A Comparative Study of Single-Rotor and Dualrotor Radial Flux Electric Machines for Centraldrive BEVs

This paper presents a comparative study between the state-of-the-art single-rotor permanent magnet machine and an innovative dual-rotor radial-flux permanent magnet machine used in automotive segment. The focus of this paper is placed on the battery electric vehicles where electrical machines in the range of 120 kW to 500 kW are being manufactured and designed for <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$B$</tex> to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$D$</tex> segments representing small to premium electric vehicles. The comparison is made taking into account major automotive attributes, where the focus is placed on efficiency. Considering the importance of the control, impact of the pulse-width modulation on the efficiency of the electrical machine is considered and a simulation methodology is proposed. This study is carried out on an electrical machine with the power of 255 kW designed and built for D-E segment passenger cars. It should however be noted that the results of this paper and the conclusion made may be extended also to other battery electric vehicles segments. The requirements and design presented in this study is based on central-drive propulsion architecture which covers majority of the passenger car market today, and in-wheel configuration is not taken into account.