Investigation of Issues Related to Electrical Efficiency Improvements of Pump and Fan Drives in Buildings

Licentiate thesis, 2008

This thesis deals with issues related to efficiency of building related pump and fan drive systems. Different motor technologies are analyzed and a more detailed study on inverter fed Induction Machines (IM) is presented. A 4-pole, 4kW IM has been the focus of investigation, where different energy labels (eff1, eff2 and eff3), different voltage/frequency (V/Hz) control and different switching schemes of the frequency converter have been analyzed. Simulations as well as measurements have been performed with a close correlation of the results. The simulation results have then been used in order to analyze the saving potential for different load profiles. The general conclusion is that savings will be made during the life time of the drive system, both for an IM and frequency converter replacement. The analysis also show that the choice between an eff2 and eff1 IM, for the given load profiles, always generate the highest saving for the eff1 IM in economical terms, including the increased cost for an eff1 motor. It is interesting to note that, during the time period 1998-2003, eff2 label took 86% of the market share compared to eff1 8% and eff3 6%. It is also shown that losses introduced by the common over dimensioning of the pump and fan motor can result in increased energy efficiency with appropriate converter control compared with the use of a motor with lower rating. Finally, a study on modeling of the IM for bearing current prediction is presented containing a literature study and laboratory measurements.