6.5 Sine-wave Filters
When a drive controls a motor, resonance noise is heard
from the motor. This noise, which is the result of the motor
design, occurs every time an inverter switch in the drive is
activated. The frequency of the resonance noise thus
corresponds to the switching frequency of the drive.
Danfoss supplies a sine-wave
lter to dampen the acoustic
motor noise. The lter reduces the ramp-up time of the
voltage, the peak load voltage (U
PEAK
), and the ripple
current (ΔI) to the motor, which means that current and
voltage become almost sinusoidal. The acoustic motor
noise is reduced to a minimum.
The ripple current in the sine-wave
lter coils also causes
some noise. Solve the problem by integrating the lter in a
cabinet or enclosure.
For ordering numbers and more information on sine-wave
lters, refer to the Output Filters Design Guide.
6.6 dU/dt Filters
Danfoss supplies dU/dt lters which are dierential mode,
low-pass lters that reduce motor terminal phase-to-phase
peak voltages and reduce the rise time to a level that
lowers the stress on the insulation at the motor windings.
This is a typical issue with set-ups using short motor
cables.
Compared to sine-wave lters, the dU/dt lters have a cut-
o frequency above the switching frequency.
For ordering numbers and more information on dU/dt
lters, refer to the Output Filters Design Guide.
6.7
Common-mode Filters
High-frequency common-mode cores (HF-CM cores) reduce
electromagnetic interference and eliminate bearing
damage by electrical discharge. They are special nanocrys-
talline magnetic cores that have superior ltering
performance compared to regular ferrite cores. The HF-CM
core acts like a common-mode inductor between phases
and ground.
Installed around the 3 motor phases (U, V, W), the
common mode lters reduce high-frequency common-
mode currents. As a result, high-frequency electromagnetic
interference from the motor cable is reduced.
For ordering numbers refer to the Output Filters Design
Guide.
6.8
Harmonic Filters
The VLT
®
Advanced Harmonic Filters AHF 005 & AHF 010
should not be compared with traditional harmonic trap
lters. The Danfoss harmonic lters have been specially
designed to match the Danfoss drives.
By connecting the AHF 005 or AHF 010 in front of a
Danfoss drive, the total harmonic current distortion
generated back to the mains is reduced to 5% and 10%.
For ordering numbers and more information on how to
dimension brake resistors, refer to the VLT
®
Advanced
Harmonic Filters AHF 005/AHF 010 Design Guide.
6.9 High-power Kits
High-power kits, such as back-wall cooling, space heater,
mains shield, are available. See chapter 13.2 Ordering
Numbers for Options and Accessories for a brief description
and ordering numbers for all available kits.
Options and Accessories Ove... Design Guide
MG38C202 Danfoss A/S © 01/2018 All rights reserved. 35
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