- Loads that change quickly.
Typically, a class cannot be dened ahead of time without considering the intended equipment and processes to be used in
the environment. VLT
®
high-power drives observe the limits of Class 3 under typical supply system conditions (R
SC
>10 or
Vk
Line
<10%).
Harmonic order (h) Class 1 (V
h
%) Class 2 (V
h
%) Class 3 (V
h
%)
5 3 6 8
7 3 5 7
11 3 3.5 5
13 3 3 4.5
17 2 2 4
17˂h≤49 2.27 x (17/h) – 0.27 2.27 x (17/h) – 0.27 4.5 x (17/h) – 0.5
Table 10.45 Compatibility Levels for Harmonics
Class 1 Class 2 Class 3
THDv 5% 8% 10%
Table 10.46 Compatibility Levels for the Total Harmonic Voltage Distortion THDv
10.16.4 Harmonic Compliance
Danfoss drives comply with the following standards:
•
IEC61000-2-4
•
IEC61000-3-4
•
G5/4
10.16.5 Harmonic Mitigation
In cases where extra harmonic suppression is required, Danfoss oers the following mitigation equipment:
•
VLT
®
12-pulse Drives
•
VLT
®
Low Harmonic Drives
•
VLT
®
Advanced Harmonic Filters
•
VLT
®
Advanced Active Filters
Selecting the right solution depends on several factors:
•
The grid (background distortion, mains unbalance, resonance, and type of supply (transformer/generator).
•
Application (load
prole, number of loads, and load size).
•
Local/national requirements/regulations (such as IEEE 519, IEC, and G5/4).
•
Total cost of ownership (initial cost, eciency, and maintenance).
10.16.6 Harmonic Calculation
Use the free Danfoss MCT 31 calculation software to determine the degree of voltage pollution on the grid and needed
precaution. The VLT
®
Harmonic Calculation MCT 31 is available at www.danfoss.com.
Electrical Installation Con... Design Guide
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