Finite-element analysis of eddy currents in the form-wound multi-conductor windings of electrical machines
Doctoral thesis (article-based)
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Verkkokirja (980 KB, 70 s.)
TKK dissertations, 211
AbstractThe aim of this research was to develop comprehensive numerical models for considering eddy currents and circulating currents in the form-wound multi-conductor windings of electrical machines and to study the effects of eddy currents and circulating currents. Time-harmonic and time-discretised finite-element methods were developed. The methods were applied to the stator winding of a 1250-kW cage induction motor and in both the stator and rotor windings of a 1.7-MW doubly-fed induction generator (DFIG). The series and parallel connections of the winding were taken into account. The Newton-Raphson iteration method was used to solve the system of non-linear equations. In time-harmonic FEM, the system of equations was solved iteratively just once for the steady-state solution. In time-discretised FEM, the system of equations was solved iteratively at every time step. The backward Euler method was used for the time discretisation. The radial distance of the stator bars from the air gap has a remarkable effect on losses and was found to be an important design parameter. A significant amount of stator-winding eddy-current loss can be reduced by considering this design parameter. A transposition of the conductors was implemented to reduce the circulating currents between the parallel stator conductors. The eddy-current effects in the form-wound multi-conductor windings of electrical machines were studied for both a sinusoidal and non-sinusoidal supply. A pulse-width-modulated (PWM) voltage supply was achieved by sinus triangle comparison and used as a non-sinusoidal supply for the machine. A PWM supply produced a significant amount of additional eddy-current losses in the form-wound stator winding of the cage induction motor when compared to the sinusoidal supply. The fundamental harmonic voltages of the sinusoidal and PWM supplies were equal for comparing the results. Similar sinusoidal and PWM voltages were used to supply the rotor winding of the DFIG as well. The additional eddy-current losses in the form-wound rotor winding as a result of the PWM supply were small.
Supervising professorArkkio, Antero, Prof.
eddy currents, finite-element analysis, form-wound, multi-conductor winding, cage induction motor, doubly-fed induction generator
- [Publication 1]: Islam, M. J.; Pippuri, J.; Perho, J.; Arkkio, A. 2007: Time-harmonic finite-element analysis of eddy currents in the form-wound stator winding of a cage induction motor, IET Electric Power Applications, Volume 1, Issue 5, September 2007, pp. 839-846.
- [Publication 2]: Islam, M. J.; Arkkio, A. 2008: Time-stepping finite-element analysis of eddy currents in the form-wound stator winding of a cage induction motor supplied from a sinusoidal voltage source, IET Electric Power Applications, Volume 2, Issue 4, July 2008, pp. 256-265.
- [Publication 3]: Islam, M. J.; Arkkio, A. 2009: Effects of pulse-width-modulated supply voltage on eddy currents in the form-wound stator winding of a cage induction motor, IET Electric Power Applications, Volume 3, Issue 1, January 2009, pp. 50-58.
- [Publication 4]: Islam, M. J.; Arkkio, A. 2008: Optimum supply for an inverter-fed cage induction motor at different load conditions, Proceedings of Nordic Workshop on Power and Industrial Electronics, 9 - 11 June 2008, TKK, Finland, 7 p. © 2008 by authors.
- [Publication 5]: Islam, M. J.; Arkkio, A. 2009: Finite-element discretisation for analysing eddy currents in the form-wound stator winding of a cage induction motor, CD Proceedings of the 14th International Symposium on Electromagnetic Fields in Mechatronics, Electrical and Electronic Engineering, 10 - 12 September 2009, Arras, France, 6 p.
- [Publication 6]: Islam, M. J.; Arkkio, A. 2009: Finite-element analysis of eddy currents in the form-wound multi-conductor windings of a doubly-fed induction generator, Report Series on Electromechanics, Report 75, Helsinki University of Technology, Espoo 2009, 20 p. ISSN 1456-6001, ISBN 978-952-248-206-8. © 2009 by authors.