Design of a compact winding for an axial-flux permanent-magnet brushless DC motor used in an electric two-wheeler

This paper describes the design of a compact winding for an axial-flux permanent-magnet brushless dc motor used in an electric two-wheeler. Once the motor design is carried out using the conventional method and the dimensions of the motor, magnet, etc. are determined, the electric loading and the magnetomotive force (MMF) required to obtain the peak torque can be calculated. From the knowledge of the MMF requirement, a compact and efficient winding configuration has been achieved using a parametric study. The factors considered for the winding design are: 1) operating voltage; 2) number of poles; 3) cross-sectional area available for the winding; 4) conductor size; 5) number of parallel paths; 6) length of mean turn; 7) and the peak torque for a given value of AT/pole/phase. The motor voltage is decided based on the speed of the motor and aspects of the battery and the controller. The selected winding configuration for an 80-Nm peak torque, 48-V, three-phase motor is having 48 coils with each coil of 18 turns made out of 15 standard wire gauge copper wire. The resistance per phase is calculated as 0.0203 Omega.