Temperature Field Accurate Modeling and Cooling Performance Evaluation of Direct-Drive Outer-Rotor Air-Cooling In-Wheel Motor

High power density outer-rotor motors commonly use water or oil cooling. A reasonable thermal design for outer-rotor air-cooling motors can effectively enhance the power density without the fluid circulating device. Research on the heat dissipation mechanism of an outer-rotor air-cooling motor can provide guidelines for the selection of the suitable cooling mode and the design of the cooling structure. This study investigates the temperature field of the motor through computational fluid dynamics (CFD) and presents a method to overcome the difficulties in building an accurate temperature field model. The proposed method mainly includes two aspects: a new method for calculating the equivalent thermal conductivity (ETC) of the air-gap in the laminar state and an equivalent treatment to the thermal circuit that comprises a hub, shaft, and bearings. Using an outer-rotor air-cooling in-wheel motor as an example, the temperature field of this motor is calculated numerically using the proposed method; the results are experimentally verified. The heat transfer rate (HTR) of each cooling path is obtained using the numerical results and analytic formulas. The influences of the structural parameters on temperature increases and the HTR of each cooling path are analyzed. Thereafter, the overload capability of the motor is analyzed in various overload conditions.

[1]  Andrea Cavagnino,et al.  Convection Heat Transfer and Flow Calculations Suitable for Electric Machines Thermal Models , 2008, IEEE Transactions on Industrial Electronics.

[2]  T. F. Chan,et al.  In-Wheel Permanent-Magnet Brushless DC Motor Drive for an Electric Bicycle , 2002, IEEE Power Engineering Review.

[3]  Shukang Cheng,et al.  Research on torque performance for permanent-magnet in-wheel motor , 2008, 2008 IEEE Vehicle Power and Propulsion Conference.

[4]  Shukang Cheng,et al.  Equivalent stator slot model of temperature field for high torque-density permanent magnet synchronous in-wheel motors accounting for winding type , 2016 .

[5]  V. Hatziathanassiou,et al.  Electrical-thermal coupled calculation of an asynchronous machine , 1994 .

[6]  Jie Ding,et al.  3D temperature field calculation of mine-used flame-proof integrative variable-speed system , 2015, 2015 IEEE 11th International Conference on Power Electronics and Drive Systems.

[7]  David A. Howey,et al.  Air-gap convection in a switched reluctance machine , 2015, 2015 Tenth International Conference on Ecological Vehicles and Renewable Energies (EVER).

[8]  G. Friedrich,et al.  Numerical approach for thermal analysis of heat transfer into a very narrow air gap of a totally enclosed permanent magnet integrated starter generator , 2015, 2015 IEEE Energy Conversion Congress and Exposition (ECCE).

[9]  Babak Fahimi,et al.  Thermal Modeling and Analysis of a Double-Stator Switched Reluctance Motor , 2015, IEEE Transactions on Energy Conversion.

[10]  V. Hatziathanassiou,et al.  Thermal analysis of an electrical machine taking into account the iron losses and the deep-bar effect , 1999 .

[11]  Wang Guo-hui.  Calculation and analysis of 3D temperature fields of medium size high voltage asynchronous motor based on coupled field , 2011 .

[12]  Rafal Wrobel,et al.  Thermal Performance of an Open-Slot Modular-Wound Machine With External Rotor , 2010, IEEE Transactions on Energy Conversion.

[13]  Li Liu,et al.  Simulation and Analysis of Thermal Fields of Rotor Multislots for Nonsalient-Pole Motor , 2015, IEEE Transactions on Industrial Electronics.

[14]  Andrea Cavagnino,et al.  Evolution and Modern Approaches for Thermal Analysis of Electrical Machines , 2009, IEEE Transactions on Industrial Electronics.

[15]  Tang Yue,et al.  Numerical calculation and optimization of fluid flow field of external fan of high voltage asynchronous motors , 2013 .

[16]  B. G. Fernandes,et al.  A High-Torque-Density Permanent-Magnet Free Motor for in-Wheel Electric Vehicle Application , 2012, IEEE Transactions on Industry Applications.

[17]  Chenglin Gu,et al.  There-dimensional temperature estimation of squirrel-cage induction motor using finite element method , 2011, 2011 International Conference on Electrical Machines and Systems.

[18]  Andrew S. Holmes,et al.  Air-Gap Convection in Rotating Electrical Machines , 2012, IEEE Transactions on Industrial Electronics.

[19]  Moo-Yeon Lee,et al.  Evaluation of the Effect of Operating Parameters on Thermal Performance of an Integrated Starter Generator in Hybrid Electric Vehicles , 2015 .