Analytical formulation for the torque enhancement of PM single-phase motor by a stator auxiliary magnet and a slotted PM rotor

The paper proposes an analytical formulation to calculate the torque generated by the interaction of two bonded permanent magnet (PM) rings, one of which slotted. Such procedure can be profitably used to improve the starting torque and mitigate both the slot cogging torque and the load torque ripple of single-phase brushless motors, provided with an auxiliary stator PM and a main rotor PM having suitably spaced slots on a portion of its length. The example of application show the benefits of the such arrangement with respect to a conventional PM design