基于半桥和全桥斩波非导通相状态分析的BLDCM特性比较

摘要

According to states of non-conducting phase, the terminal voltage of non-conducting phase in Brushless DC Motor (BLDCM) was analyzed under half bridge chop (upper bridge chop) and full bridge chop control mode. Under half bridge chop mode, the voltage of the neutral point is zero with non-conducting phase ending free wheeling when the upper bridge chop switches off. Under this circumstance, the voltage of the lower bridge free wheeling diode of non-conducting phase is positive owing to electromotive fore (EMF) when it turns into negative value, which will produce braking current and torque in non-conducting phase, decrease valid power of BLDCM. Under full bridge chop, the voltage of the neutral point is a half of DC side voltage of Voltage Source Inverter(VSI). Under this circumstance, the voltages of two free wheeling diodes of the non-conducting phase are all negative. Non-conducting phase will not produce braking current and torque during its EMF transfers into negative value. Simulation results validate the performance of BLDCM under the two chop modes.%本文根据非导通相的状态,分析了无刷直流电机(BLDCM)半桥斩波(以上桥斩波为例)和全桥斩波控制方式下非导通相端口电压.半桥斩波中,上桥斩波关断时,非导通相正向续流结束后,中性点电压为零.此时非导通相反电动势过渡为负值后,下桥臂续流二极管在负的反电动势作用下正偏,将在非导通相中产生正向电流,使电机有制动电流和转矩,减小了有效出力.全桥斩波中,非导通相续流结束后,中性点电位为电压源逆变器(VSI)直流侧电压的一半,非导通相所在桥臂的上下两个续流二极管均处于反偏状态,不能导通.非导通相反电动势过渡期间,不会产生制动电流和转矩.仿真结果验证了两种斩波方式下BLDCM的运行特性.