A frequency converter takes advantage of the fact that centrifugal fans and pumps follow the laws of proportionality for such fans and pumps. For further

The Laws of Proportionality

information see the text

2.6.2. The clear advantage - energy savings

The very clear advantage of using a frequency converter for controlling the speed of fans or pumps lies in the electricity savings.

When comparing with alternative control systems and technologies, a frequency converter is the optimum energy control system for controlling fan and

pump systems.

Illustration 2.1: The graph is showing fan curves (A, B and C) for re-

duced fan volumes.

2.6.3. Example of energy savings

As can be seen from the figure (the laws of proportionality), 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 2.2: When using a frequency converter to reduce fan ca-

pacity to 60% - more than 50% energy savings may be obtained in

typical applications.

MG.11.B7.02 - VLT

is a registered Danfoss trademark

2. Introduction to VLT HVAC Drive

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