Output Filters; High Power Options - Danfoss VLT AQUA Drive FC 202 Design Manual

Selection

3.1.14 Output Filters

The high-speed switching of the frequency converter
produces some secondary effects, which influence the
motor and the enclosed environment. Two different filter
types, the dU/dt and the Sine-wave filters, are in place to
address these side effects.
dU/dt filters
The combination of rapid voltage and current increase
cause motor insulation stresses. The rapid energy changes
can also be reflected back to the DC-line in the inverter
and cause shut down. 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 frequency converter 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 let only low frequencies
pass. High frequencies are shunted away which results in a
sinusoidal phase to phase voltage waveform and sinusoidal
current waveforms.
With the sinusoidal waveforms, the use of special
frequency converter 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 frequency converter. The length is
unfortunately limited because the filter does not reduce
leakage currents in the cables.
MG20Z202
Design Guide

3.2 High Power Options

CAUTION
A door fan is required on the enclosure to remove the
heat losses not contained in the back channel of the
frequency converter and any additional losses generated
from other components installed inside the enclosure.
The total required air flow must be calculated so that the
appropriate fans can be selected. Some enclosure
manufacturers offer software for performing the
calculations (that is, Rittal Therm software). If the
frequency converter is the only heat generating
component in the enclosure, the minimum airflow
required at an ambient temperature of 45°C for the D3h
and D4h frequency converter is 391 m
minimum airflow required at an ambient temperature of
45°C for the E2 frequency converter is 782 m
cfm).
Danfoss A/S © Rev. 06/2014 All rights reserved.
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/h (230 cfm). The
3 /h (460
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