2.5.5 Example with Varying Flow over 1
Year
The example below is calculated on the basis of pump
characteristics obtained from a pump datasheet.
The result obtained shows energy savings in excess of 50%
at the given flow distribution over a year. The pay back
period depends on the price per kWh and price of
frequency converter. In this example it is less than a year
when compared with valves and constant speed.
Energy savings
P
shaft
=P
shaft output
Flow distribution over 1 year
175HA209.11
60
50
40
30
20
10
H
s
0
100
200
300
400
(mwg)
B
C
A
750rpm
1050rpm
1350rpm
1650rpm
0
10
20
30
(kW)
40
50
60
200
100
300
(
m
3
/h
)
(
m
3
/h
)
400
750rpm
1050rpm
1350rpm
1650rpm
P
shaft
C
1
B
1
A
1
m
3
/
h
Distribution
Valve regulation
Frequency converter
control
% Hours Power Consumption
Power
Consumptio
n
A
1
-
B
1
kWh
A
1
- C
1
kWh
350
5
438
42.5
18,615
42.5
18,615
300
15
1314
38.5
50,589
29.0
38,106
250
20
1752
35.0
61,320
18.5
32,412
200
20
1752
31.5
55,188
11.5
20,148
150
20
1752
28.0
49,056
6.5
11,388
100
20
1752
23.0
40,296
3.5
6,132
Σ
100 8760
275,064
26,801
2.5.6 Better Control
If a frequency converter is used for controlling the flow or
pressure of a system, improved control is obtained.
A frequency converter can vary the speed of the fan or
pump, thereby obtaining variable control of flow and
pressure.
Furthermore, a frequency converter can quickly adapt the
speed of the fan or pump to new flow or pressure
conditions in the system.
Simple control of process (Flow, Level or Pressure) utilizing
the built-in PI control.
Safety and Conformity
VLT Micro Drive Design Guide
MG02K102 - VLT
®
is a registered Danfoss trademark
15
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