Thermal limitations in air-cooled axial flux in-wheel motors for urban mobility vehicles: A preliminary analysis

The idea of having electric personal urban mobility vehicles that can be better supported within an urban infrastructure has been suggested for some time. Air-cooled in-wheel motors are preferred as they allow more passenger space and remove any plumbing requirements within the vehicle. This paper shows a preliminary analysis of the thermal limitations for axial flux internal rotor (AFIR) and axial flux internal stator (AFIS) machines. It is shown that AFIR type air-cooled machines favours low speed machines with traction power between 3.75kW-5kW and motor diameters between 13" and 15". This forces the traction power to be distributed on 3 or 4 wheels. Conversely the dependence of the cooling on the rotational speed in AFIS air-cooled machines favours high speed geared motors motor powers up to 7.5kW for a motor diameter of 15". This enables the traction power to be distributed on 2 wheels or more.

[1]  Klaus Fröhlich,et al.  Insulation Failure Mechanisms of Power Generators , 2008 .

[2]  A. Arkkio,et al.  Interdependence of Demagnetization, Loading, and Temperature Rise in a Permanent-Magnet Synchronous Motor , 2010, IEEE Transactions on Magnetics.

[3]  Jacek F. Gieras,et al.  Axial Flux Permanent Magnet Brushless Machines , 2005 .

[4]  T. Lipo,et al.  AXIAL FLUX PERMANENT MAGNET DISC MACHINES: A REVIEW , 2004 .

[5]  Song Liwei,et al.  Thermal effect on water cooling induction motor’s performance used for HEV , 2008, 2008 IEEE Vehicle Power and Propulsion Conference.

[6]  Sheldon S. Williamson,et al.  Suitability analysis of in-wheel motor direct drives for electric and hybrid electric vehicles , 2009, 2009 IEEE Electrical Power & Energy Conference (EPEC).

[7]  Malcolm McCulloch,et al.  Investigation into the temperature profile of a liquid cooled YASA© AFPM machine , 2012 .

[8]  S. K. Kauh,et al.  Efficiency Increase of an Induction Motor by Improving Cooling Performance , 2002, IEEE Power Engineering Review.

[9]  Ricardo Martinez-Botas,et al.  Transient Thermal Modeling of an Axial Flux Permanent Magnet (AFPM) Machine Using a Hybrid Thermal Model , 2010 .

[10]  K. Frohlich,et al.  Insulation Failure Mechanisms of Power Generators [Feature Article] , 2008, IEEE Electrical Insulation Magazine.

[11]  Martyn J. Anderson.  Unsprung Mass with In-Wheel Motors-Myths and Realities , 2010 .

[12]  F. Crescimbini,et al.  Compact wheel direct drive for EVs , 1996 .

[13]  D. Howey.  Thermal design of air-cooled axial flux permanent magnet machines , 2010 .

[14]  R. E. Nece,et al.  Chamber Dimension Effects on Induced Flow and Frictional Resistance of Enclosed Rotating Disks , 1960 .

[15]  J. Owen,et al.  Heat transfer from an air-cooled rotating disk , 1974, Proceedings of the Royal Society of London. A. Mathematical and Physical Sciences.

[16]  T.J. Woolmer,et al.  Analysis of the Yokeless And Segmented Armature Machine , 2007, 2007 IEEE International Electric Machines & Drives Conference.

[17]  E. C. Cobb,et al.  Heat transfer from a rotating disk , 1956, Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences.

[18]  Neil Brown,et al.  Thermal modelling of water-cooled Axial-Flux Permanent Magnet Machine , 2010 .

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

[20]  William J. Mitchell,et al.  Reinventing the Automobile: Personal Urban Mobility for the 21st Century , 2010 .

[21]  Z. Rahman,et al.  Evaluating radial, axial and transverse flux topologies for 'in-wheel' motor , 2004, Power Electronics in Transportation (IEEE Cat. No.04TH8756).

[22]  A. E. Emanuel.  A quantitative approach to estimate the life expectancy of motor insulation systems , 2002 .

[23]  Frank Kreith,et al.  Convection Heat Transfer in Rotating Systems , 1969 .

[24]  H. Oraee.  A quantative approach to estimate the life expectancy of motor insulation systems , 2000 .

[25]  N Künzli,et al.  Public-health impact of outdoor and traffic-related air pollution: a European assessment , 2000, The Lancet.

[26]  William Lark.  City-Car : optimizing vehicle and urban efficiencies through a shared adaptive platform , 2005 .

[27]  J. Owen.  The Reynolds analogy applied to flow between a rotating and a stationary disc , 1971 .

[28]  David L Buckeridge,et al.  Effect of motor vehicle emissions on respiratory health in an urban area. , 2002, Environmental health perspectives.

[29]  E.L. Brancato,et al.  Estimation of lifetime expectancies of motors , 1992, IEEE Electrical Insulation Magazine.

[30]  L. A. Dorfman,et al.  Hydrodynamic resistance and the heat loss of rotating solids , 1963 .

[31]  A. Di Napoli,et al.  Prototype of electric vehicle drive with twin water-cooled wheel direct drive motors , 1996, PESC Record. 27th Annual IEEE Power Electronics Specialists Conference.

[32]  Barrie Mecrow,et al.  Design of an in-wheel motor for a solar-powered electric vehicle , 1997 .

[33]  M. Jaensch,et al.  Disc motors for automotive applications , 2008 .

[34]  Giovanni Airoldi,et al.  Numerical investigations of air flow and heat transfer in axial flux permanent magnet electrical machines , 2010 .

[35]  S. A. D. Wiesche,et al.  Heat transfer from a rotating disk in a parallel air crossflow , 2007 .