•
•
•
•
•
•
•
•
•
•
•
•
Typical value
(2)
40
39
Limit for R
SCE
≥ 120
(1)
(no limit applies because currents are above 75A)
1
According to IEC 61000-3-12:2011
2
The value depends on voltage range, power size and other factors. Please contact Danfoss to get information on specific values.
N O T I C E
It is the responsibility of the installer or user of the equipment to ensure that the equipment is connected only to a supply with a
short-circuit power S
SC
which is greater than or equal to what is specified below at the interface point between the users supply
and the public system (R
SCE
). If necessary, consult the distribution network operator.
S
SC
= 3 × R
SCE
× U
mains
× I
equ
= 3 × 120 × 400 × I
equ
Other power sizes can be connected to the public supply network by consultation with the distribution network operator.
10.17.5 Harmonic Mitigation
In cases where extra harmonic suppression is required, Danfoss offers a wide range of mitigation equipment. These are:
VLT® 12-pulse drives.
VLT® AHF filters.
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 (IEEE 519, IEC, G5/4, and so on).
Total cost of ownership (initial cost, efficiency, maintenance, and so on).
10.17.6 Harmonic Calculation
To determine the degree of voltage pollution on the grid and needed precaution, use the Danfoss MyDrive® Harmonics calculation
software. The free tool can be downloaded from
harmonics.mydrive.danfoss.com/
.
10.17.7 Line Reactors
A line reactor is an inductor which is wired in series between a power source and a load. Line reactors, also called input AC reactors,
are used in motor drive applications.
The main function of the line reactor is to limit the current. Line reactors also reduce the main harmonics, limit the inrush currents,
and protect drives and motors. Line reactors help achieving an overall improvement of the true power factor and the quality of the
input current waveform.
Line reactors are classified by their percent impedance (denoted as percent IZ or %IZ), which is the voltage drop due to impedance
at the rated current expressed as a percent of rated voltage. The most common line reactors have either 3% or 5% impedance.
When to use line reactors
It is important to consider where to install the drives. In some situations, disturbances from the grid can damage the drive and pre-
cautions must be taken to avoid this. To prevent disturbances, ensure that there is only a minimum of impedance in front of the
drive. Refer to
for advice on mitigation.
When calculating the impedance, also include the contribution from the supply transformer and the supply cables. In the following
situations, add impedance (line reactor or transformer) in front of the drive:
The installation site has switched power factor correction capacitors.
The installation site has lightning strikes or voltage spikes.
The installation site has power interruptions or voltage dips.
The transformer is too large compared to the drive.
Also, when planning load sharing applications, pay special attention to different enclosure size combinations and inrush concepts.
For technical advice on load sharing applications, contact Danfoss application support.
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Danfoss A/S © 2020.09
Electrical Installation
Considerations
VLT® AQUA Drive FC 202
Design Guide