Efficiency improvement with intelligent control of induction motor drives

R. Mecke

 

2019/07/15

Abstract

The energy saving potential of induction motor drives is investigated. Two new aspects are identified, a multilevel frequency inverter and the speed control with variable rotor flux. Multilevel inverters with new wide-bandgap semiconductors for low voltage electrical drives (<1000 V)
reduce power semiconductor losses, voltage transients at the motor windings and harmonic losses in the cables. The power semiconductor losses of a two-level and a three-level inverter are
compared. At 20 kHz switching frequency the losses of the threelevel inverter are 38 % lower compared to the two-level inverter. Another efficiency improvement potential is the speed control
with variable rotor flux instead of commonly used constant flux. The rotor flux for maximum efficiency depends on the actual load and speed of the motor. The optimal rotor flux for maximum motor efficiency can be pre-calculated for each load and speed and implemented as reference value for rotor flux control in the frequency inverter. The maximum efficiency improvement with an 11 kW induction motor at small load reaches 35 % in motor and 45 % in generator operation mode. An increase in efficiency can be reached below 2/3 of rated torque in the whole speed range from 10 to 100 Hz.

Published in: Renewable Energy & Power Quality Journal (RE&PQJ, Nº. 17)
Pages: 337-342 Date of Publication: 2019/07/15
ISSN: 2172-038X Date of Current Version:2019/04/10
REF: 304-19 Issue Date: July 2019
DOI:10.24084/repqj17.304 Publisher: EA4EPQ

 

Authors and affiliations

R. Mecke
Department of Automation and Computer Sciences. Harz University of Applied Sciences. Wernigerode (Germany)

Key words

Energy efficiency, multilevel inverter, variable speed drive, vector control, rotor flux

References

[1] Koszescha, J., Advanced multilevel topologies: A technological breakthrough? Bodos Power Systems, pp. 14, 2010.
[2] Honsberg, M. & Radke, T., 3-level IGBT modules with trench gate IGBT and their thermal analysis in UPS, PFC
and PV operation modes. Proceedings of the European Conference on Power Electronics and Applications, 2009.
[3] Di Lella, M. & Ramin, R., IGBTs for 3-level inverters. Bodos Power Systems, pp. 22–24, 2008.
[4] Kioskeridis, I. & Margaris, N., Loss minimization in scalarcontrolled induction motor drives with search controllers.
IEEE Transactions on Power Electronics, Vol. 11, No. 2, pp. 213–220, 1996.
[5] Chen, S. & Nian Yeh, S., Optimal efficiency analysis of induction motors fed by variable-voltage and variablefrequency
source. IEEE Transactions on Energy Conversion, Vol. 7, No. 3, pp. 537–543, 1992.
[6] Tomta, G. & Nilsen, R., Analytical equations for three level NPC converters. Proceedings of the European Conference
on Power Electronics and Applications, 2001.
[7] Mecke, R., Efficient induction motor drive with multilevel inverter and variable rotor flux. Proceedings of the
International Symposium on Industrial Electronics, 2017.
[8] Mecke, R., Energy-efficiency control of induction machines with variable rotor flux. Proceedings of the European
Conference on Power Electronics and Applications, 2013.