0093-9994 (c) 2019 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TIA.2019.2943447, IEEE Transactions on Industry Applications Optimal Design of TEFC Induction Machine and Experimental Prototype Testing for City Battery Electric Vehicle T.V. Tran 1 , E. Negre 1 , K. Mikati 2 , P. Pellerey 3 , B. Assaad 1 1 Department of Development Electric Powertrain, Renault S.A.S, Technocentre, Guyancourt, France, tuan-vu.t.tran-renexter@renault.com 2 Electric Motor and Gearbox Engineering Group, Nissan Motor Co. Ltd, NATC, Atsugi-shi, Kanagawa, Japan, karim-mikati@mail.nissan.co.jp 3 Drive System Engineering Departement, Tesla Inc., 3500 Deer Creek Rd, Palo Alto, CA 94304, USA, ppellerey@tesla.com Abstract—This paper presents the optimal design and experimental prototype testing of a low-cost motor applied for a city battery electric vehicle (BEV), zero emission A-segment. Respecting the car performance specifications, the aluminum cage rotor induction machine (IM) is designed to reduce motor cost using totally enclosed fan-cooled (TEFC) technology and a commercial speed encoder of internal combustion engine (ICE). An optimization approach and finite elements analysis (FEA) validation are coupled with thermal calculations and used to size the thermo-electromagnetic parts of the machine. The prototype is manufactured with full instrumentation. During the experiments, an indirect flux-oriented control model is built based on simulations in Matlab/Simulink environment. Using this real time control platform, the motor control is calibrated on the prototype in test-bench, to ensure the optimum energy consumption and the current and speed regulations in the entire large operating range. Finally, the experimental prototype testing results are shared to show the ideal design solution in term of peak performances, efficiency, thermal and NVH behaviors. Keywords—Battery electric vehicle, TEFC induction machine, optimal design, acoustic noise, experimental prototype testing. I. INTRODUCTION In the recent 10 years, the development and commercialization of electric vehicles has been dramatic. The battery, the main cost of electric vehicle has seen a significant reduction of its price. In 2016, the global electric car stock including BEV (battery electric vehicle) and PHEV (plug-in hybrid electric vehicle) surpassed 2 million vehicles in the worldwide after exceeding the 1 million thresholds in 2015 (*) . Every manufacturer proposes electric vehicles in its product portfolio. Most electric and hybrid vehicle motors currently on the market use permanent magnet synchronous machine (PMSM) like Toyota Prius, Nissan Leaf, Tesla Model 3, BMW i3, or electrically excited synchronous machine (EESM) like Renault Fluence, Zoé and others integrate induction machine (IM) like Cadillac CT6, Tesla Model S and X, Renault Twizy, Audi Q6 [1]. Because of a severe pollution problem, in Europe, several cities have begun planning to forbid internal combustion engine (ICE) cars in the coming years such as Paris, London, Oxford, Oslo, Hamburg, etc. Small city BEV may be a good alternative together with public transportation. This research focuses on the low-cost design of the whole electric traction motor for a city BEV. This car can have good driving performances if the peak torque-speed characteristic is well designed. High efficiency powertrain increases driving range. Low motor cost makes lower end-user price. The induction motor (IM) is well-known for its low-cost, reliability and simple manufacturing compared to the synchronous machines like permanent magnet synchronous machine (PMSM) and electrically excited synchronous machine (EESM) in traction applications [2-8]. The lower efficiency of rotor aluminum die-casting cage IM, compared to PMSM and EESM technologies [2-8], can partially be solved using copper cage [8-10]. In order to further reduce the cost of the IM, a totally enclosed fan-cooled (TEFC) system [10-13] and a commercially available ICE speed encoder are used. This design is more cost-effective compared to water cooling solutions [14-15] and systems that require position encoder, like the synchronous machines technologies. In the first section, the city BEV specifications will be detailed. The following section will describe the design process of the electric traction machine using an optimization approach. The fourth section will detail the instrumentation of the manufactured prototype. In the last section, the experimental results of the prototype on test-bench will be shown for peak performances, efficiency (motor and inverter), thermals (continuous performance and driving cycles) and NVH (noise, vibration and harshness). II. CITY BATTERY ELECTRIC VEHICLE SPECIFICATIONS The city BEV consists of a small 4-seaters car with a maximum load of 800 kg without passengers. The top speed of the vehicle is limited to 110 kph. Fig. 1 shows the acceleration of different small city cars A-segment for different drivers. The range required for the product is of 120 km per charge. Therefore, the requested specifications are: a maximum torque/power at the wheel of 1000 N.m / 45 kW, a (*) Global EV outlook 2017, OECD/International Energy Agency, 2017