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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
12
13
18
19
27
29
32
33
20
37
+24
VDC
0
VDC
130B
T106.10
PNP (Source)
Digital input wiring
NPN (Sink)
Digital input wiring
12
13
18
19
27
29
32
33
20
37
+24
VDC
0
VDC
130B
T107.11
NOTE
Control cables must be screened/armoured.
130B
T340.10
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.
Electrical Installation
FC 300 Design Guide
MG.33.BD.02 - VLT
®
is a registered Danfoss trademark
217
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