Danfoss VLT AQUA Design Manual page 117

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VLT AQUA Drive Design Guide 6. Application Examples
Set the Smart Logic Control in par. 13-00 to ON.
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Start / stop command is applied on terminal 18. If stop signal is applied the frequency converter 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 cer- Fixed Lead Pump
tain pressure ("head") or level needs to be maintained over a wide
dynamic range. Running a large pump at variable speed over a wide
range is not an ideal solution because of low pump efficiency at lower
speed. In a practical way, the limit is 25% of the rated full load speed for
the pump.
In the BASIC Cascade Controller the frequency converter controls a var-
iable 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 entire system is provided.
This maintains constant pressure while eliminating pressure surges, re-
sulting in reduced system stress and quieter operation in pumping sys-
tems.
The motors must be of equal size. The BASIC Cascade Controller allows the frequency converter to control up to 3 equal size pumps using the drives 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 is enabled, pumps are connected to the built-in relays and the drive is capable of operating 2 pumps.
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MG.20.N3.02 - VLT is a registered Danfoss trademark