电流谐波对永磁体涡流损耗的影响

Influence of Current Harmonics on Permanent Magnet Eddy Current Loss

永磁同步电机应用于高速铁路牵引领域,要求电机具有高起动加速性能和宽调速范围。驱动电机的牵引逆变器最大开关频率一般为500 Hz,电压波形的畸变导致输出电流谐波含量大,在永磁体中产生涡流损耗,导致永磁体局部过热甚至产生不可逆退磁。文中分析涡流损耗的来源和计算方法,针对电流谐波产生的永磁体涡流损耗,基于实际测量电流波形分析电流谐波涡流路径、各次谐波涡流损耗的大小、永磁体槽口深度hr与涡流损耗的关系及分段与涡流损耗的关系。分析结果表明:电流谐波是产生永磁体涡流损耗的主要原因,主要为2次、5次、7次、11次、13次电流谐波;低速工况涡流损耗高于高速工况,这与低速工况5次、7次电流谐波幅值较大成正相关;采用分段后,电流谐波产生的涡流损耗大大降低,最佳轴向、径向分段数为6~8段。分析结果为牵引逆变器驱动的永磁同步电机降低电流谐波产生的永磁体涡流损耗以保障电机的安全运行提供了参考。

PMSMs are used in high-speed railway traction,requiring motors to have high starting acceleration performance and wide speed range.The maximum switching frequency of the traction inverter is generally 500 Hz.The output voltage waveform distortion causes that the current harmonic content is large.Current harmonics produce eddy current losses,resulting in local overheat,even causing irreversible demagnetization.In this paper,the source and calculation method of eddy current loss is analyzed.Based on the measured current,the eddy current path,the relationship between the harmonic amplitude,the permanent magnet slot opening depth hr,the radial and axial segments and eddy current loss are analyzed.The analysis results show that the current harmonic is the main reason of eddy current loss,mainly 2th,5th,7th,11th,13th current harmonics.The eddy current loss is higher in low speed than in high speed.This is positively correlated with 5th,7th current harmonic amplitude of low speed.After segmentation,the eddy current loss is greatly reduced,and the optimum radial and axial segment is 6 to 8 segments.Analysis result is a reference of PMSMs driven by traction inverters reducing eddy current losses to ensure the safe operation.