A novel circular winding brushless DC(CWBLDC) machine with low torque ripple

This paper proposes a novel circular winding brushless DC (CWBLDC) machine with low torque ripple. The multiphase armature winding of the machine is very similar to that of a brushed DC machine but with permanent magnet excitation on the rotor. Phase current commutation is realized by power electronic circuitry operating in either natural or forced commutation mode. By employing specific fractional-slot designs, the new machine drastically reduces the commutation torque ripple. Field-circuit coupled analyses have been performed for both integral-slot and fractional-slot designs. Simulation results show that torque ripple reduction through fractional-slot design is very effective. As the circular winding topology frees up constraints on 120° current conduction in three-phase BLDCs, the machine features improved torque density over conventional BLDCs. All above advantages makes this machine attractive for very-high-power motor drive applications. A 10 kW, 8-pole, 46-slot CWBLDC prototype has been designed, fabricated and tested to verify the analysis.