Danfoss VLT AQUA Drive Design Manual page 117

VLT ® AQUA Drive Design Guide
Set the smart logic control in par. 13-00 to ON.
Start/stop command is applied on terminal 18. If stop signal is applied, the adjustable frequency
drive will ramp down and go into free mode.
6.1.8. BASIC Cascade Controller
The BASIC Cascade Controller is used for
pump applications where a certain pressure
("head") or level needs to be maintained over
a wide dynamic range. Running a large pump
at variable speeds over a wide range is not an
ideal solution because of low pump efficiency
at lower speeds. In a practical way, the limit
is 25% of the rated full load speed for the
pump.
In the BASIC cascade controller, the adjusta-
ble frequency drive controls a variable speed
(lead) motor as the variable speed pump and
can stage up to two additional constant speed
pumps on and off. By varying the speed of the
initial pump, variable speed control of the en-
tire system is provided. This maintains con-
Fixed Lead Pump
The motors must be of equal size. The BASIC cascade controller allows the adjustable frequency
drive to control up to 3 equal size pumps using the drive's two built-in relays. When the variable
pump (lead) is connected directly to the drive, the other 2 pumps are controlled by the two built-
in relays. When lead pump alternations are enabled, pumps are connected to the built-in relays
and the drive is capable of operating 2 pumps.
MG.20.N2.22 - VLT ® is a registered Danfoss trademark.
6. Application Examples
stant pressure while eliminating pressure
surges, resulting in reduced system stress and
quieter operation in pumping systems.
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