Helsinki University of Technology
Department of Electrical Engineering
Annual Report 2010
EFFDRI
Project title: Reduction of losses in electric drives (EFFDRI)
Decisions No. 124382, 124416
Persons who have worked for the consortium
Antero Arkkio, professor
Jorma Luomi, professor
Marko Hinkkanen, docent
Anna-Kaisa Repo, post-doc (-30.6.2009)
Huynh Van Khang, reasearcher, PhD student (15.9.2008-31.12.2010)
Tuomo Sipilä, MSc student (1.10.2008-31.5.2009)
Zengcai Qu, researcher, PhD student (1.10.2009-31.12.2010)
Jenni Pippuri, researcher, PhD student (1.11.2009-31.12.2010)
Paavo Rasilo, researcher, PhD student (1.7.2010-31.12.2010)
Abstract
Over 99 % of the electrical energy produced in Finland comes from rotating electrical
generators. About 65 % of this energy is transformed back to mechanical energy by electrical
motors. An increasing number of electrical motors is supplied from frequency converters.
The rotational speed of the electrical machine can be controlled by the frequency converter,
allowing huge amounts of energy to be saved in, e.g., pump and compressor applications.
However, the non-sinusoidal supply voltage from the frequency converter causes additional
losses in the electrical machine. When a typical 100 kW electric drive is operated at its rated
speed and power, there are around 6 kW of losses in the motor and 2 kW in the frequency
converter. These losses can be reduced by adjusting the control, but a reduction of the losses
in the electrical machine may lead to increased losses in the frequency converter, or vice
versa.
The aim is to develop a control algorithm for the frequency converter that minimises the total
losses of the electric drive. To reach this aim, comprehensive loss models are developed for
the finite element analysis of electrical machines and circuit analysis of frequency converters.
The finite element method (FEM) and circuit models are implemented in the
Matlab/Simulink environment, they are combined, and used for the identification of
parametric models for the total electromagnetic losses of the electric drive. An optimal
control algorithm for the frequency converter is searched for using the parametric models.
Publications
Belahcen A., Arkkio A., “Computation of additional losses due to rotor eccentricity in
electrical machines.” IET Electric Power Applications, 4 (2010) 4, pp. 259-266.
Dlala E., Belahcen A., Pippuri J., Arkkio A., “Interdependence of hysteresis and eddy-current
losses in laminated magnetic cores of electrical machines.” IEEE Transactions on Magnetics,
46 (2010) 2, pp. 306-309.
Dlala E., Belahcen A., Arkkio A., “On the importance of incorporating iron losses in the
magnetic field solution of electrical machines.” IEEE Transactions on Magnetics. 46 (2010)
8, pp. 3101-3104.
Helsinki University of Technology
Department of Electrical Engineering
Annual Report 2010
EFFDRI
M. Hinkkanen, L. Harnefors, and J. Luomi: “Reduced-order flux observers with statorresistance adaptation for speed-sensorless induction motor drives,” IEEE Trans. Pow.
Electron., vol. 25, no. 5, May 2010.
Islam M.J., Khang H.V., Repo A.-K., Arkkio A., “Eddy-current losses and temperature rise in
the form-wound stator winding of an inverter-fed cage induction motor.” IEEE Transactions
on Magnetics. 46 (2010) 8, pp. 3413-3416.
Mäkelä O., Repo A.-K., Arkkio A., “Numerical pulse test for synchronous machines.”
COMPEL – The International Journal for Computation and Mathematics in Electrical and
Electronic Engineering. 29 (2010) 5, pp. 1151-1158.
Lin R., Haavisto A., Arkkio A., “Analysis of eddy-current loss in end shield and frame of a
large induction machine.” IEEE Transactions on Magnetics, 46 (2010) 3, pp. 942-948.
Lin R., Haavisto A., Arkkio A., “Axial flux and eddy-current loss in active region of a largesized squirrel-cage induction motor.” IEEE Transactions on Magnetics. 46 (2010) 11, pp.
3933–3938.
Pippuri J.E., Belahcen A., Dlala E., Arkkio A., “Inclusion of eddy currents in laminations in
two-dimensional finite element analysis.” IEEE Transactions on Magnetics. 46 (2010) 8, pp.
2915–2918.
Arkkio A., Hannukainen A., Niemenmaa A., “Power balance for verifying torque
computation within time-discretized finite-element analysis.” EPNC 2010, 29.6-2.7.2010,
Dortmund, Germany. pp. 23-24.
Belahcen A.; Dlala E.; Pippuri J., “Modelling eddy-current in laminated non-linear magnetic
circuits.” EPNC 2010, 29.6-2.7.2010, Dortmund, Germany. pp. 9-10.
Belahcen A., Arkkio A., “Permanent magnets models and losses in 2D FEM simulation of
electrical machines.” ICEM2010. Rome, Italy, 6–8 September 2010. 6p.
M. Hinkkanen, T. Tuovinen, L. Harnefors, and J. Luomi: “A reduced-order position observer
with stator-resistance adaptation for PMSM drives,” in Proc. IEEE-ISIE'2010, Bari, Italy,
July 2010.
