Cooling Channel Design and Temperature Field Analysis of a Lightweight High-Efficiency Drive Motor

Abstract

The temperature rise in lightweight, high-efficiency traction motors for new energy vehicles (NEVs) directly affects their operating efficiency, reliability, and service life. In this study, a permanent magnet synchronous motor (PMSM) for NEVs was selected as the research object, and three distributed cooling channel configurations, namely spiral, tree-shaped, and circumferential channels, were comparatively investigated using conjugate fluid–thermal simulations. The effects of cooling-channel configuration and coolant flow rate on the motor temperature and flow characteristics were analyzed. Under the rated operating condition with a total coolant flow rate of 10 L/min, the maximum motor temperatures of the spiral, tree-shaped, and circumferential configurations were 98.2 ℃, 97.2 ℃, and 99.6 ℃, respectively. The tree-shaped cooling channel, therefore, exhibited the best thermal performance and the smallest maximum inlet-to-outlet static gauge-pressure difference among the three configurations. Based on the thermal constraints and the variation in this defined pressure metric, recommended coolant flow rates of 12 L/min and 22 L/min were selected for the peak-speed and peak-torque operating conditions, respectively.

Keywords

New energy vehicle / Permanent magnet synchronous motor / Cooling channel / Conjugate heat transfer

References

[1] Wang L, Wang X, Gao P, Liu S . Torque ripple reduction analysis of interior permanent magnet synchronous motor for electric vehicle. Trans. China Electrotech. Soc. 2024, 39, 6386-6396. DOI: 10.19595/j.cnki.1000-6753.tces.231345

[2] Kim KS, Lee BH, Kim HJ, Hong JP, Jun JH . Thermal analysis of outer rotor type IPMSM using thermal equivalent circuit. In Proceedings of the International Conference on Electrical Machines and Systems, Sapporo, Japan, 21-24 October 2012; pp. 1-4.

[3] Kong X, Wang F, Xing J . Losses calculation and temperature field analysis of high-speed permanent magnet machines. Trans. China Electrotech. Soc. 2012, 27, 166-173. Available online: https://dgjsxb.ces-transaction.com/EN/abstract/abstract1728.shtml (accessed on 21 September 2026).

[4] Yoon MK, Jeon CS, Kauh SK . Efficiency increase of an induction motor by improving cooling performance. IEEE Trans. Energy Convers. 2002, 17, 1-6. DOI: 10.1109/60.986430

[5] Boglietti A, Cavagnino A, Staton D, Shanel M, Mueller M, Mejuto C. Evolution and modern approaches for thermal analysis of electrical machines. IEEE Trans. Ind. Electron. 2009, 56, 871-882. DOI: 10.1109/TIE.2008.2011622

[6] Wang Y, Lin Y . Equivalent model of temperature field and temperature field analysis of interior permanent magnet synchronous motor based on electromagnetic-thermal bidirectional coupling. Trans. China Electrotech. Soc. 2025, 40, 7127-7139. DOI: 10.19595/j.cnki.1000-6753.tces.241947

[7] Boglietti A, Cavagnino A, Lazzari M, Pastorelli MA. A simplified thermal model for variable-speed self-cooled industrial induction motor. IEEE Trans. Ind. Appl. 2003, 39, 945-952. DOI: 10.1109/TIA.2003.814555

[8] Lim CH, Airoldi G, Bumby JR, Dominy RG, Ingram GI, Mahkamov K, et al. Experimental and CFD investigation of a lumped parameter thermal model of a single-sided, slotted axial flux generator. Int. J. Therm. Sci. 2010, 49, 1732-1741. DOI: 10.1016/j.ijthermalsci.2010.03.018

[9] Ghahfarokhi PS, Kallaste A, Vaimann T, Rassolkin A, Belahcen A . Steady-state thermal model of a synchronous reluctance motor. In Proceedings of the 2018 IEEE 59th International Scientific Conference on Power and Electrical Engineering of Riga Technical University (RTUCON 2018), Riga, Latvia, 12-13 November 2018; pp. 1-5.

[10] Wahsh S, Shazly J, Yassin A . Steady-state heat conduction problems of AFPMSM using 3D finite element. In Proceedings of the 2016 Eighteenth International Middle East Power Systems Conference (MEPCON 2016), Cairo, Egypt, 27-29 December 2016; pp. 949-953.

[11] Zhou H, Wang X, Zhao W, Liu J, Xing Z, Peng Y . Rapid prediction of magnetic and temperature field based on hybrid subdomain method and finite-difference method for the interior permanent magnet synchronous motor. IEEE Trans. Transp. Electrification. 2024, 10, 6634-6651. DOI: 10.1109/TTE.2023.3334253

[12] Joo D, Cho JH, Woo K, Kim BT, Kim DK. Electromagnetic field and thermal linked analysis of interior permanent-magnet synchronous motor for agricultural electric vehicle. IEEE Trans. Magn. 2011, 47, 4242-4245. DOI: 10.1109/TMAG.2011.2149504

[13] Zhang K, Qi Y, Le B, Feng Z . Design and experimental study of water cooling system for external rotor permanent magnet synchronous motor. IEEE Access 2024, 12, 88034-88047. DOI: 10.1109/ACCESS.2024.3418017

[14] Ma Z, Bu Z, Cheng J . Research on water-cooling structure design of permanent magnet synchronous motor. Equip. Manag. Maint. 2025, 22-24. DOI: 10.16621/j.cnki.issn1001-0599.2025.05D.08

[15] Wang Y, Wang K, Zhu C . Analysis of temperature field and water-cooling heat dissipation of in-wheel motor. Intern. Combust. Engine Parts 2024, 1-4. DOI: 10.3969/j.issn.1674-957X.2024.23.001

