4.1.2 Capacitor Disconnect
If the specific application requires a higher power factor at
no-load and the reduction of the capacitive current in stand-
by, a capacitor disconnect should be used. A contactor can
disconnect the capacitor at loads below 20%. It is important
to note that the capacitors may not be connected at full load
or disconnected at no load.
It is very important to consider the capacitive current in the
design of applications where the harmonic filter is supplied
by a generator. The capacitive current can overexcite the
generator in no-load and low-load condition. The over-
excitation causes an increase of the voltage that can exceed
the allowed voltage for the AHF and the frequency
converter. Therefore a capacitor disconnect should always be
used in generator applications and the design carefully
considered.
Compared to multi-pulse rectifiers, passive harmonic filter
(such as AHF) are more robust against background distortion
and supply imbalance. However, the performance of passive
filters is inferior to the performance of active filters when it
comes to partial load performance and power factor. For
details about the performance positioning of the various
harmonic mitigation solutions offered by Danfoss, please
consult the relevant harmonic mitigation literature.
Introduction to Advanced Ha...
AHF005/010 Design Guide
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