Danfoss VLT AutomationDrive FC 301 Series Design Manual page 147

Electrical Installation
Leakage current
Figure 9.37 Motor Cable Length and Power Size Influence on
Leakage Current. Powersize a > Powersize b
The leakage current also depends on the line distortion.
Leakage current
Figure 9.38 Line Distortion Influences Leakage Current
EN/IEC61800-5-1 (Power Drive System Product Standard)
requires special care if the leakage current exceeds 3.5 mA.
Grounding must be reinforced in one of the following
ways:
•
Ground wire (terminal 95) of at least 0.016 in
[10 mm 2 ]
•
Two separate ground wires both complying with
the dimensioning rules
MG33BF22
Design Guide
See EN/IEC61800-5-1 and EN50178 for further information.
a
Using RCDs
Where residual current devices (RCDs), also known as
ground leakage circuit breakers (GLCBs), are used, comply
with the following:
•
•
b
•
Motor cable length
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.
Leakage current
THVD=0%
THVD=5%
Figure 9.39 Main Contributions to Leakage Current
The amount of leakage current detected by the RCD
depends on the cut-off frequency of the RCD.
2
Rev. 2014-04-04 All rights reserved.
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 configu-
ration and environmental considerations
RCD with low f
cut-
RCD with high f
50 Hz 150 Hz
Mains 3rd harmonics
cut-
Frequency
f
sw
Cable
145
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