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.
Simpler installation when using a frequency con-
verter
A frequency converter can replace a traditional control
system, in which mechanical dampers and valves are
used for controlling flow or pressure.
The great advantage involved in using a frequency
converter is that the system becomes simpler, since a
lot of the mechanical and electrical equipment is no
longer required.
V-belts no longer required
In mechanical control systems, where the fan is driven
by V-belts, it is necessary to change belt pulleys in or-
der to adjust the fan speed to match the necessary
maximum load. Using a frequency converter, the V-
belts can be replaced by directly driven motors, whose
speed is changed simply by means of the frequency
converter.
The efficiency of the system improves and the entire
installation takes up less space. There is no dust from
the V-belt and less maintenance.
Regulating dampers and valves no longer re-
quired
Since the flow or pressure can be controlled by means
of the frequency converter, no regulating dampers and
valves are required in the system.
Cos φ compensation
Generally speaking, a frequency converter with a cos φ of 1 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.
Star/delta starter or soft-starter not required
When larger motors are started, it is necessary in
many countries to use equipment that limits the start-
up current. In more traditional systems, a star/delta
starter or soft-starter is widely used. Such motor start-
ers are not required if a frequency converter is used.
As illustrated in the figure below, a frequency converter
does not consume more than rated current.
1 = VLT 6000 HVAC
2 = Star/delta starter
3 = Soft-starter
4 = Start directly on mains
Cost of using frequency converter not higher
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 fol-
lowing page, the two systems can be established at
roughly the same price.
VLT
®
6000 HVAC Series
14 MG.61.B5.02 - VLT
®
is a registered Danfoss trademark
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