130BB955.12
a
b
Leakage current
Motor cable length
Illustration 3.6 Motor cable length and power size influence
on leakage current. Power size a > power size b
The leakage current also depends on the line distortion.
130BB956.12
THDv=0%
THDv=5%
Leakage current
Illustration 3.7 Line Distortion Influences Leakage Current
If the leakage current exceeds 3.5 mA, compliance with
EN/IEC61800-5-1 (power drive system product standard)
requires special care. Reinforce grounding with the
following protective ground connection requirements:
•
Ground wire (terminal 95) of at least 10 mm
2
cross-section.
•
2 separate ground wires both complying with the
dimensioning rules.
See EN/IEC61800-5-1 and EN 50178 for further information.
Using RCDs
Where residual current devices (RCDs), also known as earth
leakage circuit breakers (ELCBs), are used, comply with the
following:
•
Use RCDs of type B only as they can detect 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.
The leakage current includes several frequencies
originating from both the mains 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
Illustration 3.8 Main Contributions to Leakage Current
The amount of leakage current detected by the RCD
depends on the cut-off frequency of the RCD.
130BB957.11
Leakage current [mA]
100 Hz
2 kHz
100 kHz
Illustration 3.9 Influence of the RCD Cut-off Frequency on
Leakage Current
System Integration
VLT
®
Refrigeration Drive FC 103
48
Danfoss A/S © 08/2015 All rights reserved.
MG16G202
3
3
Содержание VLT FC 103
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