Novel rotor design for interior permanent magnet brushless machines: Initial investigation

This paper presents a novel rotor design for interior permanent magnet (IPM) brushless machines. Through the use of the novel rotor design the leakage flux in the rotor is reduced which increases the open circuit air-gap flux per pole. This results in an increase in the permanent magnet (PM) alignment torque of the machine. Other advantages of the novel rotor design include a reduction of the rotor inertia which brings benefits in the dynamic response of the machine and also a reduction of the rotor mass. A theoretical investigation is presented which shows the benefits of the rotor design for 4, 6 and 8 pole IPM machines. Furthermore, an experimental investigation is shown, using a small 4 pole IPM machine, with a conventional and a consequent pole rotor, which confirms the advantages shown in the theoretical investigation.