Considerations when Modernizing Drives for Buildings Based on an Energy Efficiency and Cost Perspective
Paper in proceeding, 2010

The efficiency consequence of keeping overdimensioned Induction Motors (IM) in Heating Ventilation and Air Conditioning (HVAC) applications, when modernizing such systems, using the potential that modern power electronic drives gives, is investigated in this paper. Five different Eff1 IM ratings in the range 1.1-4kW have been the target of the analysis. It is a common assumption that the motor efficiency drops rapidly as the load decreases below 75% its rated operation, which is the case for grid connected motors or motors operated with constant V/Hz ratio by an inverter. As a result, overdimensioning of the IM will result in increased energy cost compared to a smaller rating. However, by using a variable V/Hz ratio, it is shown here that the efficiency is in general highest for the largest IM regardless of the loading, despite the increase of the mechanical losses caused by increased cooling and friction. A conclusion found is that it is in principle always worth to keep an overdimensioned existing motor instead of replacing it with a smaller motor having a better efficiency class.

Building applications

Frequency converter

Energy savings

Induction motor


Johan Åström

Chalmers, Energy and Environment, Electric Power Engineering

Torbjörn Thiringer

Chalmers, Energy and Environment, Electric Power Engineering

The 9th International Power and Energy Conference IPEC 2010 Singapore

978-142447399-1 (ISBN)

Driving Forces

Sustainable development

Areas of Advance


Subject Categories

Other Electrical Engineering, Electronic Engineering, Information Engineering





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