Abstract The traction and power generation motors of hybrid electric vehicles need to provide greater output densities. This can be achieved by increasing output and reducing the physical size and weight of the motors. However, there are limits on how much a motor’s output can be increased while simultaneously shrinking the motor’s size, as it is conventionally structured. To address this issue, the authors developed a stator with a new structure to increase motor output and reduce motor size. By simultaneously optimizing magnetic circuit design, they increased maximum torque by 2.6% and maximum output by 8.9% and reduced volume by 23% and weight by 23% compared to motors of conventional structure, all while maintaining the same level of efficiency. The result was top-of-class output and compactness. 1. Introduction Vehicles running on electricity have spread rapidly in recent years to meet the need to reduce vehicle CO 2 emissions and achieve low fuel consumption. Such vehicles include hybrid electric vehicles (HEVs) and electric vehicles (EVs). Similar electric technologies are being used on vehicles ranging in size from compact to large, in a variety of types that include sedans, minivans and sport utility vehicles (SUVs). On the one hand, it is desirable that HEV series should expand to include medium-sized vehicles like minivans and SUVs. However, because there is less space for the engine room, there are limits on where motors of conventional structure can be placed, necessitating the development of smaller motors. The i-MMD (Intelligent Multi-Mode Drive) system, Honda’s full hybrid system, uses traction and power generation motors. The traction motor generates the driving force, which goes directly to the driveshaft. Among its other roles, it also regenerates power during braking. The role of the power generation motor is to take the output of the engine and use it to generate electricity, which it uses to charge the battery and provide power to the drive system ( 1).Traction motors in particular still need to provide higher torque, output and efficiency to meet the need for increased power performance and lower fuel consumption in vehicles. This paper reports on a structure that achieves higher output and smaller size, as well as on magnetic circuit design technology in an AC synchronous motor that combines the new-structure stator with an interior permanent magnet (IPM) rotor. 2. System Overview The i-MMD system is a high-efficiency hybrid system with a power train that combines an Atkinson cycle engine optimized for use specifically in HEVs with an electric-coupled CVT (e-CVT) containing two motors. The 2016 model minivan hybrid for the Japanese market uses this system. The position of this minivan hybrid in terms of fuel consumption and acceleration performance compared to other vehicles is shown in Figure 1. It has achieved both top-of-class power and fuel consumption performance as minivan. Figure 1. Fuel consumption and acceleration performanceNew-Structure Motor for Full Hybrid Electric Vehicle 2016-01-1225 Published 04/05/2016 Masashi Inoue, Hiromitsu Takamatsu, Masaki Ogami, Kenta Ninomiya, Kiyoshi Ito, and Takumi Shibata Honda R&D Co., Ltd. CITATION: Inoue, M., Takamatsu, H., Ogami, M., Ninomiya, K. et al., "New-Structure Motor for Full Hybrid Electric Vehicle," SAE Technical Paper 2016-01-1225, 2016, doi:10.4271/2016-01-1225. Copyright © 2016 SAE InternationalDownloaded from SAE International by Tsinghua University, Wednesday, February 20, 2019Figure 2 shows the overall configuration of main components newly developed for use in this minivan hybrid to use i-MMD system, while system specifications are given in Table 1 . The engine, e-CVT and power control unit (PCU), which is placed directly in the transmission case, are all mounted in the engine room, while the HEV battery is located under the first row seat. Figure 2. Overall system configuration Table 1. System Specificat