Harmonic Limitation Standards And Requirements; Harmonic Mitigation; Harmonic Calculation; Residual Current Device - Fc 300 Dg - Danfoss VLT AutomationDrive Design Manual

Electrical Installation
Non-linear
Current
Contribution to
system losses
8.10.3 Harmonic Limitation Standards and
Requirements
The requirements for harmonic limitation can be:
•
Application specific requirements
•
Standards that must be observed
The application specific requirements are related to a
specific installation where there are technical reasons for
limiting the harmonics.
8 8
Example: a 250kVA transformer with two 110kW motors
connected is sufficient if one of the motors is connected
directly on-line and the other is supplied through a
frequency converter. However, the transformer will be
undersized if both motors are frequency converter
supplied. Using additional means of harmonic reduction
within the installation or choosing low harmonic drive
variants makes it possible for both motors to run with
frequency converters.
There are various harmonic mitigation standards,
regulations and recommendations. Different standards
apply in different geographical areas and industries. The
following standards are the most common:
•
IEC61000-3-2
•
IEC61000-3-12
•
IEC61000-3-4
•
IEEE 519
•
G5/4
See the AHF005/010 Design Guide for specific details on
each standard.

8.10.4 Harmonic Mitigation

In cases where additional harmonic suppression is required
Danfoss offers a wide range of mitigation equipment.
These are:
•
VLT 12-pulse drives
•
VLT AHF filters
226
FC 300 Design Guide
System
Voltage
Impedance
Disturbance to
other users
MG.33.BD.02 - VLT
•
VLT Low Harmonic Drives
•
VLT Active Filters
The choice of the right solution depends on several
factors:
•
The grid (background distortion, mains
unbalance, resonance and type of supply
(transformer/generator)
•
Application (load profile, number of loads and
load size)
•
Local/national requirements/regulations (IEEE519,
IEC, G5/4, etc.)
•
Total cost of ownership (initial cost, efficiency,
maintenance, etc.)

8.10.5 Harmonic Calculation

Determining the degree of voltage pollution on the grid
and needed precaution is done with the Danfoss MCT31
calculation software. From www.danfoss.com you can
download the free tool VLT® Harmonic Calculation MCT 31.
The software is built with a focus on user-friendliness and
limited to involve only system parameters that are
normally accessible.

8.11 Residual Current Device - FC 300 DG

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 section Earth Leakage Current for further
information.
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