M. Hinkkanen, T. Tuovinen, L. Harnefors, and J. Luomi: “Analysis and design of a position
observer with stator-resistance adaptation for PMSM Drives,” in Proc. ICEM'2010, Rome,
Italy, Sept. 2010.
Khang H.V., Repo A.-K., Arkkio A., “Resistive loss identification of an inverter-fed deep-bar
induction motor.” Proceedings of SPEEDAM 2010. Pisa, Italy, 14-16 June 2010. pp. 105–
110.
Rasilo P., Arkkio A., “Modeling the effect of inverter supply on eddy-current losses in
synchronous machines.” Proceedings of SPEEDAM 2010. Pisa, Italy, 14-16 June 2010. pp.
861–865.
T. Tuovinen, M. Hinkkanen, L. Harnefors, and J. Luomi: “A reduced-order position observer
with stator-resistance adaptation for synchronous reluctance motor drives,” in Proc. EPEPEMC'2010, Ohrid, Macedonia, Sept. 2010.
Pippuri J.,”Finite element analysis of eddy current losses in steel laminations of inverter-fed
electrical machines.” TKK Dissertations 245, Aalto University, School of Science and
Technology, Espoo 2010. 135 p.
Helsinki University of Technology
Department of Electrical Engineering
Annual Report 2010
EFFDRI
M. Hinkkanen, T. Tuovinen, L. Harnefors, and J. Luomi: “A combined position and statorresistance observer for salient PMSM drives: design and stability analysis,” IEEE Trans.
Pow. Electron., in press.
Z. Qu, M. Ranta, M. Hinkkanen, and J. Luomi: “Loss-minimizing flux level control of
induction motor drives,” in Proc. IEEE IEMDC 2010, Niagara Falls, Canada, May 2011,
accepted.
The impact of the research (visits, co-operation between SusEn-projects,
international co-operation, interviews, other activities)
The Electric Drives Group has continued international co-operation with Dr. Lennart
Harnefors (ABB Power Systems, Sweden) in developing real-time observers for controlled
drives. In 2010, three conference papers and one journal paper have been written based on
this co-operation.
Jenni Pippuri from the Research Group of Electromechanics visited the electric drives group
at ABB Corporate Research, Baden, Switzerland, for four months.
The steering group of the project had two meetings: 22nd of May, 2010, and 5th of February,
2011. The members of the steering group from industry are Matti Kauhanen, chairman of the
group, ABB Oy, and Pertti Saransaari, Konecranes Oyj.
The progress of the research versus the original plan
Huynh Van Khang focused his study on the eddy-current losses in the stator and rotor
conductors of electrical machines. He estimated parametric models of induction motors from
the results of finite element analysis and measurements. The estimations have been done both
from time-domain and frequency-domain data. One journal paper and two conference papers
have been written of this topic. For validation measurements, a stator core of a 30 kW twopole induction motor was equipped with two stator windings for loss measurements. One of
the windings is used to supply the main flux, for instance a static flux, and the other winding
supplies a harmonic in the flux. In this way, we expect to be able to make accurate
measurements of the losses caused by voltage harmonics.
Jenni Pippuri defended her doctoral dissertation titled ”Finite element analysis of eddycurrent losses in steel laminations of inverter-fed electrical machines” on 5th of November,
2010.
Paavo Rasilo has developed methods for modelling the losses of inverter-fed salient-pole
synchronous machines and built up a calorimetric setup for measuring these losses.
The Electric Drives Group has developed flux observers with stator-resistance adaptation for
motion-sensorless (i) induction motor drives, (ii) permanent-magnet synchronous motor
drives, and (iii) synchronous reluctance motor drives. Analytical stabilizing gains have been
derived for these observers. The observers have been experimentally tested, and they can be
applied in real-time loss-minimizing control and loss monitoring. Two journal papers and
three conference papers have been written of this topic.
The resistance-adaptive flux observer for induction motor drives was combined with the
previously proposed dynamic core-loss model (which includes eddy-current and hysteresis
losses dissipated in the magnetically saturated stator core). Based on this model, a loss-
Helsinki University of Technology
Department of Electrical Engineering
Annual Report 2010
EFFDRI
minimizing flux level control scheme was proposed. The fast dynamics are achieved since the
optimal flux reference is solved at each sampling period and a flux controller is applied. The
method improves the accuracy of the loss minimization and torque production, it does not
require excessive computational resources, and it shows fast convergence to the optimum
flux level. The preliminary results will be published in a conference paper in May 2011, and a
journal manuscript is under preparation.
When the results of the research project are compared with the expected ones listed in the
research plan, most of the subtasks of the research plan have been completed successfully.
However, the combined circuit-FEM model for Matlab environment was not done and the
optimal switching frequency control was studied less than scheduled in the research plan.
One reason for these cuttings was the budget reduced by about 20% from the applied one.
During the project period 2008–2010, the research groups of Electromechanics and Electric
Drives published 16 journal papers and 15 conference papers on modelling and control of the
losses of electric drives.
Industrial co-operation if received industrial funding
No industrial funding.