Output Filters - Danfoss VLT FC 102 Series Design Manual

Selection
A
3 3
D
Figure 3.22 Enclosure Types B4 - C3 - C4
A Top cover
B Brim
C Base part
D Base cover
E Screw(s)
F Fan cover
G Top clip
Table 3.14 Legend to Figure 3.21 and Figure 3.21
72
C
Danfoss A/S © Rev. 06/2014 All rights reserved.
Design Guide
When option module A and/or option module B is/are
used, the brim (B) must be fitted to the top cover (A).
NOTICE!
G
Side-by-side installation is not possible when using the
IP21/IP4X/TYPE 1 Enclosure Kit.

3.1.15 Output Filters

The high speed switching of the adjustable frequency
drive produces some secondary effects, which influence
the motor and the enclosed environment. These side
effects are addressed by two different filter types, the
dU/dt and the sine-wave filter.
dU/dt filters
Motor insulation stresses are often caused by the
combination of rapid voltage and current increase. The
rapid energy changes can also be reflected back to the DC
line in the inverter and cause shutdown. The dU/dt filter is
designed to reduce the voltage rise time/the rapid energy
change in the motor and by that intervention avoid
premature aging and flashover in the motor insulation.
dU/dt filters have a positive influence on the radiation of
magnetic noise in the cable that connects the adjustable
frequency drive to the motor. The voltage wave form is
still pulse shaped but the dU/dt ratio is reduced in
comparison with the installation without filter.
Sine-wave filters
Sine-wave filters are designed to allow only low
frequencies to pass. High frequencies are consequently
shunted away, which results in a sinusoidal phase-to-phase
voltage waveform and sinusoidal current waveforms.
With the sinusoidal waveforms, the use of special
adjustable frequency drive motors with reinforced
insulation is no longer needed. The acoustic noise from the
motor is also damped as a consequence of the wave
condition.
Besides the features of the dU/dt filter, the sine-wave filter
also reduces insulation stress and bearing currents in the
motor thus leading to prolonged motor lifetime and longer
periods between services. Sine-wave filters enable use of
longer motor cables in applications where the motor is
installed far from the adjustable frequency drive. The
length is unfortunately limited because the filter does not
reduce leakage currents in the cables.
MG11BC22