Example Of Application - Constant Pressure Regulation In Water Supply System - Danfoss VLT 8000 AQUA series Operating Instructions Manual

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 a frequency converter enables the energy consumed by
the pumps to be kept at a minimum, while optimizing the water supply to consumers.
A VLT 8000 AQUA with its integral PID controller ensures simple and quick installation. For example, an
IP54/NEMA 12 unit can be mounted close to the pump on the wall and the existing mains cables can be
used as mains supply to the frequency converter. A Pressure transmitter (e.g. Danfoss MBS 33 or MBS
3000) can be fitted a few meters (feet) from the joint outlet point from the waterworks to obtain closed loop
regulation. Danfoss MBS 33 and MBS 3000 is a two-wire transmitter (4-20 mA) that can be powered directly
from a VLT 8000 AQUA. The required setpoint (e.g. 5 bar) can be set locally in parameter 418 Setpoint 1.
Set the following parameters:
Par. 100
Par. 201
Par. 202
Par. 204
Par. 205
Par. 302
Par. 314
Par. 315
Par. 316
Par. 403
Par. 404
Par. 405
Par. 406
Par. 413
Par. 414
Par. 415
Par. 418
Par. 420
Par. 423
Par. 424
* The PID tuning parameters depend on the actual system dynamics.
12
Configuration
Minimum Output Frequency
Maximum Output Frequency
Minimum Reference
Maximum Reference
Terminal 18 Digital inputs
Terminal 60, analog input current
Terminal 60, min. scaling
Terminal 60, max. scaling
Sleep mode timer
Sleep frequency
Wake-up frequency
Boost setpoint
Minimum Feedback
Maximum Feedback
Process units
Setpoint 1
PID control action
PID Proportional gain
PID Integral time
®
VLT 8000 AQUA
Assume:
Transmitter is scaled 0-10 Bar, minimum flow
is achieved at 30 Hz. An increase in motor
speed increases the pressure.
Closed loop [1]
30 Hz
50 Hz (or 60 Hz)
0 Bar
10 Bar
Start [1]
Feedback signal [2]
4 mA
20 mA
10 sec.
35 Hz
45 Hz
125%
0 Bar
10 Bar
Bar [16]
5 bar
Normal
0.3*
30 sec.*
MG.83.A2.02 - VLT is a registered Danfoss trademark