When a pipe is partially filled with a given working liquid,the relationship between the electromotive force(EMF)measured by the sensor(flowmeter)and the average velocity is nonlinear and non-monotonic.This relationsh...When a pipe is partially filled with a given working liquid,the relationship between the electromotive force(EMF)measured by the sensor(flowmeter)and the average velocity is nonlinear and non-monotonic.This relationship varies with the inclination of the pipe,the fluid density,the pipe wall friction coefficient,and other factors.Therefore,existing measurement methods cannot meet the accuracy requirements of many industrial applications.In this study,a new processing method is proposed by which the flow rate can be measured with an ordinary electromagnetic flowmeter even if the pipe is only partially filled.First,a B-spline curve fitting method is applied to a limited set of measurements.Second,matrix inversion required in the B-spline curve method is optimized in order to reduce the number of needed computations.Dedicated experimental tests prove that the proposed method can effectively measure the average flow velocity of the fluid.When the fluid level of the pipeline is between 50%and 100%,the relative error is less than 3.5%.展开更多
针对电磁发射领域短初级直线感应电机(short primary linear induction motor,SPLIM)的纵向端部效应引起的感应电势不对称现象,首先基于一维场理论分别对正序和负序电流激励条件下的SPLIM气隙电磁场进行推导及计算分析,得到气隙电磁场...针对电磁发射领域短初级直线感应电机(short primary linear induction motor,SPLIM)的纵向端部效应引起的感应电势不对称现象,首先基于一维场理论分别对正序和负序电流激励条件下的SPLIM气隙电磁场进行推导及计算分析,得到气隙电磁场解析表达式,并将其计算与有限元计算值比较,结果表明,解析计算值与有限元结果精度相当。然后给出基于气隙磁密和绕组分布函数的感应电势计算方法,同时给出对称电压激励条件下初级绕组感应电势的计算流程,并通过有限元和试验进行验证。在以上分析基础上,将气隙磁密分解为基本行波磁密、入端正向行波磁密、出端反向行波磁密3部分,深入分析感应电势不对称机理以及感应电势不对称随系统设计变量变化规律。提出的基于磁密分解和绕组函数计算感应电势的方法,可为此类电机的设计、分析、控制提供一种新的思路。展开更多
为了研究无刷直流电机(brushless DC motor,BLDCM)电枢电流对转子温升的影响,提出一种涡流电势分类估算法。将电枢电流分解为直流分量iDC和交流分量iAC,在空间上,运动的转子会在绕组直流分量iDC的磁动势作用下产生运动电势em;同时在时间...为了研究无刷直流电机(brushless DC motor,BLDCM)电枢电流对转子温升的影响,提出一种涡流电势分类估算法。将电枢电流分解为直流分量iDC和交流分量iAC,在空间上,运动的转子会在绕组直流分量iDC的磁动势作用下产生运动电势em;同时在时间上,绕组交流分量iAC的磁动势也会在转子中产生感应电势et。暂不考虑涡流反应,对11kW无刷直流电机典型工作点下,选择转子中最大闭合曲线和最大曲面分别计算运动电势em和感应电势et。在不考虑齿槽影响的前提下,得到运动电势远小于感应电势的结论,认为只要电枢电流连续,负载变化对转子温升影响不大。实验结果验证了上述观点。展开更多
基金the Science and Technology Project of Education Department of the Guangdong Province,China(2017GKTSCX079)Science and Technology Project of Zhongshan Polytechnic,China(2018G01).
文摘When a pipe is partially filled with a given working liquid,the relationship between the electromotive force(EMF)measured by the sensor(flowmeter)and the average velocity is nonlinear and non-monotonic.This relationship varies with the inclination of the pipe,the fluid density,the pipe wall friction coefficient,and other factors.Therefore,existing measurement methods cannot meet the accuracy requirements of many industrial applications.In this study,a new processing method is proposed by which the flow rate can be measured with an ordinary electromagnetic flowmeter even if the pipe is only partially filled.First,a B-spline curve fitting method is applied to a limited set of measurements.Second,matrix inversion required in the B-spline curve method is optimized in order to reduce the number of needed computations.Dedicated experimental tests prove that the proposed method can effectively measure the average flow velocity of the fluid.When the fluid level of the pipeline is between 50%and 100%,the relative error is less than 3.5%.
文摘针对电磁发射领域短初级直线感应电机(short primary linear induction motor,SPLIM)的纵向端部效应引起的感应电势不对称现象,首先基于一维场理论分别对正序和负序电流激励条件下的SPLIM气隙电磁场进行推导及计算分析,得到气隙电磁场解析表达式,并将其计算与有限元计算值比较,结果表明,解析计算值与有限元结果精度相当。然后给出基于气隙磁密和绕组分布函数的感应电势计算方法,同时给出对称电压激励条件下初级绕组感应电势的计算流程,并通过有限元和试验进行验证。在以上分析基础上,将气隙磁密分解为基本行波磁密、入端正向行波磁密、出端反向行波磁密3部分,深入分析感应电势不对称机理以及感应电势不对称随系统设计变量变化规律。提出的基于磁密分解和绕组函数计算感应电势的方法,可为此类电机的设计、分析、控制提供一种新的思路。
文摘为了研究无刷直流电机(brushless DC motor,BLDCM)电枢电流对转子温升的影响,提出一种涡流电势分类估算法。将电枢电流分解为直流分量iDC和交流分量iAC,在空间上,运动的转子会在绕组直流分量iDC的磁动势作用下产生运动电势em;同时在时间上,绕组交流分量iAC的磁动势也会在转子中产生感应电势et。暂不考虑涡流反应,对11kW无刷直流电机典型工作点下,选择转子中最大闭合曲线和最大曲面分别计算运动电势em和感应电势et。在不考虑齿槽影响的前提下,得到运动电势远小于感应电势的结论,认为只要电枢电流连续,负载变化对转子温升影响不大。实验结果验证了上述观点。
