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VLT
®
6000 HVAC Series
■
Example of application - Constant pressure
regulation in water supply system
The demand for water from waterworks varies
considerably during the course of a day. In the night,
practically no water is used, while in the morning
and in the evening the consumption is high. In order
to maintain a suitable pressure in the water supply
lines in relation to the current demand, the water
supply pumps are equipped with speed control.
The use of frequency converters enables the energy
consumed by the pumps to be kept at a minimum,
while optimizing the water supply to consumers.
A VLT 6000 HVAC with its integral PID controller
ensures simple and quick installation. For example,
an IP54 unit can be mounted close to the pump on
the wall and the existing line cables can be used as
mains supply to the frequency converter. A Pressure
transmitter (e.g. Danfoss MBS 33 0-10) bar can
be fitted a couples of metres from the joint outlet
point from the waterworks to obtain closed loop
regulation. Danfoss MBS 33 is a two-wire transmitter
(4-20 mA) that can be powered directly from a VLT
6000 HVAC. The required setpoint (e.g. 5 bar) can
be set locally in parameter 418
Setpoint 1
.
Set the following parameters:
Par. 100
Configuration
Closed loop [1]
Par. 205
Maximum reference
10 bar
Par. 302
Terminal 18 Digital inputs
Start [1]
Par. 314
Terminal 60, analog input current
Feedback signal [2]
Par. 315
Terminal 60, min. scaling
4 mA
Par. 316
Terminal 60, max. scaling
20 mA
Par. 403
Sleep mode timer
10 sec.
Par. 404
Sleep frequency
15 Hz
Par. 405
Wake-up frequency
20 Hz
Par. 406
Boost setpoint
125%
Par. 413
Minimum feedback
0
Par. 414
Maximum feedback
10 bar
Par. 415
Process units
Bar [16]
Par. 418
Setpoint 1
5 bar
Par. 420
PID normal/inverse control
Normal
Par. 423
PID proportional gain
0.5-1.0
Par. 424
PID integration time
3-10
Par. 427
PID low pass filter
0.5-1.5
MG.61.A5.02 - VLT is a registered Danfoss trademark
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