Danfoss VLT DriveMotor FCP 106, Руководство по конструкции

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2.7 Leakage Current
2.7.1 Ground Leakage Current
Follow national and local codes regarding protective
earthing of equipment where leakage current exceeds 3.5
mA.
Frequency converter technology implies high frequency
switching at high power. This generates a leakage current
in the ground connection.
The ground leakage current is made up of several contri-
butions and depends on various system configurations,
including:
•
RFI filtering.
•
Motor cable length.
•
Motor cable screening.
•
Frequency converter power.
130BB955.12
a
b
Leakage current
Motor cable length
Illustration 2.21 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 2.22 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.
Product Overview
VLT
®
DriveMotor FCP 106/FCM 106
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