Danfoss VLT AutomationDrive FC 300 Series - RFI Switch; Residual Current Device; Final Setup and Test

1
2
PE
FC
PE
PLC
130BB922.11
PE PE
Illustration 7.65 Control Cable with Equalising Cable
1
Min. 16 mm
2
2 Equalizing cable
Table 7.38
50/60 Hz ground loops
With very long control cables, ground loops may occur. To
eliminate ground loops, connect one end of the screen-to-
ground with a 100nF capacitor (keeping leads short).
100nF
FC
PE
PE
PLC
130BB609.11
Illustration 7.66 Screen-to-ground Connected to a 100nF
Capacitor
Avoid EMC noise on serial communication
This terminal is connected to earth 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 7.67 Twisted-pair Cables
1
Min. 16 mm
2
2 Equalizing cable
Table 7.39
Alternatively, the connection to terminal 61 can be
omitted:
PE
FC
PE
FC
130BB924.11
PE PE
69
69
68
68
1
2
Illustration 7.68 Terminal 61 not Connected
1
Min. 16 mm
2
2 Equalizing cable
Table 7.40
7.8.4 RFI Switch
Mains supply isolated from earth
If the frequency converter is supplied from an isolated
mains source ( IT mains, floating delta) or TT/TN-S mains
with grounded leg (grounded delta), the RFI switch must
be turned off (OFF) via 14-50 RFI Filter.
In OFF, the internal capacitors between the chassis
(ground/earth), the input RFI filter and the intermediate
circuit are cut off. As the RFI switch is turned off, the
frequency converter will not be able to meet optimum
EMC performance.
By opening the RFI filter switch the earth leakage currents
are also reduced, but not the high-frequency leakage
currents caused by the switching of the inverter. It is
important to use isolation monitors that are capable for
use together with power electronics (IEC61557-8). E.g. Deif
type SIM-Q, Bender type IRDH 275/375 or similar.
Also refer to the application note VLT on IT mains.
NOTE
If the RFI switch is not turned off and the frequency
converter is running on isolated grids, earth faults can
potentially lead to charge up of the intermediate circuit
and cause DC capacitor damage or result in reduced
product life.
7.9 Residual Current Device
Use RCD relays, multiple protective earthing or earthing as
extra protection, provided that local safety regulations are
complied with.
If an earth fault appears, a DC content may develop in the
faulty current.
If RCD relays are used, local regulations must be observed.
Relays must be suitable for protection of 3-phase
equipment with a bridge rectifier and for a brief discharge
on power-up see 3.8 Earth Leakage Current for further
information.
7.10
Final Setup and Test
To test the setup and ensure that the frequency converter
is running, follow these steps.
Electrical Installation
VLT
®
AutomationDrive FC 300 Design Guide, 0.25-75 kW
MG33BE02 - VLT
®
is a registered Danfoss trademark 147
7 7
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