Journal of Power Electronics

The Korean Institute of Power Electronics (전력전자학회)
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Evaluation of AC Resistance in Litz Wire Planar Spiral Coils for Wireless Power Transfer

  • Wang, Xiaona (Institute of Electrical Engineering, Naval University of Engineering) ;
  • Sun, Pan (Institute of Electrical Engineering, Naval University of Engineering) ;
  • Deng, Qijun (Department of Automation, Wuhan University) ;
  • Wang, Wengbin (State Grid Jiangxi Electric Power Research Institute)
  • Received : 2017.10.30
  • Accepted : 2018.03.01
  • Published : 2018.07.20
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Abstract

A relatively high operating frequency is required for efficient wireless power transfer (WPT). However, the alternating current (AC) resistance of coils increases sharply with operating frequency, which possibly degrades overall efficiency. Hence, the evaluation of coil AC resistance is critical in selecting operating frequency to achieve good efficiency. For a Litz wire coil, AC resistance is attributed to the magnetic field, which leads to the skin effect, the proximity effect, and the corresponding conductive resistance and inductive resistance in the coil. A numerical calculation method based on the Biot-Savart law is proposed to calculate magnetic field strength over strands in Litz wire planar spiral coils to evaluate their AC resistance. An optimized frequency can be found to achieve the maximum efficiency of a WPT system based on the predicted resistance. Sample coils are manufactured to verify the resistance analysis method. A prototype WPT system is set up to conduct the experiments. The experiments show that the proposed method can accurately predict the AC resistance of Litz wire planar spiral coils and the optimized operating frequency for maximum efficiency.

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References

  1. Y. Zhang, Z. Zhao, and K. Chen, "Frequency decrease analysis of resonant wireless power transfer," IEEE Trans. Power Electron., Vol. 29, No. 3, pp. 1058-1063, Mar. 2014. https://doi.org/10.1109/TPEL.2013.2277783
  2. J. Acero, R. Alonso, J. M. Burdio, L. A. Barragan, and D. Puyal, "Frequency-dependent resistance in Litz-wire planar windings for domestic induction heating appliances," IEEE Trans. Power Electron., Vol. 21, No. 4, pp. 856-866, Jul. 2006. https://doi.org/10.1109/TPEL.2006.876894
  3. C. Carretero, J. Acero, and R. Alonso, "TM-TE decomposition of power losses in multi-stranded Litz-wires used in electronic devices," Progr. Electromagn. Res., Vol. 123, pp. 83-103, Jan. 2012. https://doi.org/10.2528/PIER11091909
  4. J. Acero, P. J. Hernandez, J. M. Burdio, R. Alonso, and L. A. Barragan, "Simple resistance calculation in Litz-wire planar windings for induction cooking appliances," IEEE Trans. Magn., Vol. 41, No. 4, pp.1280-1288, Apr. 2005. https://doi.org/10.1109/TMAG.2005.844844
  5. X. Nan and C. R. Sullivan, "An equivalent complex permeability model for Litz-wire windings," IEEE Trans. Ind. Appl., Vol. 45, No. 2, pp. 854-860, Mar. 2009. https://doi.org/10.1109/TIA.2009.2013594
  6. X. Nan and C. R. Sullivan, "Simplified high-accuracy calculation of eddy-current loss in round-wire windings," in Proc. IEEE Power Electron. Spec. Conf. (PESC), pp. 873-879, 2004.
  7. Z. Pantic and S. Lukic, "Computationally-efficient, generalized expressions for the proximity-effect in multi-layer, multiturn tubular coils for wireless power transfer systems," IEEE Trans. Magn., Vol. 49, No. 11, pp. 5404-5416, Nov. 2013. https://doi.org/10.1109/TMAG.2013.2264486
  8. P. L. Dowell, "Effects of eddy currents in transformer windings," Proc. Inst. Elect. Eng., pt. B, Vol. 113, No. 8, pp. 1387-1394, Aug. 1966. https://doi.org/10.1049/piee.1966.0236
  9. D. Murthy-Bellur, N. Kondrath, and M. K. Kazimierczuk, "Transformer winding loss caused by skin and proximity effects including harmonics in PWM DC-DC flyback converter for continuous conductive mode," IET Power Electron., Vol. 4, No. 4, pp. 363-373, Feb. 2011. https://doi.org/10.1049/iet-pel.2010.0040
  10. R. P. Wojda and M. K. Kazimierczuk, "Winding resistance of Litz-wire and multi-strand inductors," IET Power Electron., Vol. 5, No. 2, pp. 257-268, Feb. 2012. https://doi.org/10.1049/iet-pel.2010.0359
  11. C. R. Sullivan, "Optimal choice for number of strands in a litz-wire transformer winding," IEEE Trans. Power Electron., Vol. 14, No. 2, pp. 283-291, Mar. 1999. https://doi.org/10.1109/63.750181
  12. F. Tourkhani and P. Viarouge, "Accurate analytical model of winding losses in round Litz-wire windings," IEEE Trans. Magn., Vol. 37, No.1, pp. 538-543, Jan. 2001. https://doi.org/10.1109/20.914375
  13. M. Bartoli, N. Noferi, A. Reatti, and M. K. Kazimierczuk, "Modeling Litz-wire winding losses in high-frequency power inductors," in IEEE Power Electronics Specialists Conf. (PESC) Rec., pp. 1690-1696, 1996.
  14. J. Acero, C. Carretero, I. Lope, R. Alonso, and J. M. Burdio, "FEA-bsed model of elliptic coils of square cross section," IEEE Trans. Magn., Vol. 50, No. 7, pp. 1-7, Feb. 2014.
  15. H. Rossmanith, M. Doebroenti, M. Albach, and D. Exner , "Measurement and characterization of high frequency losses in non-ideal Litz-wires," IEEE Trans. Power Electron., Vol. 26, No. 11, pp.3386-3394, Nov. 2011. https://doi.org/10.1109/TPEL.2011.2143729
  16. A. Rosskopf, E. Bar, and C. Joffe, "Influence of inner skin-and proximity effects on conductive in Litz-wires," IEEE Trans. Power Electron., Vol. 29, No. 10, pp. 5454-5461, Oct. 2006. https://doi.org/10.1109/TPEL.2013.2293847
  17. S. S. Mohan, M. M. Hershenson, S. P. Boyd, and T. H. Lee, "Simple accurate expressions for planar spiral inductances," IEEE J. Solid-state Circuits, Vol. 34, No. 10, pp. 1419-1424, Oct. 1999. https://doi.org/10.1109/4.792620
  18. M. Abramowitz and I. A. Stegun, Handbook of Mathematical Functions, Dover, 1970.
  19. M. K. Kazimierczuk and D. Czarkowski, "Class D currentdriven rectifiers," Ch. 2 in Resonant Power Converters, 2nd ed. Wiley-IEEE Press, Hoboken, NJ, 2011.