一种消除直线永磁无刷直流电机边端效应对换相时机影响的方法

电磁弹射用直线永磁无刷直流电机的永磁体动子具有开断结构,使动子边端的磁场分布发生变形。当采用霍尔元件检测磁场实现换相时,这种边端效应就会影响换相时机。分析了这类电机的换相机理和动子开断结构对换相时机的影响,指出这类边端效应受极弧系数影响显著,并提出了利用不对称滞环比较器或简易单限比较器对霍尔输出信号进行处理从而消除这类边端效应影响的方法,实验验证了简易单限比较器方案的可行性。

A Method to Eliminate the Influence on Phase Change Points Caused by the End Effect of the Linear PM BLDC Motor

The linear PM BLDC motor(LPMBLDCM) used in an electromagnetic launcher has a short broken permanent magnet(PM) mover whose end magnetic field is deformed. When hall cells are used in detecting magnetic induction and helping realize phase change, the phase change points(PCPs) will be shifted by this type of end effect. The phase change principle of the LPMBLDCM was analyzed and how the short broken PM mover shifts the PCPs was presented. It was concluded that this type of end effect is mainly affected by the pole-arc factor of the PM poles. An asymmetric hysteresis comparator, as well as a common single threshold comparator, was used to reshape the output of hall cells to eliminate the influence caused by the end effect. Experiment results of a prototype motor prove that the common single threshold comparator method is feasible.