Danfoss VLT AQUA Drive FC 202

The ground leakage current is made up of several contri-
butions and depends on various system congurations,
including:
•
RFI ltering
•
Motor cable length
•
Motor cable shielding
•
Adjustable frequency drive power
130BB955.12
a
b
Leakage current
Motor cable length
Figure 3.6 Motor Cable Length and Power Size Inuence on
Leakage Current. Powersize a > Powersize b
The leakage current also depends on the line distortion.
130BB956.12
THVD=0%
THVD=5%
Leakage current
Figure 3.7 Line Distortion Inuences Leakage Current
Compliance with EN/IEC61800-5-1 (power drive system
product standard) requires special care if the leakage
current exceeds 3.5 mA. Reinforce grounding with the
following protective ground connection requirements:
•
Ground wire (terminal 95) of at least 10 mm
2
(7
AWG) cross-section.
•
Two separate ground wires both complying with
the dimensioning rules
See EN/IEC61800-5-1 and EN50178 for further information.
Using RCDs
Where residual current devices (RCDs), also known as
ground leakage circuit breakers (GLCBs), are used, comply
with the following:
•
Use RCDs of type B only as they are capable of
detecting AC and DC currents.
•
Use RCDs with a delay to prevent faults due to
transient ground currents.
•
Dimension RCDs according to the system congu-
ration and environmental considerations.
The leakage current includes several frequencies
originating from both the line power frequency and the
switching frequency. Whether the switching frequency is
detected depends on the type of RCD used.
130BB958.12
f
sw
Cable
150 Hz
3rd harmonics
50 Hz
Mains
RCD with low f
cut-
RCD with high f
cut-
Leakage current
Frequency
Figure 3.8 Main Contributions to Leakage Current
System Integration Design Guide
MG20N622 Danfoss A/S © 09/2014 All rights reserved. 53
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