High torque density PM motor for racing applications

Referring to a 4-wheel drive Formula Student Electric vehicle, a fractional-slot synchronous permanent magnet machine has been designed. Torque density has been improved adopting outer rotor topology and lightweight materials. An ironless rotor with PMs placed in an Halbach array configuration allows reduced rotor inertia to be obtained. The results described in the paper provide a quantitative assessment of the achievable torque density for small size motors.