摘  要：由于小功率永磁同步电机（PMSM）定子电阻很大，导致永磁体制动转矩较大，因而难于起动。外转子结构相对于内转子结构定子槽相对更小，转子部分转动惯量更大，起动更加困难。该文提出并设计了一种特殊结构的外转子异步起动PMSM，电机为400 W，8极外转子结构。电机采用场路结合方法设计。首先使用Ansys有限元程序求出电机设计的关键参数：空载气隙反电势，漏磁系数，交直轴同步电抗等。然后用编制的磁路计算程序计算电机的起动性能曲线。通过先后设计的两台样机实验，证明场路结合设计方法更可行。同时，分析表明小功率PMSM的磁路饱和度对其起动性能影响很大，为了保证能良好起动，应适当降低其饱和度。
关键词：外转子；异步起动PMSM；场路结合方法；起动性能

Abstract: It is difficult for low power line-start permanent magnet synchronous motor(namely PMSM)to reach synchronous speed because of big braking torque which is caused by big stator resistance.A novel external rotor structure line-start PMSM of 400 W and 8 poles was proposed.The motor was designed and investigated by the field-circuit combined method.Firstly,the air gap flux density,magnetic leakage coefficient,direct axis and quadrature axis synchronous reactances were calculated by Ansys finite element software.Then the starting characteristic curve was obtained by a compiled magnet circuit calculation program.Finally,the experiments of two protypes were carried out to prove the method above.The analysis shows that the saturation of the magnet circuit has a great influence on the starting characteristic of the low power line-start PMSM.
Key Words: External rotor；Line start PMSM；Field-circuit combined method；Starting characteristic