摘  要：理想的三相永磁无刷直流电动机是功率密度最高的一种电动机。实际上，由于三相永磁无刷直流电动机的相反电动势梯形波平顶宽度达不到120°E（°E表示电角度，下同），产生了原理性转矩波动，高功率密度的优势也受到影响。因此，多相永磁无刷直流电动机受到了重视。多相永磁无刷直流电动机的相反电势梯形波平顶宽度大于120°E，通过控制手段可以实现其高功率密度的优势；多相永磁无刷直流电动机是多台三相电动机的集成，它提高了系统的可靠性，改善了电动机性能，削弱了换相转矩波动；多相永磁无刷直流电动机提供了实现多个三相系统间是相互对称的，也可以是不对称的条件；还提供了多个三相系统的相电流不叠加的条件来减小蓄电池大电流放电。
关键词：永磁无刷直流电机；多相；优势

Abstract: The ideal 3 phase PM BLDCM is a kind of motor which has the highest power density.In fact,as the flat topped width of trapezoidal waveform of the phase BEMF of 3 phase PM BLDCM can not reach 120°E (°E equals to electronic angle,the same to the following),which makes the principle torque ripple appear,and the superiority of power density disappears as well, So pay more attention to the multiphase PM BLDCM. The flat topped width of trapezoidal waveform of phase BEMF of multiphase PM BLDCM is greater than 120°E, by means of control method,the advantage of superiority of power density can be realized.The multiphase PM BLDCM is the integrating system of multiple 3 phase motor,which enhance the reliability of system,improve the performance of the motor and weaken the commutating torque ripple. The multiphase PM BLDCM provides the condition of the realization of balance and unbalance of multiple 3 phase system,and provides the condition of  the phase current of multiple 3 phase system which do not add to reduce the discharge of high current of battery.
Key words: PM BLDCM; multiphase; advantages