环形绕组无刷直流电机负载换向的解析模型

环形绕组无刷直流(CWBLDC)电机是一种具有梯形波反电动势的多相永磁电机,相应的换向驱动电路可实现相电流的换向。由于该电机采用梯形波反电动势,铁心材料的利用更加充分,能获得高于永磁同步电机(PMSM)的转矩密度;另一方面,采用极、槽数优化设计的分数槽绕组,能够有效抑制电机的转矩脉动,使其接近永磁同步电机的水平。良好的换向性能是该电机得以应用的前提,本文提出一种负载换向方法,其利用负载本身的电压即电机反电动势来改变相电流的方向,能够实现功率开关的零电流关断。以一台2极12槽环形绕组无刷直流电机为对象,详细分析了负载换向的过程,建立了换向过程的解析模型,讨论了换向提前角的确定方法。采用场路耦合仿真分析了该电机的换向过程,验证了解析模型的准确性,最后由原理样机试验验证了负载换向原理的可行性。

Analytical Model of Load Commutation of the Circular Winding Brushless DC Machine

A circular winding brushless DC (CWBLDC) machine is a multiphase brushless dc machine with the associated commutation circuit.It can achieve higher torque density than permanent magnet synchronous machines (PMSMs) since the iron core is more fully utilized with trapezoidal flux density in air-gap.Based on the proper pole/slot number,it can effectively reduce commutation torque ripple.The commutation circuit should be properly controlled which is the key of the machine.This paper presents a load commutation method for CWBLDC machine,which relies on the EMF of its load (the motor) to reverse the phase current direction.Power devices of the commutation circuit can be turned off with no current flowing through,which can be considered as a form of soft switching.The analytical method of the machine which considers commutation process is derived and critical conditions for successful commutations are highlighted.Field-circuit coupled analysis and experiment results have been performed to verify the load commutation method.