Sensorless electric traction drive with 500 Nm outer rotor permanent magnet synchronous machine

This paper presents calculations and measurements for a permanent magnet synchronous machine (PMSM) with buried magnets. Due to wide field weakening capability and high utilisation of this external rotor machine, it can be especially used for traction applications. The steady-state torque is about 346 Nm and overload torque at three times nominal current is about 580 Nm. Fractional-slot concentrated windings instead of distributed windings are used to increase the degree of automation. The short-circuit-proof machine is non forced air-cooled. The no-load torque ripple is calculated by numerical simulation and compared with measurement results. Also the so-called “Characteristic INFORM curves” for sensorless position control capability are presented. The efficiency curve of the machine provides high efficiency of 94 % over a wide operation range.