or insert a 100 nF capacitor between screen and chassis.
114
Analog in / analog out
Again the electronics used puts a limitation on the cable length.
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MG.20.N4.02 - VLT is a registered Danfoss trademark
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VLT AQUA Drive Design Guide