Research On Performance Comparison Of Different Stator Modular Fractional-slot PM Machines

There are many kinds of modular permanent magnet(PM)machines for offshore wind power generation.Although all of them are easy to install,maintain and transport,the performance of the machines are very different.In addition to the modular type,the performance are also affected by slot pole configuration,stator gap width and tooth tip structure.Therefore,this thesis studies the performance of different stator modular PM machines.The modular structure are divided into two categories,namely non-magnetic isolation(T-type,separate type of teeth and yoke)and magnetic isolation(E-type,C-type).There are four kinds of stator modular structure,and the corresponding finite element(FE)machine models are established.In the case of 12 slot 10 pole and 12 slot 14 pole,the stator gap width and tooth tip structure are changed respectively to explore and compare the performance of different stator modular PM machines.Firstly,the winding theory of fractional-slot PM machine is deeply analyzed,including fractional slot concentrated winding(FSCW)and distributed winding,full tooth winding and separated tooth winding.The change of winding facto r after stator modularization is deduced,and the cogging torque generation mechanism and the condition of eliminating phase to phase coupling are given.Secondly,the general formula of slot pole coordination of FSCW machine is derived,the winding distribution of 12 slot 10 pole and 12 slot 14 pole are carried out,the stator and rotor structure dimensions of the modular machines are determined.Four different stator modular PM machines are designed,and the rationality of the designed machines are verified by the FE analysis software.Then,the electromagnetic and torque performance of different stator modular PM machines are simulated and compared.The influence of stator gap width on the performance of stator modular PM machines are studied,and the splicing of different modules and the heat dissipation of the machines are briefly introduced.It is found that the 12 slot 10 pole machine is more suitable to adopt C-type 2mm / 4mm modular structure to reduce cogging torque and torque ripple,while the 12 slot 14 pole machine is more suitable to adopt E-type 4mm modular structure to increase output torque or adopt C-type 2mm to reduce cogging torque and torque ripple.However,the cogging torque can be greatly reduced by the separate type of teeth and yoke in the non-magnetic isolation modular machine.Finally,the influence of two new tooth tip structures on the winding factor of the magnetic isolation modular machine are studied.It is found that 12 slot 10 pole are suitable for the structure of wound teeth have tooth tip,and 12 slot 14 pole are suitable for the structure of unwound teeth have tooth tip.The results show that 12 slot 10 pole machine is more suitable for the new type of tooth tip structure than 12 slot 14 pole machine.