Danfoss VLT 6000 HVAC User Manual

VLT
®
6000 HVAC
MG.60.B1.02 - VLT is a registered Danfoss trademark
8
Why use a frequency converter for controlling
fans and pumps?
A frequency converter takes advantage of the fact that
centrifugal fans and pumps follow the laws of
proportionality for such fans and pumps.
The graph below describes the laws of proportionality.
The graph shows that flow and pressure can be re-
gulated by changing the rpm figure.
■■
■■
■
The laws of proportionality
This figure describes the dependence of flow, pres-
sure and power consumption on the rpm figure.
Q = Flow
Q
1
= Rated flow
Q
2
= Reducing flow
H = Pressure
H
1
= Rated pressure
H
2
= Reducing pressure
P = Power
P
1
= Rated power
P
2
= Reducing power
n = Speed regulation
n
1
= Rated speed
n
2
= Reducing speed
The clear advantage - energy savings
The very clear advantage of using a frequency conver-
ter for controlling the speed of fans or pumps lies in
the electricity savings to be obtained.
When comparing with alternative regulating systems
and technologies, a frequency converter is the opti-
mum energy control system for regulating fan and
pump systems.
Example of energy savings
As can be seen from the figure (the laws of propor-
tionality), the flow is regulated by changing the rpm
figure. By reducing the speed only 20% from the rated
speed, the flow is also reduced by 20%. This is
because the flow is directly proportional to the rpm
figure. The consumption of electricity, however, is
reduced by 50%.
If the system in question only needs to be able to
supply a flow that corresponds to 100% a few days in
a year, while the average is below 80% of the rated
flow for the remainder of the year, the amount of
energy saved is even more than 50%.
■
■
Flow:
Q
1
=
n
1
Pressure:
H
1
=
(
n
1
)
2
Power:
P
1
=
(
n
1
)
3
Q
2
n
2
H
2
n
2
P
2
n
2

Danfoss VLT 6000 HVAC Specifications

General

Brand	Danfoss
Model	VLT 6000 HVAC
Category	DC Drives
Language	English