Good practice

Optimising magnetic flux in ventilation frequency changers

Optimising magnetic flux in ventilation frequency changers
© aogreatkim, #162194132, 2019, source:
All sectors
Medium cost
Annual saving:
Payback time:
0.5 Year(s)
Associated cost savings: Energy:
1 - 3%
Payback time:
It cost only € 600 to optimise the system (payback in around half a year)
Total cost savings:
Return on investment: 173 % on annual savings of € 1 200
Size of company:
Small (less than 50)
Advancement in applying resource efficiency measures:
One off investment:

More flex in the flux...

  • Developments in solid-state electronics pave the way for more flexible and robust electric motors
  • Optimising the magnetic flux means motor speeds can be more easily adjusted and energy saved (1.5-3 % on annual consumption)

Micropolis in Northern Ostrobothnia, Finland was looking to optimise the efficiency of its ventilation equipment. The company identified the frequency changers as a likely source of efficiency gains. These electronic or electromechanical device convert bulk alternating current (AC) from one frequency to another when two adjacent power grids operate at different frequencies.

Frequency changers vary in power-handling capability from a few watts to megawatts. With the advent of solid-state electronics, it has become possible to build completely electronic frequency changers producing direct current at the desired frequency.

A variable-frequency drive is another type of changer used in AC motors such as pumps and fans. The speed of an AC motor depends on the frequency of the AC power supply, so altering the frequency allows the motor speed to be changed too. This means the fan or pump's output can be better adjusted to production and prevailing conditions, which provides remarkable energy savings.

Key benefits

  • Annual electricity consumption decreases by 1.5-3 % 
  • The optimisation process only cost € 600, so the estimated payback time is about half a year
  • That is a yield on the investment of 173 % with annual savings of € 1 200
  • Optimising frequency changers is an easy way to save energy with minimum investment costs

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