[16] Wang X, Dai Y, Luo J . Waterway design and temperature field analysis of vehicle permanent magnet synchronous motor based on fluid-solid coupling. Trans. China Electrotech. Soc. 2019, 34 (S1), 22-29. DOI: 10.19595/j.cnki.1000-6753.tces.L80816

[17] Liu C, Lan Y, Li Y . Magnetic-thermal coupling analysis and channel optimization design of permanent magnet synchronous motor. Micromotors 2025, 58, 51-61. DOI: 10.15934/j.cnki.micromotors.2025.07.006

[18] Tang Y, Sun S, Yu W, Hua W . Thermal analysis of water-cooling permanent magnet synchronous machine for port traction electric vehicle. Electronics 2023, 12, 734. DOI: 10.3390/electronics12030734

[19] Jeon K, Park M, Park J, Choi H, Lee KD, Lee JJ, et al. Analysis of cooling characteristics of permanent magnet synchronous motor with different water jacket design using electromagnetic-thermal fluid coupled analysis and design of experiment. Machines 2023, 11, 903. DOI: 10.3390/machines11090903

[20] Zhang Z, Song Q, Wang X, Zhao S, Shah S WA . Reynolds-number-based optimization of a liquid cooling system for the permanent magnet synchronous motor of an electric vehicle. Case Stud. Therm. Eng. 2024, 60, 104720. DOI: 10.1016/j.csite.2024.104720

[21] Zhang Z, Song Q, Ahmed B, Han Y. Fluid and thermal effects on the temperature-dependent power increase of an electric vehicle’s permanent magnet synchronous motor using a compound water-cooling method. Case Stud. Therm. Eng. 2025, 65, 105543. DOI: 10.1016/j.csite.2024.105543

[22] Wan Y, Li Q, Guo J, Cui S . Thermal analysis of a Gramme-ring-winding high-speed permanent-magnet motor for pulsed alternator using CFD. IET Electr. Power Appl. 2020, 14, 2202-2211. DOI: 10.1049/iet-epa.2020.0086

[23] Versteeg HK, Malalasekera W. An Introduction to Computational Fluid Dynamics: The Finite Volume Method, 2nd ed.; Pearson Education Limited: Harlow, UK, 2007.

[24] Ding S, Cui G, Li Z, Guan T . Fluid and thermal performance analysis of PMSM used for driving. Heat Mass Transf. 2016, 52, 571-579. DOI: 10.1007/s00231-015-1581-8

[25] Guo C, Long L, Wu Y, Xu K, Ye H . Electromagnetic-thermal coupling analysis of a permanent-magnet in-wheel motor with cooling channels in the deepened stator slots. Case Stud. Therm. Eng. 2022, 35, 102158. DOI: 10.1016/j.csite.2022.102158

[26] Feng L, Ning Y, Zhang H, Feng Y, Wang M . Double-layer counter-flow cooling structure design and analysis of outer-rotor permanent magnet synchronous motors. Mach. Tool Hydraul. 2026, 54, 162-168. DOI: 10.3969/j.issn.1001-3881.2026.02.022

[27] Hu Y, Li J, Jia J, Zhao S, Cao J, Song F, et al. Structural optimisation of cooling waterway for vehicle motors based on fluid-solid coupling. Small Spec. Electr. Mach. 2025, 53, 33-37. Available online: https://www.wdj21.com/ssemj/CN/abstract/abstract1435.shtml (accessed on 16 September 2026).

[28] Liu L Wang D Chen D. Equivalent thermal network modeling and temperature field analysis of oil-cooled IPMSM. J. Hubei Univ. Automot. Technol. 2026, 40, 54-59. DOI: 10.3969/j.issn.1008-5483.2026.01.010

[29] Kang Y. Cooling structure design and temperature field analysis of electric vehicle drive motor. Electron. Commun. Comput. Sci. 2025, 7, 115-117. Available online: https://ojs.omniscient.sg/index.php/eccs/article/download/69593/68135/ (accessed on 16 September 2026).

[30] Wu B, Wan Z, Zhang K, Xi R, He M . Design of reentrant cooling channel in permanent magnet synchronous motor considering temperature field and flow field. Trans. China Electrotech. Soc. 2019, 34, 2306-2314. DOI: 10.19595/j.cnki.1000-6753.tces.171483

[31] Peng DQ, Zeng H, Zhang ZK, Yin W, Yan CS, Li G, et al. Simulation of enhanced heat dissipation performance of large permanent magnet synchronous motor with internal and external double cycles. J. Hunan Univ. (Nat. Sci.) 2024, 51, 195-203. DOI: 10.16339/j.cnki.hdxbzkb.2024239

[32] Gai Y, Chong YC, Adam H, Deng X, Popescu M, Goss J . Thermal analysis of an oil-cooled shaft for a 30,000 r/min automotive traction motor. IEEE Trans. Ind. Appl. 2020, 56, 6053-6061. DOI: 10.1109/TIA.2020.3025745

[33] Xu Z, Xu Y, Gai Y, Liu W . Thermal management of drive motor for transportation: Analysis methods, key factors in thermal analysis, and cooling methods-A review. IEEE Trans. Transp. Electrification. 2023, 9, 4751-4774. DOI: 10.1109/TTE.2023.3244907

[34] IEC 60349-4:2012; Electric traction-Rotating Electrical Machines for Rail and Road Vehicles-Part 4: Permanent Magnet Synchronous Electrical Machines Connected to an Electronic Converter. International Electrotechnical Commission: Geneva, Switzerland, 2012.

[35] IEC 60085:2007; Electrical Insulation-Thermal Evaluation and Designation. International Electrotechnical Commission: Geneva, Switzerland, 2007.