Commenced in January 2007
Frequency: Monthly
Edition: International
Paper Count: 32131
Transient Thermal Modeling of an Axial Flux Permanent Magnet (AFPM) Machine Using a Hybrid Thermal Model

Authors: J. Hey, D. A. Howey, R. Martinez-Botas, M. Lamperth


This paper presents the development of a hybrid thermal model for the EVO Electric AFM 140 Axial Flux Permanent Magnet (AFPM) machine as used in hybrid and electric vehicles. The adopted approach is based on a hybrid lumped parameter and finite difference method. The proposed method divides each motor component into regular elements which are connected together in a thermal resistance network representing all the physical connections in all three dimensions. The element shape and size are chosen according to the component geometry to ensure consistency. The fluid domain is lumped into one region with averaged heat transfer parameters connecting it to the solid domain. Some model parameters are obtained from Computation Fluid Dynamic (CFD) simulation and empirical data. The hybrid thermal model is described by a set of coupled linear first order differential equations which is discretised and solved iteratively to obtain the temperature profile. The computation involved is low and thus the model is suitable for transient temperature predictions. The maximum error in temperature prediction is 3.4% and the mean error is consistently lower than the mean error due to uncertainty in measurements. The details of the model development, temperature predictions and suggestions for design improvements are presented in this paper.

Keywords: Electric vehicle, hybrid thermal model, transient temperature prediction, Axial Flux Permanent Magnet machine.

Digital Object Identifier (DOI):

Procedia APA BibTeX Chicago EndNote Harvard JSON MLA RIS XML ISO 690 PDF Downloads 1995


[1] K. Sitapati and R. Krishnan, "Performance comparisons of radial and axial field, permanent-magnet, brushless machines," IEEE Transactions on Industry Applications, vol. 37, 2001, pp. 1219-1226.
[2] M.U. Lamperth, a Beaudet, and M. Jaensch, "Disc motors for automotive applications," Hybrid & Eco Friendly Vehicles Conference 2008 (HEVC 2008), 2008, pp. 10-10.
[3] H. Auinger, "Efficiency of electric motors under practical conditions," Power Engineering Journal, vol. 15, 2001, p. 163.
[4] J.F. Gieras, Axial Flux Permanent Magnet Brushless Machines, 2008.
[5] S. Scowby, "Thermal modelling of an axial flux permanent magnet machine," Applied Thermal Engineering, vol. 24, Feb. 2004, pp. 193- 207.
[6] T. Sebastian, "Temperature effects on torque production and efficiency of PM motors using NdFeB magnets," IEEE Transactions on Industry Applications, vol. 31, 1995, pp. 353-357.
[7] A. Boglietti, A. Cavagnino, D. Staton, M. Shanel, M. Mueller, and C. Mejuto, "Evolution and Modern Approaches for Thermal Analysis of Electrical Machines," IEEE Transactions on Industrial Electronics, vol. 56, Mar. 2009, pp. 871-882.
[8] D. Staton, a Boglietti, and a Cavagnino, "Solving the More Difficult Aspects of Electric Motor Thermal Analysis in Small and Medium Size Industrial Induction Motors," IEEE Transactions on Energy Conversion, vol. 20, Sep. 2005, pp. 620-628.
[9] P.H. Mellor, D. Roberts, and D.R. Turner, "Lumped parameter thermal model for electrical machines of TEFC design," IEE Proceedings B Electric Power Applications, vol. 138, 1991, p. 205.
[10] C.H. Lim, G. Airoldi, J.R. Bumby, R.G. Dominy, G.I. Ingram, K. Mahkamov, N.L. Brown, a Mebarki, and M. Shanel, "Experimental and CFD investigation of a lumped parameter thermal model of a singlesided, slotted axial flux generator," International Journal of Thermal Sciences, vol. 49, Sep. 2010, pp. 1732-1741.
[11] E. Odvárka, N.L. Brown, A. Mebarki, M. Shanel, S. Narayanan, and C. Ondrusek, "Thermal modelling of water-cooled axial-flux permanent magnet machine," 5th IET International Conference on Power Electronics, Machines and Drives (PEMD 2010), 2010, pp. 1-5.
[12] M. Tari, K. Yoshida, S. Sekito, J. Allison, R. Brutsch, a Lutz, and N. Frost, "A high voltage insulating system with increased thermal conductivity for turbo generators," Proceedings: Electrical Insulation Conference and Electrical Manufacturing and Coil Winding Technology Conference (Cat. No.03CH37480), 2001, pp. 613-617.
[13] E. Serre, P. Bontoux, and B. Launder, "Transitional-turbulent flow with heat transfer in a closed rotor-stator cavity," Journal of Turbulence, vol. 5, Feb. 2004.
[14] D. a Howey, a S. Holmes, and K.R. Pullen, "Radially resolved measurement of stator heat transfer in a rotor-stator disc system," International Journal of Heat and Mass Transfer, vol. 53, Jan. 2010, pp. 491-501.
[15] D.P. DeWitt, Fundamentals of heat and mass transfer, 1996.
[16] J. Nerg, M. Rilla, and J. Pyrhonen, "Thermal Analysis of Radial-Flux Electrical Machines With a High Power Density," IEEE Transactions on Industrial Electronics, vol. 55, Oct. 2008, pp. 3543-3554.