3.5 Control Wiring Connection
•
Isolate control wiring from high power
components in the frequency converter.
•
If the frequency converter is connected to a
thermistor, for PELV isolation, optional thermistor
control wiring must be reinforced/double
insulated. A 24 V DC supply voltage is
recommended.
3.5.1 Access
All terminals to the control cables are located underneath
the LCP on the inside of the frequency converter. To
access, open the door (IP21/54) or remove the front panel
(IP20).
3.5.2 Using Screened Control Cables
Danfoss recommends braided screened/armoured cables to
optimise EMC immunity of the control cables and the EMC
emission from the motor cables.
3.5.3 Earthing (Grounding) of Screened
Control Cables
Correct screening
The preferred method in most cases is to secure control
and serial communication cables with screening clamps
provided at both ends to ensure best possible high
frequency cable contact. If the earth (ground) potential
between the frequency converter and the PLC is different,
electric noise may occur that will disturb the entire system.
Solve this problem by fitting an equalizing cable next to
the control cable. Minimum cable cross section: 16 mm
2
.
1
2
PE
FC
PE
PLC
130BB922.11
PE
PE
Illustration 3.12
1
Min. 16 mm
2
2
Equalizing cable
Table 3.6
50/60 Hz earth (ground) loops
With very long control cables, earth loops (ground loops)
may occur. To eliminate earth (ground) loops, connect one
end of the screen-to-earth (ground) with a 100 nF
capacitor (keeping leads short).
100nF
FC
PE
PE
PLC
130BB609.11
Illustration 3.13
Avoid EMC noise on serial communication
This terminal is connected to earth (ground) via an internal
RC link. Use twisted-pair cables to reduce interference
between conductors. The recommended method is shown
below:
PE
FC
PE
FC
130BB923.11
PE
PE
69
68
61
69
68
61
1
2
Illustration 3.14
1
Min. 16 mm
2
2
Equalizing cable
Table 3.7
Alternatively, the connection to terminal 61 can be
omitted:
PE
FC
PE
FC
130BB924.11
PE
PE
69
69
68
68
1
2
Illustration 3.15
1
Min. 16 mm
2
2
Equalizing cable
Table 3.8
Installation
VLT® Refrigeration Drive 110-250 kW Operating Instructions
18
MG16F102 - VLT® is a registered Danfoss trademark
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