Danfoss VLT AutomationDrive Design Manual page 218

Electrical Installation
Very long control cables and analogue signals may in rare
cases and depending on installation result in 50/60Hz
earth loops due to noise from mains supply cables.
If this occurs, it may be necessary to break the screen or
insert a 100nF capacitor between screen and chassis.
The digital and analog inputs and outputs must be
connected separately to the frequency converter common
inputs (terminal 20, 55, 39) to avoid earth currents from
both groups to affect other groups. For example, switching
on the digital input may disturb the analog input signal.
Input polarity of control terminals
PNP (Source)
Digital input wiring
12 13 18 19 27
NPN (Sink)
Digital input wiring
12 13 18 19 27
NOTE
Control cables must be screened/armoured.
FC 300 Design Guide
29 32 33 20 37
29 32 33 20 37
®
MG.33.BD.02 - VLT is a registered Danfoss trademark
Connect the wires as described in the Operating
Instruction for the frequency converter. Remember to
connect the shields in a proper way to ensure optimum
electrical immunity.
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