Cascade Controller Option - Danfoss VLT 8000 AQUA series Operating Instructions Manual

Cascade Controller Option

In "Standard Mode", one motor is controlled by
the drive that has the Cascade Controller Option
card installed in it. Up to four additional fixed speed
motors can be sequenced on & off, as required
by the process, in lead-lag mode.
In "Master/Slave Mode", the drive that has the
Cascade Controller option card installed in it, along
with its associated motor, is designated as the
master. Up to four additional motors, each with
its own drive, can be operated in slave mode. The
Cascade Controller functions to stage the slave
drives/motors - on & off (as required), as a function
of "best system operating efficiency".
In "Lead Pump Alternation Mode", it is possible to
average out the usage of the pumps. This is done by
making the frequency converter switch between the
pumps (max. 4) by means of a timer. Please note
that this mode requires an external relay setup.
Consult your Danfoss Sales Office for
additional information.
LC filters for VLT 8000 AQUA
When a motor is controlled by a frequency converter,
resonance noise will be heard from the motor. This
noise, which is caused by the design of the motor,
occurs each time one of the inverter switches in
the frequency converter is activated. Consequently,
the resonance noise frequency corresponds to the
switching frequency of the frequency converter.
For the VLT 8000 AQUA, Danfoss offers a LC filter
to dampen the acoustic motor noise.
Examples of the use of LC filters
Submersible pumps
For small motors with up to and including 5.5 kW
rated motor power, use an LC filter, unless the motor
is equipped with phase separation paper. This applies
e.g. to all wet running motors. If these motors are
used without LC filter in connection with a frequency
converter, the motor windings will short-circuit. If in
doubt, ask the motor manufacturer whether the motor
in question is equipped with phase separation paper.
Well pumps
If immersion pumps are used, e.g. submerged
pumps or well pumps, the supplier should be
contacted for clarification of requirements. It is
recommended to use a LC filter if a frequency converter
is used for well pump applications.
MG.83.A2.02 - VLT is a registered Danfoss trademark
®
VLT 8000 AQUA
This filter reduces the voltage rise time, the peak voltage
U and the ripple current
PEAK
making current and voltage almost sinusoidal. The
acoustic motor noise is therefore reduced to a minimum.
Because of the ripple current in the coils, there will be
some noise from the coils. This problem can be solved
entirely by integrating the filter in a cabinet or similar.
I to the motor, thereby
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