Danfoss VLT Series Design Manual page 129

VLT ® HVAC Drive Design Guide 6. Application Examples
6
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 speed
over a wide range is not an ideal solution because of low pump efficiency, and because there is
a practical limit of about 25% rated full load speed for running a pump.
With the BASIC Cascade Controller, the adjustable frequency drive controls a variable speed motor
as the variable speed pump (lead), and can stage up to two additional constant speed pumps to
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, resulting in re-
duced system stress and quieter operation in pumping systems.
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
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MG.11.B4.22 - VLT ® is a registered Danfoss trademark.