铜包铝高频线圈损耗的理论计算方法

Theoretical Calculation on High-Frequency Loss of Copper Clad Aluminum Coil

为了在无线电能传输系统中,减小因高频电流趋肤效应和邻近效应产生的电阻损耗,提高线圈电能传输的利用率,针对铜包铝(CCA)线圈建立了电阻计算模型,分析导线内部电磁场的变化规律,同时结合电磁场边界条件,分别得到趋肤效应和邻近效应产生的交流电阻的解析计算表达式,通过仿真计算发现,在高频趋肤效应的影响下,体积分数较小的CCA导线的电阻值较大,随着频率的增大,趋肤效应增强,不同体积分数CCA导线的电阻值将趋于一致。在外界交变磁场的影响下,当频率较低时,纯铜导线内部涡流损耗密度较高,纯铜导线电阻大于CCA导线电阻,随着频率的增大,存在临界频率使二者电阻相等;当频率继续增大时,CCA导线内部涡流损耗密度增加,其电阻值大于纯铜导线。CCA导线周围的磁场强度分布与导线及磁场施加角度?有关,当?值(0°~360°)不同时,磁场强度以螺旋上升方式分布。根据实测高频下CCA导线线圈的电阻曲线,对比解析理论计算电阻曲线发现,解析表达式可满足实际测试要求,对高频下CCA导线的线圈损耗分析具有一定指导意义。

In order to improve the efficiency of power transmission in the wireless power transmission system and reduce the resistance loss caused by the high frequency current skin effect and the proximity effect,in this paper,the resistance calculation model for the double-layer composite copper clad aluminium(CCA)wire is established,and the changing law of the electromagnetic field inside the wire is also analyzed.At the same time,the analytical expressions of the AC resistance generated by the skin effect and the proximity effect are obtained in combination with the electromagnetic field boundary conditions.It is found that under the influence of high frequency skin effect,the CCA wire with smaller volume fraction has a larger resistance.As the frequency increases,the skin effect is enhanced,and the resistance values of CCA wires with different volume fractions will tend to be consistent.Under the influence of external alternating magnetic field,when the frequency is lower,eddy current loss density within pure copper wire is higher,and the resistance of pure copper wire is greater than that of CCA wire.With the continuous increase of frequency,the eddy current loss density inside the CCA wire increases,whose resistance is greater than pure copper wire.The magnetic field strength distribution around CCA conductor is related to the wire and the magnetic field applied angleθ.With differentθ(0°~360°),the magnetic field strength is distributed in a spiral way.Comparing the actual experimental curves of the high-frequency CCA coil resistance with the theoretical resistance calculation curves,the calculating results from analytical expressions are in accordance with the practical test results,which is valuable for the coil loss analysis in high-frequency CCA wire.