Torque characteristics of high torque density partitioned PM consequent pole flux switching machines with flux barriers
Wasiq Ullah, Faisal Khan, Erwan Sulaıman, Muhammad Umair
Abstract
Unique double salient structure of Permanent Magnet Flux Switching Machines (PMFSM) with both Concentrated Armature Winding (CAW) and Permanent Magnet (PM) on stator attract researcher's interest for high speed brushless application when high torque density (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">den</sub> ) and power density (P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">den</sub> ) are the primal requirements. However, despite of stator leakage flux, high rare-earth PM usage, PMFSM is subjected to slot effects due to presence of both PM and CAW in stator and partial saturation due to double salient structure which generates cogging torque (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cog</sub> ), torque ripples (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rip</sub> ) and lower average torque (T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">avg</sub> ). To overcome aforesaid demerits, this paper presents Partitioned PM (PPM) Consequent Pole Flux Switching Machine (PPM-CPFSM) with flux barriers to enhance flux modulation, curtail PM usage and diminish stator leakage flux which reduces slotting effects and partial saturation to ultimately reduces T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cog</sub> and T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rlp</sub> . In comparison with the existing state of the art, proposed PPM-CPFSM reduces 46.53% of the total PM volume and offer T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">avg</sub> higher up to 88.8%, suppress T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rlp</sub> maximum up to 24.8%, diminish T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cog</sub> up to 22.74% and offer 2.45 times T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">den</sub> and P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">den</sub> . Furthermore, torque characteristics of proposed PPM-CPFSM is investigated utilizing space harmonics injection i.e. inverse cosine, inverse cosine with 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> harmonics and rotor pole shaping techniques i.e., eccentric circle, chamfering and notching. Detailed electromagnetic performance analysis reveals that harmonics injection suppressed T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cog</sub> maximum up to 83.5%, T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rip</sub> up to 40.72% at the cost of 4.71% T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">avg</sub> . Finally, rotor mechanical stress analysis is utilized for rotor withstand capability and 3D-FEA based Coupled Electromagnetic-Thermal Analysis (CETA) for thermal behavior of the developed PPM-CPFSM. CETA reveals that open space along PPM act as cooling duct that improve heat dissipation.