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enough. The maximum heat removal is occurred in stator yoke and the copper windings. The maximum observed temperature in stator slots is far from the insulation materials limits. The temperature developed in air gap and especially near the magnets is relatively low and there is no risk of magnets demagnetization. 4. Conclusions In this chapter, the perspective of direct-drive traction systems for HEVs, which lately con- centrates on increasing interest among researchers and manufacturers but is not adequately investigated in the literature, is examined. A design and optimization methodology for the devel- opment of high-power density in-wheel motors and the corresponding beneficial assessment of the overall HEV’s system performance is derived and discussed thoroughly. This approach is enhanced with the incorporation of a simple though efficient cooling system and the interaction of motor’s geometrical parameters and performance with the vehicle’s subsystems by using a dynamic HEV model. Through a case study, the particular problem requirements and con- straints, the eliminatory criteria and the motor’s topology selection strategy are illustrated and commented. Based on the overall results, the introduced methodology seems very promising and could be of great aid to designers in order to conclude to the optimal motor configuration. Author details Ioannis D. Chasiotis and Yannis L. Karnavas* *Address all correspondence to: karnavas@ee.duth.gr Department of Electrical & Computer Engineering, Electrical Machines Laboratory, Democritus University of Thrace, Xanthi, Hellas, Greece References [1] Kim H, Kim D. Comprehensive design methodology of input and output split hybrid electric vehicles. IEEE Transactions on Mechatronics. December 2016;21(6):2912-2913. DOI: 10.1109/TMECH.2016.2579646 [2] Kebriaeri M, Niasarm AH, Asaei B. Hybrid electric vehicles: An overview. In: Proceedings of International Conference on Connected Vehicles and Expo (ICCVE); 19-23 October 2015; IEEE, Shenzhen, China; 2015. pp. 299-305. DOI: 10.1109/ICCVE.2015.84 [3] Martinez CM, Hu X, Cao D, Velenis E, Gao B, Wellers M. Energy management in plug- in hybrid electric vehicles: recent progress and a connected vehicles perspective. IEEE Transactions on Vehicular Technology. Forthcoming. DOI: 10.1109/TVT.2016.2582721 Hybrid Electric Vehicles146