Comparison of outer rotor PMSM with different pitch factors of q=1/2 and q=1/4 at same rotor geometry

Abstract

Due to high costs in producing distributed stator windings the fully automated produceable concentrated stator windings get more and more importance in many fields of applications. Especially in the field of automotive and traction applications, well known companies are using this kind of technology to reduce costs in producing AC windings. To achieve an acceptable torque per volume or utilisation factor which corresponds to a high winding factor a proper selection of the ratio between magnetic pole pairs and number of stator teeth, the pitch factor q, is essential. This paper discusses various properties of an outer rotor PMSM with same rotor geometry but two different stator configurations resulting in pitch factor of q=1/2 and q=1/4. The short circuit strength and sensorless control capability are important factors for the above mentioned applications because of reliability and low failure rate. Subsequently these essential properties are compared and discussed. As an important detail the short circuit current is calculated analytically and measured.