Energy Procedia 56 ( 2014 ) 525 – 531 Available online at www.sciencedirect.com ScienceDirect 1876-6102 © 2014 Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Peer-review under responsibility of COE of Sustainalble Energy System, Rajamangala University of Technology Thanyaburi (RMUTT)doi: 10.1016/j.egypro.2014.07.188 11th Eco-Energy and Materials Science and Engineering (11th EMSES) Design of Efficient In-Wheel Motor for Electric Vehicles Winai Chanpenga*, Prasert Hachanontb a,bDepartment of Mechanical Engineering, Faculty of Engineering, Rajamangala University of Technology Thanyaburi, Pathumthani, 12110, Thailand Abstract This research paper deals with the design and development of an in-wheel motor for electric vehicles. The proposed motor generates a 350-watt power drive with a power source of two 12V batteries. The batteries are connected in series to increase t he voltage to 24 volts and 18.23 A. The in-wheel motor is based on the principle of a DC electric motor to drive the vehicle whee ls so that the mechanical components of the transmission and the energy loss are minimized. The proposed in-wheel motor has 46 poles, 51 slots and 51 teeth. In addition, the method lowers the maintenance cost. This research work assumes the maximum weight of 70 kg and the running speed of 20 km/hr. The experiment results show that the output power and efficiency of the in- wheel motor are subject to the variation in input power given that the input voltage remains constant at 25.41 volts. The maximum efficiency of the in-wheel motor of 82.56% is achieved at 2.5 N-m torque. The maximum torque of 6.25 N-m is achieved with the input power of 348.76 watts. © 2014 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of COE of Sustainalble Energy System, Rajamangala University of Technology Thanyaburi (RMUTT). Keywords: In-Wheel Motor, Electric Vehicle, Power drive; 1. INTRODUCTION Most c urrent technological developments in electric vehicles have centered on improving energy efficiency. Several existing research studies thus focus on the deve lopment of vehicle propulsion and power transmission. The aim of this research study is to design and develop an in-wheel motor that reduces the power loss and power transmission in the vehicles. In particular, [1], [2] and [3] researched and developed the in-wheel motor technology * Winai Chanpeng. Tel.: +668-6414-3262; fax: +662-549-3432. E-mail address: winai.c@en.rmutt.ac.th © 2014 Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Peer-review under responsibility of COE of Sustainalble Energy System, Rajamangala University of Technology Thanyaburi (RMUTT)526 Winai Chanpeng and Prasert Hachanont / Energy Procedia 56 ( 2014 ) 525 – 531 for electric vehicles. The in-wheel motor technology requires the mounting of an electric motor directly on the wheel hub without gears or chains to minimize the number of mechanical power transm ission parts and thereby reduce the energy loss [4]. The in-wheel motor operates by converting the electric power from a car battery into mechanical energy to directly drive the wheels rather than through the pow er transmission part s. This therefore allows for more efficient use of energy. This research study focuses on the design and development of a small-scale in-wheel motor for electric vehicles. The design is based on the principle of a Blush Less DC Motor (BLDC). The experiments to study the performance of the in-wheel motor were carried out under a load condition of 70 kg in a laboratory setting. Nomenclature Pm drive power (watts) F total force to drive a vehicle (N) v vehicle velocity (m/s) Pe power supply (watts) K motor efficiency m number of winding turns per phase P number of poles I current (A) L conductor l