Performance Analysis Of Novel Outer Rotor Permanent Magnet Machines With Similar Slot And Pole Numbers

Permanent magnet(PM)machines are widely used in military industry,aerospace,automobile and other fields for their high performance,reliable operation and miniaturization.Outer-rotor PM machines can obtain larger air gap diameter and inertia than inner-rotor PM machines in the same size because its rotor is outside,thus obtaining higher torque density.With the development and progress of science and technology,people have a higher pursuit of performance.Fractional-slot PM machines with similar numbers of slots and poles have the advantages of high torque density and low cogging torque.Therefore,this thesis takes the PM machine with similar numbers of slots and poles as the object,and analyses the influence of inner and outer rotor structure and unequal stator tooth width on the performance.Firstly,the basic equation of the similar numbers of slots and poles PM machine is analyzed and studied,and the winding factor of the similar numbers of slots and poles PM machine is deduced.The slot-pole matching of the similar numbers of slots and poles PM machine is studied and analyzed.According to the formula of wind ing factor derived and the method of magnet motive force analysis,the winding factor and magnet motive force of the 12-slot virtual motor are analyzed,and the matching pole number is found.Secondly,the finite element model of 12 slot/10 pole outer rotor PM machine is determined.On this basis,in order to achieve high torque density and high efficiency,four machines are designed and established for comparison.The amount of permanent magnets used in four machines and the electromagnetic properties of f our machines are compared and analyzed.Finally,the characteristics of magnetic field distribution and tooth flux density of PM machine with isolated teeth winding and similar numbers of slots and poles are analyzed.It is pointed out that the torque density of machine can be improved by reducing the tooth flux density of armature teeth with unequal tooth width structure.Five different schemes of stator tooth width are designed to simulate and verify the performance of 12 slot/10 pole PM machines.The reason why unequal teeth increase the torque density of machine is analyzed from two aspects of winding factor and tooth saturation.