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 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 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 let only low frequencies 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 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 drive. The length is unfortunately limited because the filter does not reduce leakage currents in the cables.
3.7 High Power Options
3.7.1 Installation of Duct Cooling Kit in Rittal Enclosures
This section deals with the installation of IP00 / chassis enclosed frequency converters with duct work cooling kits in Rittal enclosures. In addition to the
enclosure a 200 mm base/plinth is required.
Illustration 3.29: Installation of IP00 in Rittal TS8 enclosure.
The minimum enclosure dimension is:
•
D3 and D4 frame: Depth 500 mm and width 600 mm.
•
E2 frame: Depth 600 mm and width 800 mm.
The maximum depth and width are as required by the installation. When using multiple frequency converters in one enclosure it is recommended that
each drive is mounted on its own back panel and supported along the mid-section of the panel. These duct work kits do not support the “in frame”
VLT
®
AQUA Drive Design Guide
3 VLT AQUA Selection
MG.20.N5.02 - VLT
®
is a registered Danfoss trademark
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