Basic Cascade Controller - Danfoss VLT AQUA Drive FC 202 Design Manual

Application Examples
NOTICE
Set the analog input 2, (terminal 54) format to mA.
(switch 202).
Parameter Settings
Parameter
1-20 Motor Power [kW]/1-21 Motor Power [HP]
1-22 Motor Voltage
1-24 Motor Current
1-28 Motor Rotation Check
Enable reduced automatic motor adaptation in 1-29 Automatic
Motor Adaptation (AMA)
Table 4.3 Relevant Parameters for Submersible Pump
Application
Parameter
3-02 Minimum Reference
3-03 Maximum Reference
3-84 Initial Ramp Time
3-88 Final Ramp Time
3-41 Ramp 1 Ramp Up Time
3-42 Ramp 1 Ramp Down Time
4-11 Motor Speed Low Limit
[RPM]
4-13 Motor Speed High Limit
[RPM]
Use the Closed-loop wizard under Quick Menu_Function_Set-up, to
easily set up the feedback settings in the PID controller.
Table 4.4 Example of Settings for Submersible Pump
Application
Parameter
29-00 Pipe Fill Enable
29-04 Pipe Fill Rate
29-05 Filled Setpoint
Table 4.5 Example of Settings for Pipe-Fill Mode
Performance
Speed
Pipe Fill Vertical Pipes
Max. speed
Fill rate units/sec.
Min. speed
Initial ramp
Filled setpoint
Illustration 4.8 Pipe Fill-Mode, Performance Curve
MG20N602
Design Guide
Setting
The minimum reference unit
matches the unit in
20-12 Reference/Feedback Unit
The maximum reference unit
matches the unit in
20-12 Reference/Feedback Unit
(2 s)
(2 s)
(8 s depending on size)
(8 s depending on size)
(30 Hz)
(50/60 Hz)
Setting
(Feedback units/s)
(Feedback units)
Closed loop
Time
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4.3.2 BASIC Cascade Controller

The BASIC cascade controller is used for pump applications
where a certain pressure (head) or level must 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 variable speed (lead) motor as the variable
speed pump and can stage up to 2 additional constant
speed pumps on and off. Connect the additional constant
speed pumps directly to mains or via soft starters. By
varying the speed of the initial pump, variable speed
control of the entire system is provided. The variable
speed maintains constant pressure, which results in
reduced system stress, and quieter operation in pumping
systems.
Constant Speed
Pumps (2)
Variable Speed
Pumps (1)
Motor starter
Illustration 4.9 BASIC Cascade Controller
Fixed lead pump
The motors must be of equal size. The BASIC cascade
controller allows the frequency converter to control up to
3 equal pumps using the frequency converter's 2 built-in
relays. When the variable pump (lead) is connected directly
to the frequency converter, the 2 built-in relays control the
other two pumps. When lead pump alternations are
enabled, pumps are connected to the built-in relays and
the frequency converter can operate 2 pumps.
Lead pump alternation
The motors must be of equal size. This function makes it
possible to cycle the frequency converter between the
pumps in the system (maximum of 2 pumps). In this
operation, the run time between pumps is equalised,
reducing the required pump maintenance and increasing
reliability and lifetime of the system. The alternation of the
lead pump can take place at a command signal or at
staging (adding another pump).
Pressure Sensor
Frequency Converter
with
Cascade Controller
103
4 4