VLT
®
8000 AQUA
■
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 AFD
’
s 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 line cables can be used
as line supply to the AFD. 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
.
Assume:
Transmitter is scaled 0-10 Bar, minimum flow
is achieved at 30 Hz. An increase in motor
speed increases the pressure.
Set the following parameters:
Par. 100
Configuration
Closed loop [1]
Par. 201
Minimum Output Frequency
30 Hz
Par. 202
Maximum Output Frequency
50 Hz (or 60 Hz)
Par. 204
Minimum Reference
0 Bar
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 Bar
Par. 414
Maximum Feedback
10 Bar
Par. 415
Process units
Bar [16]
Par. 418
Setpoint 1
5 bar
Par. 420
PID control action
Normal
Par. 423
PID Proportional gain
0.3*
Par. 424
PID Integral time
30 sec.*
* The PID tuning parameters depend on the actual system dynamics.
MG.80.A7.22 - VLT is a registered Danfoss trademark
12
Rosewood STP ST42 General (Operation and Maintenance Manual - Part 4:
Section 6.3 Manufacturers Manuals 6.3.33 Danfoss VLT Aquadrive 8000) Vendor Manual
QP Id: VM207
Active: 03/09/2013
Page 18 of 208