GE AF-600 FP Series Design And Installation Manual page 51

Application Set-Up Examples
6.3.3 Example of Energy Savings
As can be seen from the figure (Illustration 6.6), the flow is
controlled by changing the RPM. 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. 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%.
Illustration 6.6 describes the dependency of flow, pressure
and power consumption on RPM.
6 6
Illustration 6.6 The Laws of Proportionality
Q
1
Flow
:
Q
2
Pressure
:
P
1
Power :
P
2
Q = Flow
Q = Rated flow
1
Q = Reduced flow
2
H = Pressure
H = Rated pressure
1
H = Reduced pressure
2
P = Power
P = Rated power
1
P = Reduced power
2
n = Speed regulation
n = Rated speed
1
n = Reduced speed
2
48
n
1
=
n
2
( )
H n
2
1 1
=
H n
2 2
( )
n
3
1
=
n
2
TM
AF-600 FP Design and Installation Guide
6.3.4 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 PID control.
6.3.5 Cos φ Compensation
Generally speaking, the AF-600 FP has a cos φ of 1 and
provides power factor correction for the cos φ of the
motor, which means that there is no need to make
allowance for the cos φ of the motor when sizing the
power factor correction unit.
6.3.6 Using a Frequency Converter Saves
Money
The example on the following page shows that a lot of
equipment is not required when a frequency converter is
used. It is possible to calculate the cost of installing the
two different systems. In the example on the following
page, the two systems can be established at roughly the
same price.
DET-768b