Performance analysis of a coreless permanent magnet brushless motor

The paper deals with a new disk type PM brushless motor consisting of only stator (armature) winding and permanent magnet (PM) excitation system. No stator and rotor ferromagnetic cores have been used. To obtain the required value of the magnetic flux density in the air gap, PMs have been arranged in the so called "Halbach array". The FEM analysis has been done to prove that in a double sided motor with internal stator (twin PM rotor embracing a coreless stator), the peak value of the magnetic flux density can exceed 0.6 T. This is a sufficient value to design a high power density machine. A low speed 10 kW motor has approximately 1% higher efficiency and provides 82% more output power per kilogram than its cylindrical counterpart with a ferromagnetic core.