Thermal Analysis of Water Cooled ISG Based on a Thermal Equivalent Circuit Network

  • Kim, Kyu-Seob (Department of Automotive Engineering, Hanyang University) ;
  • Lee, Byeong-Hwa (Department of Electric Powertrain R&D Center, KATECH) ;
  • Jung, Jae-Woo (Department of brake electronic engineering team, R&D center, Hyundai Mobis) ;
  • Hong, Jung-Pyo (Department of Automotive Engineering, Hanyang University)
  • Received : 2013.08.02
  • Accepted : 2013.12.13
  • Published : 2014.05.01


Recently, the interior permanent synchronous motor (IPMSM) has been applied to an integrated starter and generator (ISG) for hybrid electric vehicles. In the design of such a motor, thermal analysis is necessary to maximize the power density because the loss is proportional to the power of a motor. Therefore, a cooling device as a heat sink is required internally. Generally, a cooling system designed with a water jacket structure is widely used for electric motors because it has advantages of simple structure and cooling effectiveness. An effective approach to analyze an electric machine with a water jacket is a thermal equivalent network. This network is composed of thermal resistance, a heat source, and thermal capacitance that consider the conduction, convection, and radiation. In particular, modeling of the cooling channel in a network is challenging owing to the flow of the coolant. In this paper, temperature prediction using a thermal equivalent network is performed in an ISG that has a water cooled system. Then, an experiment is conducted to verify the thermal equivalent network.


Cooling channel;Heat transfer of convection;Integrated starter and generator;Radiant heat;Thermal equivalent circuit network;Water jacket


  1. Chai Feng, Pei Yulong, Li Xinmei, Guo Bin, and Cheng Shukang, "The Performance Research of Starter-Generator Based on Reluctance Torque Used in HEV," IEEE Trans. on Magn., vol. 45, no. 1, pp. 635-638, 2009.
  2. Jin Hur and Byeong-Woo Kim, "Rotor Shape Design of an Interior PM Type BLDC Motor for Improving Mechanical Vibration and EMI Characteristics," JEET, vol. 5, no. 3, pp.462-467, 2010.
  3. V. Gnielinski, "New Equations for Heat and Mass Transfer in Turbulent Pipe and Channel Flow," American Institute of Chemical Engineer, vol. 16, no. 3, pp. 359-368, 1961.
  4. Yunus A. Cengel, Heat transfer: A practical approach, 2nd ed., McGraw-Hill, 2003
  5. P. H. Mellor, D. R. Roberts, D. Turner, "Lumped Parameter Thermal Model For Electrical Machines of TEFC Design," IEE, vol.138, no. 5, 1991.
  6. Byeong-Hwa Lee, Kyu-Seob Kim, Jae-Woo Jung, Jung-Pyo Hong, and Young-Kyoun Kim, "Temperature estimation of IPMSM using thermal equivalent circuit," IEEE Trans. on Magn., vol. 48, no. 11, pp. 2949-2952, 2012.
  7. Sunil Adhikari, Saman K. Halgamuge, and Harry C. Watson, "An Online Power-Balancing Strategy for a Parallel Hybrid Electric Vehicle Assisted by an Integrated Starter Generator," IEEE Trans. on Vehicular Technology, vol. 59, no. 6, pp. 2689-2699, 2010.
  8. Byeong-Hwa Lee, Soon-O Kwon, Tao Sun, Jung-Pyo Hong, Geun-Ho Lee, Jin Hur, "Modeling of Core Loss Resistance for d-q Equivalent Circuit Analysis of IPMSM considering Harmonic Linkage Flux," IEEE Trans. on Magn., vol. 47, no. 5, pp. 1066-1069, May 2011.
  9. G. H. Kang, J. P. Hong, G. T. Kim, J. W. Park, "Improved parameters modeling of interior permanent magnet synchronous motor by finite element analysis," IEEE Trans. on Magn., vol. 36, pp. 1867-1870, 2000.

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